Product Design

´ gico y de Estudios Superiores de Monterrey Instituto Tecnolo Campus Toluca

Preface

Product design: techniques for robustness, reliability and optimization

Class Notes Dr. Jos´ e Carlos Miranda V.

It is widely recognized that to develop successful products, systems or services it is extremely important to follow a structured product development process. Although each company follows a process tailored to its specific needs, in general the start of a product development process is the mission statement for the product. It identifies the target markets for the product, provides a basic functional description of the product, and specifies the key business goals of the effort. The end of the development effort occurs when the product is launched and becomes available for purchase in the market place. The different activities that take place during the product development process can be grouped into five phases: Concept development, system-level design, detail design, testing and refinement, and production ramp-up. During the detailed design and the testing and refinement phases, product optimization, robustness and reliability becomes critical. As many powerful techniques have appeared to make a product more optimal, robust and reliable, it is necessary to know how they work and how can they be applied to design products that exceed customer expectations and minimize costs. The present notes have been prepared for the courses of Design Methodologies and Product Design that I teach. Although these notes are far from complete and therefore may contain many mistakes and inaccuracies, they evolve term after term and with the help and suggestions of my students are continuously improved. Once these notes are mature, it is my desire to publish them to reach a wider audience and receive further comments. If you have any feedback, suggestions or have detected any mistakes, or simply would like to assist me or contribute in this effort, please do not hesitate to contact me. I will be very happy to hear from you.

v. Fall 2004

c Copyright 2004 Dr. Jos´ e CarlosMiranda. Todos los derechos reservados.

Jos´e Carlos Miranda Research Center for Automotive Mechatronics [email protected] c Copyright 2004 Dr. Jos´ e CarlosMiranda. Todos los derechos reservados.

CHAPTER

1

The Engineering Design Process

Part I The product design process

1.1

Definition of design

The word design has had different meanings over the last decades. While sometimes a designer is considered to be the person drafting at the drawing board or in the computer, the word design really conveys a more engineering and analytical sense. Design is much more than just drafting. Suh (1990) defines design as the creation of synthesized solutions in the form of products, processes or systems, that satisfy perceived needs through the mapping between functional requirements and design parameters. In the scope of the previous definition, functional requirements (FRs) respond to the question of what a product must do or accomplish. On the other hand, design parameters (DPs) respond to the question of how the functional requirements will be achieved. What relates the domain of functional requirements to the domain of design parameters is design (see figure 1.1). It should be noted that although design parameters should fulfill the functional requirements, the mapping between them is not unique. For a set of functional requirements may be several design parameters that fulfill those functional requirements. Another, less technical, definition of design is the one promulgated by ABET (Accreditation Board for Engineering and Technology): c Copyright 2004 Dr. Jos´ e CarlosMiranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e CarlosMiranda. Todos los derechos reservados.

3

1.2 The design process WHAT?

1.2 The design process

4

HOW? Mechanical Engineering

List of Functional Requirements

design

List of Design Parameters

Electronic Engineering

Purchasing Product Design

Manufacture Engineering

Marketing

Figure 1.1: Design is the process of mapping functional requirements to design parameters.

“Engineering design is the process of devising a system, component, or process to meet desired needs. It is a decision making process (often iterative) in which the basic sciences, mathematics and engineering sciences are applied to convert resources optimally to meet a stated objective. Among the fundamental elements of design process are the establishment of objectives and criteria, synthesis, analysis, construction, testing and evaluation. . . It is essential to include a variety of realistic constraints such as economic factors, safety, reliability, aesthetics, ethics and social impacts.”

Industrial Design

Figure 1.2: Engineering design core disciplines. 1.2.1. Design process Probably the most simple model of the design process models is the one shown in figure 1.3, where only four general stages are outlined. Another relatively simple model is presented by Ullman (1992) who suggest to view the design as problem solving. When solving a given problem, five basic actions are taken: 1. Establishment of need or realize there is a problem to be solved.

Although several definitions of design may be found, the last one highlights one of the main difficulties associated with design: its truly multidisciplinary nature. Design involves several, if not all, different departments in a given company (see figure 1.2). Design engineers should always be aware of this condition, involving in the design process the expertise of people of different disciplines.

1.2

The design process

2. Understanding of the problem. 3. Generation of potential solutions for it. 4. Evaluation of the solutions by comparing the potential solutions and deciding on the best one. 5. Documentation of the work. While it is possible to see design as problem solving, it is important to realize that most analysis problems have one correct solution whereas most design problems have many satisfactory solutions.

There are many different maps or models of the design process. Some of these models describe steps and their sequence as they occur in the design process. Some other models try to define or prescribe a better or more appropriate pattern of activities. Cross (1994) describe some of these models.

A more detailed model, which involves all steps of the design process, is presented in figure 1.4. As shown, this model divides design process in 5 phases: Concept development, System-Level design, Detail design, Testing and refinement and Production. Each phase has one or more steps. It is important to realize that this model is general and may be necessary to follow different paths in one or more phases depending on the project at hand.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

5

1.2 The design process

1.2 The design process Phase 1: Concept Development

Recognition of need

Exploration

Conceptualization Phase 2: System-Level Design

Generation

6

Feasibility assessment

Phase 3: Detail Design

Preliminary design cost analysis / redesign

Evaluation Development testing

Phase 4: Testing and Refinement

Communication

Detailed design Qualification testing

Production planning and Tooling design

Phase 5: Production

Acceptance testing

Production

Figure 1.3: A simple model of the design process with 4 stages. Figure 1.4: Detailed model of the design process. Independently of the model, it is generally agreed that the design process should always start with the recognition of a need. After the need has been recognized it is necessary to consider alternatives for its solution, which is done during the concept development phase. Here the statement of the problem is taken and broad solutions to it are generated. This phase presents the greatest chance for improvements and hence is specially imperative to be objective, open to new ideas and recognize when changes are needed. Once the best ideas have been selected, preliminary design may start to further evaluate those ideas. In this phase testing may be of great help to differentiate good ideas from regular ones. After a design has been finally selected, detailed design begins to incorporate every feature that the design may need to incorporate. Hence, a very large number of small but essential points should be decided. After the detailed design has been re-evaluated and tested, production planning may be started and final products tested for final acceptance. In what follows the different steps in the design process are discussed more in depth. 1.2.2. Identifying customer needs

The need to design a new product may come from different sources: consumers, organizations or governments. The need may also sometimes

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

be substituted for an idea of a product with possibilities of becoming commercially successful. Eide et al. (1988) state that in industry, it is essential that products sell for the company to survive. Inasmuch as most companies exist to make a profit, profit can be considered to be the basic need. Hence, a bias toward profit and economic advantage should not be viewed as a selfish position because products are purchased by people who feel that they are buying to satisfy a need which they perceived as real. The consumers are ultimately the judges of whether there is truly a need. Identifying the needs of the costumer is one of the most important steps in the design process and is, at the same time, one of the most difficult since is not unusual to find that the customer does not know exactly what features the product must have. Once the needs have been specified together with the costumer, this information is used to guide the design team in establishing design parameters, generating concepts and selecting the best one of them. According to Ulrich & Eppinger (2000) the process of identifying customer needs includes five steps: 1. Gather raw data from customers. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

7

1.2 The design process Metric

Value

The product must be . . . easy to install

Average time for installation < x seg.

durable

Must withstand 10x cycles

easy to open

Opens with a force of max. x newtons.

able to resist impacts

Withstand drops from x meters.

able to work in cold weather

Operation possible at -x◦ C.

1.2 The design process

8

According to French (1985) in this phase the statement of the design problem is taken and broad solutions are generated in the form of schemes. It is the phase that makes the greatest demands on the designer, and where there is more scope for striking improvements. It is the phase where engineering science, practical knowledge, production methods and commercial aspects need to be brought together. It is also the stage where the most important decisions are taken. 1.2.4. Concept generation

2. Interpret the raw data in terms of customers needs.

In the scope of design, a concept is an abstraction, an idea that can be represented in notes and/or sketches and that will eventually become a product. It is generally recognized that, for a given product, several ideas (sometimes hundreds of them) should be generated. From this pool of ideas, a couple of them will merit serious consideration for further evaluation and development.

3. Organize the needs into a hierarchy of primary and secondary needs.

The concept generation stage can be divided into 4 steps:

Table 1.1: Examples of metrics and their value.

4. Establish the relative importance of the needs. 5. Reflect on the results and the process.

1. Clarification of the problem. 2. Gathering of information.

As was briefly discussed above, when the design engineer is first approached with a product need, it is very unlikely that the customer will express clearly what is needed. In most occasions it is only know what is wanted in a very general way without idea of the particularities involved. 1.2.3. Establishing the design requirements

Hence, the starting point for a design engineer is to turn an ill-defined problem with vague requirements into a set of requirements that are clearly defined. This set of product requirements may change as the project advances, so it is convenient to clarify them at all stages of the design process. For the product requirements to be helpful, they must be translated to technical specifications that are precise, easily understood and can be measure by means of one or more design variables. Ulrich & Eppinger state that “A specification consists of a metric and a value.” Table 1.1 shows some examples of metrics and their values.

3. Use and adaptation of design team’ s knowledge. 4. Organization of team’s thinking. Although concept generation is an inherently creative process, it is possible to use some techniques to improve it like functional decomposition and generation of concepts from functions. Although sources for conceptual ideas come primarily from the designer’s own expertise, it can be enhanced through the use of books, experts, lead engineers, patent search, brainstorming and current designs. The purpose of concept selection is assessing the feasibility of concepts to ensure that they are achievable technically and economically. The feasibility of the concept is based on the design engineer’s knowledge. As in the generation of concepts, the design engineer can rely in tools –like the decision-matrix method– to compare and evaluate concepts. 1.2.5. Concept selection

Several tools can be used to establish product specifications. Although simple to apply, the objectives tree and decision tree methods offer a clear and useful starting format for such a statement of requirements and their relative importance. As will be discussed later, other more sophisticated and more useful method is Quality Function Deployment (QFD).

The importance of the concept selection phase cannot be understated. It is known that decisions made during the design process have the greatest effect on the cost of a product for the least investment. In figure 1.5, the cost of design and its influence in manufacturing cost for an automotive project

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

1.2 The design process Overhead 100

Labor Material

Percent

80

Design

1.2 The design process Design changes

9

10

Company A

60

Company B

40 20 0 Final Manufacturing Cost

Influence on Final Manufacturing Cost

Figure 1.5: Design influence on manufacturing cost (After Ullman, 1992). is shown. From the figure it can be stated that the decisions made during the design process have the greatest effect on the cost of a product for the least investment. Typically, around 70% to 80% of the manufacturing cost is committed by the end of the conceptual phase of the design process. Hence the importance of concept evaluation. Also, the generation and evaluation of concepts have a great effect on the time it takes to produce a new product. Figure 1.6 shows the number of design changes made by two automobile companies with different design strategies. Company A made many changes during the early stages of the design process as a result of the iterative process of generation and evaluation of concepts. Company B made just a few changes in the initial stage, but was still making changes later in the process, even when the product was released for production. The advantage gained by company A is clear since changes made late in the process are far more expensive than changes made in early stages. The evaluation of concepts to find its viability may occur not only during concept development, but throughout the design process. This will lead to the so called Design process paradox (Ullman, 1992). The design process paradox states that during the design process, the knowledge about the design increases as the project runs in time and the design team gains understanding of the problem at hand. Hence, the knowledge of the design team is at its top when c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Begin design

Release for production

Time

Figure 1.6: Engineering changes in automobile development (After Ullman, 1992).

the design process is at its end. Although this seems natural, it is important to realize that, by the end of the process, most decisions have already been made. This increased knowledge at the end of the project tempt most design teams to feel the need of re-doing the project now that they fully understand it. Unfortunately, economics almost always drive the design process, and second chances rarely exist. Figure 1.7 shows the dilemma above. At the beginning of the process, the design team has the most freedom since no decisions have been made. As time goes by, knowledge increases as a result of the design time efforts, but freedom is lost since decisions have been made and changes are increasingly expensive to perform. Concept testing is closely related to concept selection. It is used to gather opinions and information from potential customers about one or more of the selected concepts that may be pursued. It can also be used gather information about how to improve an specific product and to estimate the sales potential of the product.

1.2.6. Concept testing

Ulrich & Eppinger (2000) suggest to divide the concept testing into 6 steps: c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

11

1.2 The design process 100

Knowledge about the design problem

1.2 The design process

12

integration between different engineering disciplines involved on the design effort.

80

The preliminary design helps to obtain more precise design requirements involving analysis, benchmarking, literature search, experience, good judgment and, if necessary, testing. The refinement of the project also helps to have a better estimate of the project cost and required time for completion.

Percent

60 40 Design freedom

20 0 Time into design process

Figure 1.7: The design process paradox (After Ullman, 1992). 1. Definition of the purpose of the concept test. 2. Choosing of a survey population. 3. Choosing of a survey format. 4. Communication of the concept. 5. Measurement of customer response. 6. Interpretation of results. Both concept selection and concept testing are used to narrow the possible concepts under consideration. Concept selection relies in the work and judgment of the development team. Concept testing is based in data gathered directly from potential customers.

After the preliminary design stage has been carried out, it is necessary to go into the details of the design in order to better understand the concepts. Detail design is mostly concerned with the design of the subsystems and components that make up the entire design. Because of the latter, this stage is sometimes divided into two independent parts, System-level design and the detail design itself. 1.2.8. Detailed design

In the system-level design the product arquitecture is defined and decomposition of the product into subsystems and components takes place. These components may be integrated circuits, resistors, shafts, bearings, beams, plates, handles, seats, etc., depending on the nature of the product under development. Here, geometric layouts of the product and functional specifications for each subsystem are stated. The detail design phase includes the complete specification of each independent part such as geometry, materials and tolerances and identifies all those parts that will be purchased from suppliers. In this stage, the control documentation of the product is generated, including technical drawings, part production plans and assembly sequences. This stage initiates with the identification of the machines, tooling and processes required to manufacture the designed product. Technical data such as dimensions, tolerances, materials and surface finishes among others are evaluated to determine the appropriate assembly sequence for the manufacturing operations. According to Ertas and Jones (2000), typical tasks included in the production planning include: 1.2.9. Production planning

The preliminary design stage or embodiment design stage, fills the gap between design concept and detailed design. According to French, in this phase the schemes are worked up in greater detail and, if there is more than one, a final choice between them is made. There is (or should be) a great deal of feedback from this phase to the conceptual design phase. 1.2.7. Preliminary design

Is during this stage of the design process that the overall system configuration is defined. Extensive engineering documentation in the form of schemes, diagrams, layouts, drawings, notes or other types of documents is generated to provide control over the project and to ensure better communication and c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

1. Interpretation of design drawings and specifications. 2. Selection of material stock. 3. Selection of production processes. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

13

1.2 The design process

1.3 Quality Function Deployment

14

4. Selection of machines to be used in production. With QFD Effort

5. Determination of the sequence of operations. 6. Selection of jigs, fixtures, tooling and reference datum.

Traditional approach

7. Establishment of tool cutting parameters, such as speed, depth and feed rate. 8. Selection of inspection gauges and instruments. 9. Calculation of processing time. 10. Generation of process documentation and numerically controlled machine data. Once the production planning has been made and all the decisions regarding production have been taken, a production ramp-up is made using the intended production system. The purpose of the production ramp-up is to evaluate the correctness of the production plan, the tooling and the assembly sequences to follow as well as to identify possible flaws before going to a full-scale production. Engineers feel most of times burdened with the idea of documenting their designs. The preparation of documents describing the design process and the reasons behind decisions taken is oftenly seen as as an activity that does not directly contribute to the design. Other times documentation is seen as an unattractive task that does not involve any challenge at all. 1.2.10. Documentation

Nevertheless, documentation is as important as any other in the task in the design process. Product documentation is important not only in terms of instructions to user, maintainers or others, but is imperative for purposes like legal protection or future product redesign. Hence, keeping track of the ideas developed and decisions made in a design notebook is essential. It is advisable to keep, for patent or legal purposes, a notebook with dated pages that is sequentially numbered and signed. In this notebook, all information related to the design such as sketches, notes, calculations and reasons behind decisions should be included. The notebook does not have to be neat, but certain order has to be kept. When design information like plots, photocopies, drawings or results of analyses are too large or bulky to keep in the notebook, a note stating what the document is, a brief summary of its contents and where it is filed should be written. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Time Design

Details

Process

Production

Figure 1.8: Traditional vs. QFD design approaches (After Ouyang et al. When the design effort has concluded, standard drawings or computer data files of components showing all the information necessary for the production of the product have to be generated. This drawings usually include written documentation regarding manufacturing, assembly, quality control, inspection, installation, maintenance and, retirement.

1.3

Quality Function Deployment

It is not uncommon that designers find themselves working a problem only to find out later that they were solving the wrong one. An efficient designer must try by all possible means to define the correct problem at the beginning or discover the problem at earliest possible moment. The Quality Function Deployment technique provides a methodological way to do it. Quality Function Deployment (QFD) originated in Japan as a help to translate customer requirements into technical requirements throughout the development and production of a product. It originated in Japan in the 1970’s as the Kobe supertanker company wanted to develop the logistics for building complex cargo ships. Professors were asked to create a technique that would ensure that each step of the construction process would be linked to fulfilling a specific customer requirement. Using this technique, Toyota was able to reduce the costs of bringing a new car c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

15

1.3 Quality Function Deployment

1.3 Quality Function Deployment

16

Design Requirements

HOWS

3 Process

WHATS

Details

3. Determining relative importance of the requirements.

Process Requirements

Product Requirements

HOWS

2

WHATS

Design

2. Determining customer requirements.

Parts Requirements

Parts Requirements

1

WHATS

HOWS

1. Identifying the customer(s).

Design Requirements

WHATS

Customer Requirements

HOWS

The QFD technique uses six steps to do this translation:

Production Requirements

4

4. Competition benchmarking. 5. Translating customer requirements into measurable engineering requirements. 6. Setting engineering targets for the design.

Production

Figure 1.9: The four phases of QFD. From customer requirements to client satisfaction. The hows on each House of Quality becomes the whats in the next.

model to the market by 60 percent and to decrease the time required for its development by one third. As shown in figure 1.8, QFD requires more effort on the design stage, but as most design flaws are catched early in the design process, later stages are less prone to fail or require adjustments or redesigns. According to Ouyang et al., Qualify Function Deployment has four distinct phases: design, details, process and production. As shown in figure 1.9, in the Design phase, the customer helps to define the requirements for the product or service. In the Details phase, design parameters (hows) carried over the design phase become the functional requirements (whats) of individual part details. In the Process phase, the processes required to produce the product are developed. Once more, the design parameters of the details phase become the functional requirements of the process phase. Finally, in the Production phase, the design parameters of the process phase become functional requirements for production.

Each step will be reviewed in more detail, but before going any further is convenient to highlight that: • No matter how well a design team thinks it understand a problem, it should employ the QFD method. • Customer requirements must be translated into clear engineering targets involving measurable quantities. • The QFD technique may be applied to the whole design as well as to subsystems or subproblems. • It is important to first worry about what needs to be designed and, once the problem is fully understood, to worry about how it will be designed. 1.3.1. Identification of costumers

Sometimes is not only not clear what the customer wants, but also who the customer is. Furthermore, is very common to find that there is more than one

customer to satisfy.

As discussed above, QFD can be applied all the way through the design process from concept to production using the same principles on each phase. It is generally agreed that the QFD technique is most valuable at the early design stages where customer requirements have to be translated to engineering targets.

Independently of how many customers may be, it is essential to realize that the customer, and not the engineer, is the one driving the product development process. Many times the engineer has a mental picture of how the product should be like and how it should perform, picture that may be very different from what the customer really wants. On the other hand, may products have been poorly received by the customers simply because the engineer failed to identify accurately the customers’ desires.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

17

1.3 Quality Function Deployment

The determination of customer requirements should be made through customers surveys or evaluation of similar existing products. Customer requirements should be made in the customer’s own words such as “fast”, “easy”, “durable”, “light”, “strong”, etc. As much as possible, customer requirements should be stated in positive terms. 1.3.2. Determination of costumers requirements

In order to facilitate understanding, requirements may be grouped in types like performance requirements, appearance requirements, safety requirements, and so on. If the customer has specific preference for one given type, determining the relative importance of different requirements may be easier to do.

Not all requirements will be regarded as equally important to customers. For example, “easy to use” may be more important for the customer than “easy to maintain”, and “easy to maintain” may be regarded as more more important than “good looking”. On the other hand, some requirements like “safe to use”, may be regarded as absolute requirements rather than relative preferences. 1.3.3. Determination of relative importance of the requirements

In order to design effectively, the design team should know which attributes of their product design are the ones that most heavily affect the perception of the product. Hence, it is necessary to establish the relative importance of those attributes to the customers themselves.

Sometimes customers often make judgment about product attributes in terms of comparisons with other products. One screwdriver, for example, may have better grip than others or another screwdriver may seem more durable. Given that customers are not generally experts, they may compare different attributes by observation of what some products achieve.

1.3.4. Competition benchmarking

1.4 Some important design considerations

18

1.3.5. Conversion of Once a set of customer requirements have been customer needs into selected due to its importance, it is necessary to engineering requirements develop a set of engineering requirements that are measurable. Some of these engineering requirements, or design specifications, may be cleared defined from the beginning. One example is the weight that a chair must withstand. Others, may be more difficult to characterize as will be measurable by different means. In the case of a chair that is to be “easily assembled” by the customer, “easily” may be measured in terms of the number of tools needed for the assembly, the number of parts to be assembled, the number of steps needed for the assembly or the time needed for the assembly. In this step, every effort should be made in order to find all possible ways in which a customer requirement may be measured. The last step in the process is setting the engineering targets. For each engineering measure determined in the previous step, a target value will be set. This target values will be used to evaluate the ability of the product to satisfy customer requirements. Two actions will be needed, to examine how the competition meets the engineering requirements, and to establish the value to be obtained with the new product. 1.3.6. Setting engineering targets

Best targets are established using specific values. Less precise, but still usable, are those targets set within some range. Another type, extreme values, are targets set to a minimum or maximum value. Although extreme type targets are measurable, they are not the best since they give no clear information of when the performance of a new product is acceptable. Here, evaluation of the competition can give at least some range for the target value.

1.4

Some important design considerations

If the product is to be well positioned in a competitive market, the design team must ensure that its product will satisfy customer requirements better than competitor products. Therefore, the performance of the competition of those product attributes that are weighted high in relative importance should be analyzed.

When designing products, several considerations must be taken into account. For the inexpert designer, this considerations may or may not be obvious sources for requirements, parameters and targets. In what follows, three design considerations, whose importance may depend on the project at hand, are briefly discussed.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

19

1.4 Some important design considerations

1.5 Good design practices

Most of the times, when designing a new product, the design team does not pay much attention in how the product will be distributed. Decisions regarding packaging, transportation and shelf stocking are taken after the product has been designed. Nevertheless, design features that could be avoided may increase the distribution cost due to the need of special packaging, transportation or shelfs. Design teams must do everything at their hands to avoid this situations that unnecessarily increase the cost of the product.

process from early stages.

1.4.1. Product distribution

Taking into account the distribution of the product is specially important when redesigning a product. Generally speaking, companies looking for an existing product of better features are unwilling to make extensive modifications to the existing distribution infrastructure. In this cases, product distribution will be a major source of requirements. It is normally assumed for most engineering products, that after it has completed its useful life, the product will be removed from its original installation, retired and dispose of. Nevertheless, in many occasions the product is put to some second use that is different from its original purpose. Consider for example, an empty 20 lts. (4 Gal.) bucket that is used as a step. 1.4.2. Design for after life

The problem arises as this second use was not included in the initial design specifications and is therefore not accounted for in the design process. The result may be failure and personal injury leading to product liability litigation. The fact that a certain product was used in a way never intended by the original design may not be of importance on the court. Courts seem to focus on whether the failure was foreseeable and not whether there was negligence or ignorance. The best the design team can do is to try to foresee both use and misuse an make provision in the design for credible failures.

In order to translate functional requirements into design parameters, the study of ergonomics has produced a body of anthropometric (human measure) data that can be used in designing anything that involves interaction between a human and a product. As anyone will agree, humans bodies come in a variety of shapes and sizes, which makes somewhat difficult to design a product to fit absolutely everybody. Nevertheless, human measure can be well represented as normal distributions. This last feature makes it possible to define parameters to fit, let say, 90% percent of the population. In many occasions, to be able to design for such a high percentage of the population it is required to include adjustable features to the product. One typical example is the way in which seat and steering wheel positions can be altered in many cars to adapt the height and size of the driver. Other three ways in which humans may interact with products is as a source of power (for example when opening a door), as a sensor (for example reading a dashboard) or as a controller (for example the operating a CD player). In the first case, information about the average force that a human can provide (or is expected to provide) is vital toward a successful product. In the second case, if the human is expected to be able to read information is important that the person has only one way to interpret the data. In the third way, a product must be designed so there is no ambiguities in the form in which the product operates. For the product to be easy to interact with, there must be only one obviously correct thing to do for every action that is required.

1.5 Almost every product that is designed will interact with humans whether during manufacture, operation, maintenance, repair or disposal. Operation is probably the most important since it will involve the largest span of interaction. 1.4.3. Human factors in design

20

Good design practices

Considering operation, a good product will be the one that becomes an extension of the user’s motor and cognitive functions. To achieve this, human– machine interaction features should be included as parameters in the design

1.5.1. Good design versus The goal for the introduction of models for the bad design design process is to provide a guideline to help the engineer/designer to achieve a better product through the use of good design practices. As experience would tell, in most occasions it is not difficult to tell either as engineer or consumer, a good design from a bad design. Table 1.2 show some general characteristics of good design versus bad design.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

21

1.5 Good design practices

Good Design

Bad Design

1. Works all the time

1. Stops working after a short time

2. Meets all technical requirements

2. Meets only some technical requirements

3. Meets cost requirements

3. Costs more than it should

4. Requires little or no maintenance

4. Requires frequent maintenance

5. Is safe

5. Poses a hazard to user

6. Creates no ethical dilemma

6. Fulfills a need that is questionable

Table 1.2: Characteristics of good design versus bad design. After Horenstein (1999). 1.5.2. Good design engineer versus bad design engineer

Horenstein (1999) highlights the traits of good design engineer and bad design engineers. According to Horenstein, a good engineer:

• Listens to new ideas with an open mind. • Considers a variety of solution methodologies before choosing a design approach. • Does not consider a project complete at the first sign of success, but insists on testing and retesting. • Is never content to arrive at a set of design parameters by trial and error. • Use phrases such as “I need to understand why” and “Let’s consider all the possibilities”. A Bad Engineer:

1.5 Good design practices

22

• Equates pure trial and error with engineering design. Green (1992) summarizes skills that seem to mark the expert designer in domains of routine design. Supplying context. The requirements seldom provide enough information to create a design. This occurs in part because the client himself does not know precisely what he/she wants. However, another problem is that the stated requirements imply several other, unstated, requirements. The expert can “read between the lines” and supply context that reduces the search space. Decision ordering. Strategic knowledge is a major part of the designers’ expertise. The expert designer is able to make decisions in the correct order to avoid spending much time in backtracking and revising. Decision ordering is important because it rank constraints. The expert’s decision ordering set constraint values in some optimal sequence. Heuristic classification. Although the overall design problem may be ill-structured, it usually contains some well-structured components. Some decisions fell into the heuristic classification paradigm (here, heuristic means problem-solving techniques that utilize self-education techniques, as the evaluation of feedback, to improve performance). The designer begins by listing requirements, both stated and unstated, and maps them to design parameters which enables him/her to choose a set of design classes. Parameter abstraction. Much of routine design requires to simultaneously manage a large collection of variable values. This can be a very complex cognitive task since it requires the expert to maintain a large amount of information in working memory. Experts are able to reduce the complexity of the problem by abstracting only the most important parameters, treating related parameters as single entities whenever possible.

• Thinks he/she has all the answers; seldom listens to the ideas of others. • Has tunnel vision; pursues with intensity the first approach that comes to mind. • Ships the product out the door without thorough testing. • Use phrases such as “good enough” and “I don’t understand why it won’t works; so-and-so I it this way.” c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

References 1. Cross, N. (1994) Engineering Design Methods, John Wiley & Sons. 2. Eide, A., Jenison, R., Mashaw, L. & Northup, L. (1998) Introduction to Engineering Design. McGraw-Hill. 3. Ertas A. & Jones, J. (1996) The Engineering Design Process, second ed., c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

23

1.5 Good design practices

John Wiley & Sons. 4. Horenstein, M. (1999) Design Concepts for Engineers, Prentice-Hall. 5. Otto, K. & Wood, K. (2001) Product Design - Techniques in Reverse Engineering and New Product Development, Prentice-Hall. 6. Ouyang, S., Fai, J., Wang, Q. & Johnson, K. Quality Function Deployment. University of Calgary Report. 7. Pugh, S. (1990) Total Design, Addison Wesley. 8. Suh, N. (1990) The Principles of Design. Oxford University Press. 9. Ullman, D. (1992) The Mechanical Design Process, McGraw-Hill. 10. Ulrich, K. & Eppinger, S. (2000) Product Design and Development. Irwin McGraw-Hill.

CHAPTER

2

Identifying customer needs

If a new or redesign product is to be successful, it should fulfill the needs of the customer. Unfortunately, the process of finding which are the real needs to be fulfilled is not a straightforward one. According to Ulrich & Eppinger (2000), the goals of a method for comprehensively identifying a set of customer needs should be: 1. Ensure that the product is focused on customer needs. 2. Identify latent or hidden needs as well as explicit needs. 3. Provide a fact base for justifying the product specification. 4. Create an archival record of the needs activity of the development process. 5. Ensure that no critical customer need is missed or forgotten. 6. Develop a common understanding of customer needs among members of the development team. The main purpose of identifying customer needs is to create a direct information link between customers and developers. The involvement of members of the design team (specially engineers and industrial designers) results essential as they must have a clear view of how the product will be used by the end c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e CarlosMiranda. Todos los derechos reservados.

25

2.1 Customer satisfaction

2.1 Customer satisfaction

In this chapter, the next 5 steps to effectively identify customer needs will be discussed:

Customer Satisfaction

user. This direct experience will help the design team not only to discover the true needs of the customer, but also to create better concepts and to evaluate them in a more accurate form.

26 Delighted e urv

eC nc

a rm

rfo

e dP cte

pe Ex

Delighted Performance Curve

Fully Implemented

1. Gather raw data from customers. 2. Interpret the raw data.

Function

Absent

Basic Performance Curve

3. Organize the needs into a hierarchy. 4. Establish the relative importance of the needs. 5. The review of the process and its results.

2.1

Customer satisfaction

In order to satisfy customers, a given product must fulfill customer expectations about it. Even when finding which features are wanted by the customer is a difficult task since customers usually not mention them directly, customer satisfaction translates to the implementation in a given product as much desired features as possible. In order to better understand this relationship, the Kano diagram may be of help. The Kano model shown in figure 2.1, shows the relationship between customer needs and satisfaction in an easy to appreciate diagram ranking the customer satisfaction from disgusted to delighted. 2.1.1. The Kano diagram

The lower curve in Kano’s diagram is called the basic performance curve or expected requirements curve. It represent the essentially basic functions or features that customers normally expect of a product or service. They are usually unvoiced and invisible since successful companies rarely make catastrophic mistakes. However, they become visible when they are unfulfilled.

Disgusted

Figure 2.1: Kano diagram of customer satisfaction. After Otto & Wood (2001).

They satisfy customers when fulfilled. But they do not leave customers dissatisfied when left unfulfilled. And they are invisible to customers since they are not even known. The center line of the Kano diagram is called the one-to-one quality or linear quality line. It represents the minimum expectation of any new product development undertaking. It is related also to performance type issues such as “faster is better.” These represent what most customers talk about. Thus, they are visible to the company and its competitors. The expected requirements and exciting requirements provide the best opportunity for competitive advantage. Hence, ways to make hem visible and then deliver on them are needed.

The upper curve in Kano’s diagram is called the delighted performance curve or exciting requirements curve. They are a sort of “out of the ordinary” functions or features of a product or service that cause “wow” reactions in customers.

Kano’s diagram is often interpreted simply as a relationship model of expected quality vs. excited quality. What is really important, however, is that the target of customer satisfaction can not only invisible but also moving. Customer expectations increase over time. This calls for a more complex analysis and deeper market understanding.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

27

2.1 Customer satisfaction

2.2 Gather data from customers

28

According to Otto & Wood (2001) customer needs may be profitably considered in general categories based on how easy the customer can express them and how rapidly they change. They can be classified in three categories: first, direct and latent needs which consider observability, second, constant and variable needs which consider technological changes and finally, general and niche needs which consider variance in the consumers.

2.2

Direct needs These are the needs that, when asked about the product customer have no trouble declaring as something they are concerned about. These are easily uncovered using standard methods as the one that will be described hereafter.

Interviews One or more members of the design team interview a number of customers, one at a time. Interviews are generally carried out in the environment of the costumer where the product is used. They typically last for one to two hours.

Latent needs These are the needs that typically are not directly expressed by the customer without probing. Customer typically do not think in modes that allow themselves to express these needs directly. Latent needs are better characterized as customer needs, not of the product, but of the system within which the product operates. Other products, services or actions currently satisfy the needs directly. Yet, these needs might be fulfilled with a developing product, and doing so can provide competitive advantage.

Questionnaires A list of important concerns, questions and criteria is prepared by the design team and sent to selected customers. Although this type of survey is quite useful at later stages of the design process, at this stage they do not provide enough information about the use environment of the product. It is also important to notice that not all needs may be revealed using this method.

2.1.2. Types of customer needs

Constant needs These needs are intrinsic to the task of the product and always will be. When a product is used, this need will always be there. Such needs are effective to examine with customer needs analysis, since the cost can be spread over time. Variable needs These needs are not necessarily constant; if a foreseeable technological change can happen, these needs go away. These needs are more difficult to understand through discussions with the customer, since the customer may not understand them yet. General needs These needs apply to every person in the customer population. It is necessary for a product to fulfill these needs if it is to compete in the existing market. Niche needs These needs apply only to a smaller market segment within the entire buying population.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Gather data from customers

In order to obtain information from customers, several methods are available: interviews, questionnaires, focus groups, observing the product in use and finally, be the customer oneself. In what follows, a brief description of each one together with pros and cons is given.

Focus groups A group of 8 to 12 customers participate in a discussion session facilitated by a moderator. Focus groups are typically conducted in a special room equipped with a two-way mirror allowing several members of the development team to observe the group. It is desired for the moderator to be a professional market researcher, but a member of the development team can also perform as moderator. Observing the product in use When watching a customer using an existing product or perform a task for which a new product is intended, details about customer needs can be reveled. Observation may be passive, leaving the customer to use the product without any direct interference or can be carried out along with one of the design team members allowing the development of firsthand experience about the use of the product. Be the customer In many situations, members of the design team may perform as users of existing competitor products or, in later stages of the design process, of prototypes. Although this method is very cost effective and relatively easy to perform as no persons outside the design team are involved, it posses two main problems. First, members of the design team may not have the required skills or experience to accurately evaluate the product, and second, they may feel biased towards certain characteristics of the product. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

29

2.2 Gather data from customers

Lead Users

Users

Retailer or Sales Outlet

Service Centers

Occasional User Frequent User Heavy−duty User

Figure 2.2: Customer selection matrix. After Ulrich & Eppinger (2000).

2.2 Gather data from customers

30

Ulrich and Eppinger provide some general hints for effective customer interaction. First, they suggest to sketch an interview guide that help to obtain an honest expression of needs. This can not be stressed enough, the goal of the interview is to obtain customer needs, not to convince the customer of what he or she really wants. Some helpful questions and prompts to use are: 2.2.2. Conducting Interviews

• When and why do you use this type of product? • Walk us through a typical session using the product. • What do you like about the existing products? • What do you dislike about the existing products?

From the above methods, research carried out by Griffin and Hauser (1993) reports that conducting interviews is the most cost and effort effective method. According to their report, one 2-hour focus group reveals about the same number of needs as two 1-hour interviews. They also report that interviewing nine customers for one hour each will obtain over 90% of the customer needs that would be uncovered when interviewing 60 customers. These figures where obtained when a single function product was being considered, and may change when considering multi-function products. According to Ulrich & Eppinger, as a practical guideline for most products, conducting fewer than 10 interviews is probably inadequate and 50 interviews are probably too many.

Selecting customers is not always a straightforward activity as many different persons may be considered a “customer”. Consider, for example, all those products that are purchased by one person and used by another. In all cases, it is important to gather information from the end user, and then gather information from other type of customers and stake-holders. 2.2.1. Selecting customers

A customer selection matrix like the one shown in figure 2.2, is useful for planning exploration of both market and customer variety. It is recommended that market segments be listed on the left side of the matrix while the different types of customers are listed across the top. The number of intended customer contacts is entered in each cell to indicate the depth of coverage.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

• What issues do you consider when purchasing the product? • What improvements would you make to the product? Second, they suggest the following general hints for effective interaction with customers: • Go with the flow. If the customer is providing useful information, do not worry about conforming to the interview guide. The goal is to gather information data on customer needs, not to complete the interview guide in the allotted time. • Use visual stimuli and props. Bring a collection of existing and competitors’ products, or even products that are tangentially related to the product under development. At the end of a session, the interviewers might even show some preliminary product concepts to get customers’ early reactions to various approaches. • Suppress preconceived hypotheses about the product technology. Frequently customers will make assumptions about the product concept they expect would meet their needs. In these situations, the interviewers should avoid biasing the discussion with assumptions about how the product will eventually be designed or produced. When customers mention specific technologies or product features, the interviewer should probe for the underlying need the customer believes the suggested solution would satisfy. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

31

2.2 Gather data from customers • Have the customer demonstrate the product and/or typical tasks related to the product. If the interview is conducted in the use environment, a demonstration is usually convenient and invariably reveals new information.

2.2 Gather data from customers Customer Data: Project/Product Name Customer: Address: Willing to do follow up? Type of user: Question

Customer Statement

32

Interviewer(s): Date: Currently uses: Interpreted Need

Importance

• Be alert for surprises and the expression of latent needs. If a customer mentions something surprising, pursue the lead with follow-up questions. Frequently, an unexpected line of questioning will reveal latent needs important dimensions of the customers’ needs that are neither fulfilled nor commonly articulated and understood. • Watch for nonverbal information. The design process is usually aimed at developing better physical products. Unfortunately, words are not always the best way to communicate needs related to the physical word. This is particularly true of needs involving the human dimensions of the product, such as comfort, image or style. The development team must be constantly aware of the nonverbal messages provided by customers. What are their facial expressions? How do they hold competitors’ products? 2.2.3. How to document interactions

There are four main methods for documenting interactions with customers:

Notes Handwriting notes are the most common method of documenting an interview. If a person is designated as notetaker, other person can concentrate in effectively questioning the customer. The notetaker should try to capture the answers of the customer in a verbatim form. If the notes from the interview are transcribed inmediately after it, a very close account of the interview can be obtained.

Figure 2.3: Customer data template. After Otto & Wood (2001).

the advantage of being inexpensive and easy to do. One useful aid in the collection of data from a customer interview is a customer data template. A customer data template, like the one shown in figure 2.3, helps to record questions, answers and comments. The template can be filled during the interview or inmediately afterwards.

Video recording Video recording is the usual way of documenting focus group sessions. It is also very useful for documenting observations of the customer in the use environment and the performance of existing products.

In the first column, the question prompted is recorded. In the second column, a verbatim description of the answer and comments given by the customer is recorded. In the third column, the customer needs implied by the raw data are written. Special attention must be given to clues that may identify potential latent needs like humorous remarks, frustrations or non-verbal information. In the last column, linguistic expressions of importance that the customer may have used are recorded. The importance may be expressed in terms of words like must, good, should, nice or poor.

Still photography Even when dynamic information cannot be captured by it, still photography can be used to capture high quality images. It also has

According to Otto & Wood, a must is used when a customer absolutely must have this feature, generally when it is a determining criterion in purchasing

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Audio recording Audio recording is probably the easiest way of documenting and interview. Unfortunately, many customers feel intimidated by it. Another disadvantage is that transcribing the recording into text is very time consuming.

33

2.3 Interpret raw data

the product. Must ratings should be used very sparingly; only a few must’s per customer interview is a good rule. A very important customer need should have a good importance rating. Needs that are presumed should have at least a should rating. If the customer feels the product should satisfy this requirement, it is important enough for the design team to consider it. The nice category is for customer needs that would be nice if the product satisfied them but are not critical.

2.3

2.4 Organization of needs

Guideline

Customer Statement

Need Statement - Right

Need Statement - Wrong

“What” not “how”

“Why don’t you put protective shields around the battery contacts?”

The screwdriver battery is protected from accidental shorting.

The screwdriver battery contacts are covered by a plastic sliding door.

Specificity

“I drop my screwdriver all the time.”

The screwdriver operates normally after repeated dropping.

The screwdriver is rugged.

Positive not negative

“It doesn’t matter if it’s raining; I still need to work outside on Saturdays.”

The screwdriver operates normally in the rain.

The screwdriver is not disabled by the rain.

An attribute of the product

“I’d like to charge my battery from my cigarette lighter.”

The screwdriver battery can be charged from an automobile cigarette lighter.

An automobile cigarette lighter adapter can charge

Avoid “must” and “should”

“I hate it when I don’t know how much juice is left in the batteries of my cordless tools.”

The screwdriver provides an indication of the energy level of the battery.

The screwdriver should provide an indication of the energy level of the battery.

Interpret raw data

At this point, customer needs are expressed in terms of verbatim written statements. Every customer comment or observation as expressed in the customer data template may be translated into any number of customer needs. It has been found that multiple analysts may translate the same interview notes into different needs, so it is convenient for more than one team member to be involved in this task.

34

Table 2.1: Examples illustrating the guidelines for writing need statements for a cordless screwdriver (After Ulrich & Eppinger, 2000). • Express the need as an attribute of the product. Wording needs as statements about the product ensure consistency and facilitates subsequent translation into product specifications.

Ulrich & Eppinger provide five guidelines for writing need statements. They recognize the first two as fundamental and critical to effective translation, and the remaining three as guidelines to ensure consistency of phrasing and style across all team members. Table 2.1 shows examples to illustrate each guideline.

• Avoid the words must and should. The words must and should imply a level of importance for the need.

• Express the need in terms of what the product has to do, not in terms of how it might do it. Customers often express their preferences by describing a solution concept or an implementation approach; however, the need statement should be expressed in terms independent of a particular technological solution.

After all the customer comments have been translated into need statements, the design team ends up with a group of maybe tens or even hundreds of need statements. At this point, some may be similar, other may not be technological feasible, and others may express conflicting needs. In the following section, methods for organizing and classifying these needs are presented.

• Express the need as specifically as the raw data. Needs can be expressed at many different levels of detail. To avoid loss of information, express the need at the same level of detail as the raw data.

2.4

• Use positive, not negative, phrasing. Subsequent translation of a need into a product specification is easier if the need is expressed as a positive statement. This may not apply in those occasions when the statement is expressed more naturally in negative terms. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Organization of needs

2.4.1. Classification of needs

In order to work effectively with all the customer needs, it is necessary to classify them in groups of equal or similar statements. Each group may be subsequently sorted out in a list according to the relative

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

35

2.4 Organization of needs

2.5 Design brief

36

importance of each need in the group. Each group list typically consists of a set of primary needs, each one of which will be characterized by a set of secondary needs and if needed, tertiary needs.

Importance

This process of sorting and classification is normally performed by the design team. Nevertheless, it also exists the possibility of leaving this task to a group of selected customers. According to Otto and Wood, this approach prevents the customer data from being biased by the development team. The classification of needs can be done without many difficulties following the next steps:

Ranking 1

Ranking 2

Must

9

1.0

Good

7

0.7

Should

5

0.5

Nice

3

0.3

not mentioned

0

0

Table 2.2: Two different ranking systems for the importance of needs. interpreted importance rank of the ith customer need can be obtained from

1. Write each need on a small card.

Ri =

2. Group similar needs eliminating redundant statements. 3. Choose a descriptive name for each group. 4. Review the process and consider alternative ways of grouping the statements. When working with different customer segments, cards with different color labels can be used to distinguish between them. The sorting and classification process can also be done separately for each customer segment observing differences in both the needs themselves and their organization. The latter approach is best suited when the segments are very different in their needs and when there is the question if just one product may suit the needs of all segments. As of now, the classification of needs does not provide any information regarding the relative importance that the customer place on different needs. Each customer need has an importance expressed by the own customer during the interview. It is expected that different customers will feel different regarding the importance of features according to their own use of the product.

2.4.2. Determination of relative importance of needs

number of times mentioned number of subjects

(2.1)

It is important to have in mind that the above method may raise inconclusive results as it mainly measures the obviousness of the need as opposed to its importance. Therefore, needs that may be obvious but not important may be ranked high as opposed to important needs that may not be obvious. A more correct approach, is to include in the ranking the importance statements given by the customer during the interview. In order to do so, it is necessary to convert the subjective importance ratings into numerical equivalents. A typical transformation is shown in table 2.2. Once the mapping has been carried out, the importance assigned to each customer need can be calculated as: average rating × number of times mentioned Ri = (2.2) number of subjects Although a better method of ranking customer needs, the previous method has also its own flaws as it still may hide important needs that were reveled by only few customers but were not seen by the rest.

2.5

Design brief

An elementary approach to establish the relative importance of needs is to first construct a set of normalized weightings by comparing the number of subjects who mention a need versus the total number of subjects. Hence, the

After grouping and ranking customer needs, a better idea of the design problem is at hand. To keep a clear idea of the direction of the design process, the design

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

37

2.6 Clarifying customer needs

team may issue what is called a design brief or mission statement. A design statement includes a brief description of the product, key business goals, target markets, assumptions and constraints and stakeholders:

• Description of the product A brief description typically includes the key customer benefits of the product avoiding implying a specific product concept. • Key business goals. These goals generally include goals for time, cost, quality and market share. Other goals may be added as deem appropriate. • Target markets. Identifies the primary as well as secondary markets that should be considered during the design process. • Assumptions and constraints. In some projects is necessary to make assumptions in order to keep a project of manageable scope and size. In other occasions, time, cost or even feature constraints are known from the beginning of the product. • Stakeholders. It is always convenient to list all the stakeholders in order to handle subtle issues that may appear during the development process. Stakeholders are all the groups of people who are affected by the success or failure of the product. The list usually begins with the end user and the customer who makes the buying decision about the product. Stakeholders also include the customers residing within the firm such as the sales force, the service organization and the production departments.

2.6

Clarifying customer needs

One step further in the determination of customer needs is to try to clarify all the customer need that were grouped, classified and prioritized. In fact, it is very helpful to have the clearest possible idea of the customer needs at all stages of the design process. These customer needs, that will guide the design process, should be expressed in a form which is easily understood and which can be agreed by both, client and designer. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

2.6 Clarifying customer needs

38

2.6.1. The objectives tree The objectives tree method offers a clear and usemethod ful format for such a clarification of customer need statements in form of objectives. It also shows in a diagrammatic form the ways in which different objectives are related to each other and the hierarchical pattern in which they are organized. As with many methods in the design process, the objectives tree is not as important as the procedure for arriving at it. One way to start making vague statements more specific is to try to simple specify what it means. Consider the following example provided by Cross (1994) where an objective for a machine tool must be ‘safe’. This objective might be expanded to mean: 1. Low risk of injury to operator. 2. Low risk of operator mistakes. 3. Low risk of damage to work-piece or tool 4. Automatic cut-out on overload. These different statements can be generated simply at random as the design team discusses about the objective. The types of questions that are useful in expanding and clarifying objectives are simple ones like ‘why do we want to achieve this objective?’ and ‘what is the problem really about?’. Some authors also include questions like ‘How can we achieve it?’ starting to give some insight about how the objectives may be accomplished. This gives way to statements like ‘automatic cut-out on overload’ which are not objectives by themselves but means of achieving certain objectives. Nevertheless, it is difficult to avoid making concessions reducing the scope of the possible solutions that may be generated in later stages of the design process. For this reason, in the approach followed here, everything related to the ‘how to’ accomplish objectives will be left to the concept generation stage. As the list of objectives is expanded, it becomes clear that some are at higher levels of importance than others. This relative importance may be represented in a hierarchical diagram of relationships as shown in figure 2.4. In some cases, the relative position of each statement in the diagram may be a source of disagreement between the different members of the design team. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

39

2.6 Clarifying customer needs

2.6 Clarifying customer needs

40

Machine must be safe

Provide opening

How Low risk of injury to operator

Low risk of operator mistakes

Low risk of damage to workpiece or tool

Enable in/out

Pivot door Open door

Why

Push/pull door

Automatic cut−out on overload

Close door

Figure 2.4: Hierarchical diagram of relationships. After Cross (1994).

Keep weather out Povide seal

However, exact precision of relative levels is not important, and most people can agree when only a few levels are being considered. At this point, it is important to notice that the level of importance of the statement should not be confused with the level of importance of the customer need. Here, importance is related to the statements written to try to clarify one objective, which correspond to one customer need.

When open

Provide protection

Correct amount

Safe force

In many cases, different people will draw different objectives trees for the same problem or the same set of objective statements. The tree diagram simply represents one perception of the problem structure. It is only a temporary representation, which will probably change as the design process proceeds. One more elaborated example of an objective tree is shown in figure 2.5 where the objectives tree for the design of a car door is shown.

Safe direction

Against injury

When closing

Resist impact Resist damage

Provide safety

Safe interior

When closed

The procedure of building an objectives tree can be summarized using the following steps:

Strong latch

Provides latch Latches securely

Against theft

Secure handle Inaccessible lock

Figure 2.5: Objectives tree for a car door. After Pugh (1991).

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

41

2.6 Clarifying customer needs

2.6 Clarifying customer needs

42

1. Prepare a list of design objectives. Black Box

2. Order the list into sets of higher-level and lower-level objectives. 3. The expanded list of objectives and sub-objectives is grouped roughly into hierarchical levels.

Inputs

Transparent Box

From the objectives tree method, it is clear that design problems can have different levels of generality or detail. Hence, the level at which the problem is defined is crucial and it is always appropriate to question the level at which the design problem is posed. On the other hand, focusing too narrowly on a certain level may hide a more radical or innovative solution.

2.6.2. The functional decomposition method

The function decomposition method offers such means of considering essential functions and the level at which the problem is to be addressed. The essential functions are those that the device, product or system to be design must satisfy, independently what physical components might be used to fulfill them.

Outputs

Figure 2.6: A ‘black box’ system model. After Cross (1994).

4. Draw a diagrammatic tree of objectives showing hierarchical relationships which suggest means of achieving objectives.

In any way, it is useful to have means of considering the problem level at which a design team is to work. It is also very useful if this can be done considering the essential functions that a solution will be required to satisfy. This approach leaves the design team free to develop alternative solution proposals that satisfy the functional requirements.

Function

Subfunction

Subfunction

Inputs

Subfunction

Subfunction

Function

Outputs

Figure 2.7: A ‘transparent box’ model. After Cross (1994). are the outputs for?, what is the next stage of conversion?, etc. can be made to the customer. Usually the conversion of the set of inputs into the set of outputs is a complex set of tasks occurring inside the black box. This complex set of tasks must be broken down into sub-tasks or sub-functions which linked together by their inputs and outputs satisfy the overall function of the product or device being designed. As this necessary sub-functions are establish, the black box is redraw as a ‘transparent box ’ (see figure 2.7).

The starting point of this method is to clarify what is the main purpose of the design. As it has been up to now, it is important what has to be achieved by the new design and not how is going to be achieved. The most simple way of representing this main purpose is to draw a ‘black box ’ which converts certain inputs into desired outputs (see figure 2.6). This black box contains all the functions which are necessary for converting inputs into outputs.

According to Pahl and Beitz (2001), anyone setting up a function structure ought to bear the following points in mind:

At this point, it is preferable to try to make this overall function as broad as possible, avoiding to start with a narrow function that limits the range of possible solutions. In order to establish in an accurately way the required inputs and outputs as well as the ‘system boundary’ which defines the function of the product or device, questions like where do the inputs come from?, what

1. First derive a rough function structure with a few sub-functions from what functional relationships you can identify in the requirements list, and then break this rough structure down, step by step, by the solution of complex sub-functions. This is much simpler than starting out with

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c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

43

2.6 Clarifying customer needs more complicated structures. In certain circumstances, it may be helpful to substitute a first solution idea for the rough structure and then, by analysis of that first idea, to derive other important sub-functions. It is also possible to begin with subfunctions whose inputs and outputs cross the assumed system boundary. From these it is possible to determine the inputs and outputs for the neighboring functions, in other words, work from the system boundary inwards.

2.6 Clarifying customer needs • Storing energy – for instance, storing kinetic energy. Conversion of material: • Changing matter – for instance, liquefying a gas. • Varying material dimensions – for instance, rolling sheet metal. • Connecting matter with energy – for instance, moving parts.

2. If no clear relationship between the sub-functions can be identified, the search for a first solution principle may, under certain circumstances, be based on the mere enumeration of important sub-functions without logical or physical relationships, but if possible, arranged according to the extent to which they have been realized.

• Connecting matter with signal – for instance, cutting off steam.

3. Logical relationships may lead to function structures through which the logical elements of various working principles (mechanical, electrical, etc.) can be anticipated.

• Storing material - for instance, keeping grain in a silo.

4. Function structures are not complete unless the existing or expected flow of energy, material and signals can be specified. Nevertheless, it is useful to begin by focusing attention on the main flow because, as a rule, it determines the design and is more easily derived from the requirements. The auxiliary flows then help in the further elaboration of the design, in coping with faults, and in dealing with problems of power transmission, control, etc. The complete function structure, comprising all flows and their relationships, can be obtained by iteration, that is, by looking first for the structure of the main flow, completing that structure by taking the auxiliary flows into account, and then establishing the overall structure. 5. In setting up function structures it is helpful to know that, in the conversion of energy, material and signals, several sub-functions recur in most structures and should therefore be introduced first. Essentially, the generally valid functions are described next. Conversion of energy:

44

• Connecting materials of different type – for instance, mixing or separating materials. • Channelling material - for instance, mining coal.

Conversion of signals: • Changing signals – for instance, changing a mechanical into an electrical signal, or a continuous into an intermittent signal. • Varying signal magnitudes – for instance, increasing a signal’s amplitude. • Connecting signals with energy – for instance, amplifying measurements. • Connecting signals with matter – for instance, marking materials. • Connecting signals with signals – for instance, comparing target values with actual values. • Channelling signals – for instance, transferring data. • Storing signals – for instance, in data banks. 6. In the case of mechanical devices, table 2.3 can be a good starting point to identify functions.

• Changing energy – for instance, electrical into mechanical energy. • Varying energy components – for instance, amplifying torque. • Connecting energy with a signal – for instance, switching on electrical energy. • Channeling energy – for instance, transferring power. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

7. For the application of micro-electronics, it is useful to consider signal flows as shown in figure 2.5. This results in a function structure that suggests clearly the modular use of elements to detect (sensors), to activate (actuators), to operate (controllers), to indicate (displays) and, in particular, to process signals using microprocessors. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

45

2.6 Clarifying customer needs

Operate

User

Indicate

Process (control)

Detect

Technical system

Activate

Figure 2.8: Basic signal flow functions for modular use in micro-electronics. After Pahl and Beitz (2001). 8. From a rough structure, or from a function structure obtained by the analysis of known systems, it is possible to derive further variants and hence to optimize the solution, by: • braking down or combining individual sub-functions; • changing the arrangement of individual sub-functions; • changing the type of switching used (series switching, parallel switching or bridge switching); and • shifting in the system boundary. Because varying the function structure introduces distinct solutions, the setting up of function structures constitutes a first step in the search for solutions. 9. Function structures should be kept as simple as possible, so as to lead to simple and economical solutions. To this end, it is also advisable to aim at the combination of functions for the purpose of obtaining integrated function carriers. There are, however, some problems in which discrete functions must be assigned to discrete function carriers, for instance, when the requirements demand separation, or when there is a need for extreme loading and quality.

2.6 Clarifying customer needs

46

Absorb/remove

Dissipate

Release

Actuate

Drive

Rectify

Amplify

Hold or fasten

Rotate

Assemble/disassemble Increase/decrease

Secure

Change

Interrupt

Shield

Channel or guide

Join/separate

Start/stop

Clear or avoid

Lift

Steer

Collect

Limit

Store

Conduct

Locate

Supply

Control

Move

Support

Convert

Orient

Transform

Couple/interrupt

Position

Translate

Direct

Protect

Verify

Table 2.3: Typical mechanical design functions. After Ullman (2003). The procedure to follow to establish the required functions and the system boundary of a new design can be stated using the following steps: 1. Express the overall function for the design in terms of the conversion of inputs and outputs. 2. Break down the overall function into a set of essential subfunctions. 3. Draw a block diagram showing the interaction between subfunctions. 4. Draw the system boundary. The system boundary defines the functional limits for the product or device to be designed. In order to effectively apply the functional decomposition method, the following guidelines should be followed: 1. Document what not how. 2. Use standard notation when possible. 3. Consider logical flows.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

47

2.6 Clarifying customer needs Cold water

2.6 Clarifying customer needs

48

Hot tea

(measured quantity) Tea begin BREWED Tea leaves (measured quantity)

Tea leaves (waste)

Figure 2.9: Black box model of the tea brewing process. After Cross (1994). 4. Match inputs and outputs in the functional decomposition. (a)

Water

5. Break the function down as finely as possible. One simple example that can be used to illustrate the process of functional decomposition is that of a tea maker (Cross, 1994). The fundamental process to be achieved by such a machine is to convert cold water and tea leaves into hot tea as illustrated in figure 2.9.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Tea is infusing

Tea and water are separated

Tea leaves

(b)

Water

Leaves

Tea Water is heated

Tea leaves are immersed

Energy Tea leaves

(c)

1. Cross, N. (1994) Engineering Design Methods, John Wiley & Sons. 2. Otto, K. & Wood, K. (2001) Product Design - Techniques in Reverse Engineering and New Product Development, Prentice-Hall. 3. Pahl, G. and Beitz W. (2001) Engineering Design - A systematic Approach. Second Ed. Springer. 4. Ullman, D. (2003) The Mechanical Design Process. Third Ed. McGraw-Hill. 5. Ulrich, K. & Eppinger, S. (2000) Product Design and Development. Second Ed. Irwin McGraw-Hill.

Water and tea united

Energy

Some transparent box models of the tea maker are shown in figure 2.10. These models represent three alternative processes by which the overall function can be achieved. After considering them, the designer settled on the first process where various necessary auxiliary functions became apparent, specially regarding the control of the heating and brewing processes.

References

Tea Water is heated

Water Water is heated

Tea leaves are wetted

Leaves

Concentrate and water are united

Tea

Energy

Figure 2.10: Three alternatives to the transparent box model for the tea brewing process. After Cross (1994).

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

3.1 Benchmarking

50

they understand their product by mere self-inspection, they are closing doors to a wide array of alternative possibilities.

CHAPTER

3

Benchmarking and Product Specifications

Benchmarking the competition as an activity in the product development process overlaps many of the other activities as it generates data that is important to understand a product and forecast its future development. This activity cannot be understated, product developers must learn from competitors. Companies must avoid the Not-Invented-Here (NIH) syndrome that presents when engineers at a company choose not to use technology developed outside it as it is considered to not be of any good. This may cause a product to fail, as it leaves the design teams and companies behind as new technology emerges at the marketplace. Design teams must understand the importance of newly introduced technology by competitors and be ready to respond. Benchmarking allows to meet this goal. It is also an important step in establishing engineering specifications.

3.1

Benchmarking

A famous example of understanding the competition is that of Xerox Corporation. When in 1979 Xerox marketshare in the copy machines segment was rapidly decreasing, its engineers pondered the following question: “How in the world could the Japanese manufacture in Japan, ship it over to the United States, land it, sell it to a distributor who sells it to a dealer who marks up the cost to the final customer, and the price the customer pays is about what it would cost us to build the machine in the first place?” (Jacobson and Hillkirk, 1986). Even when at the time Xerox was not able to analyze and understand competitor’s product, production and distribution, they have now competitive benchmarking activities. These activities allows them to focus on how to be successful, rather than how competitors can be better than them. In order to understand the competition, design teams must tear down and analyze competitive products. This activity must be done periodically, not only supporting new design efforts but also developing a continuous understanding of trends and directions in technology development. Many large companies have entire departments devoted only to benchmarking activities. These departments provide insight not only on new technological developments, but also in the position of the company’s products in the marketplace in terms of quality, value and performance. Benchmarking activities are vital at all stages of the product development as they: • provide a way to understand what needs other products are satisfying • provide means to establish product specifications ensuring that products goals superpass existing competition • help in the concept generation stage providing best-in-class concepts • help to incorporate in the detailed design new and improved design features of the best-in-class products

There are two main purposes for studying existing competitive products: first, creates an awareness of what products are already available, and second, reveal opportunities to improve what already exists. Design teams must be aware not only on what other products offer, but also how other competitors provide similar products. As Otto & Wood (2001) clearly state, when engineers think

According to Otto & Wood (2001), product benchmarking can be carried out following the next steps:

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c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

• help to find the best-in-class components and suppliers

51

3.1 Benchmarking 1. Form a list of design issues 2. Form a list of competitive or related products 3. Conduct an information search 4. Tear down multiple products in class 5. Benchmark by function 6. Establish best-in-class competitors by function 7. Plot industry trends

A list of issues must be developed for comparative benchmarking. Further, this list should be continually revised and updated. With a focus for benchmarking efforts, an efficient exploration path may be pursued. The result is a reduction in wasted time and resources.

3.1.1. Form a list of design issues

Considering the design issues and product function in product development, the next step is to examine retailer stores and sales outlets for products that demonstrate these issues. For a product, it is necessary to list all competitors and their different product models. In addition, all related products in their portfolio should be listed. If the competitors have a family of products under a common platform (they use identical components for some aspects of each product but different components for niche demands), detailed information about this should be included as it indicate the competitor’s preferred market segments and compromises made for other market segments. 3.1.2. Form a list of competitive or related products

3.1 Benchmarking

52

3.1.3. Conduct an The information search is a step of great importance. In information search order to benchmark a piece of hardware, the design team must gather as much information about the product as possible. Any printed article that mentions the product, its features, its materials, the company, manufacturing locations or problems, customers, market reception or share, or any other information will be useful. Because of the proliferation of computerized databases and the World Wide Web, a good library is essential. There is a generous amount of information available about all business operations. Before starting any design activity, a team must understand the market demand for product features and what the competition is doing to meet it. A design team should gather information on • the products and related products • the functions they perform • the targeted market segments All keywords associated with these three categories should be formed and used in informational searches. Sources of information can be quite varied. Most businesspersons are perfectly happy to discuss the market and noncompetitive business units. Although most businesspersons will not provide strategic information about their own companies, many people are happy to tell all about their competitors. Suppliers will usually discuss their customers as they can, if it appears that the requester might provide an additional sale. The key is always to be open, honest and ethical when questioning for information. Once people understand that a design team is designing a new product or redesigning an existing one, they naturally want to get involved with new orders and will help the team as far as they legally can. Pursuit of information beyond that point is unethical and not necessary. Most people are happy to share information, and so simple honesty and a friendly attitude can get team members along way.

This step should only be an identification of the competitors in the form of company names and product names. With a complete set of different products, vendors and suppliers to examine, the list should be screened by highlighting the particular competitors that appear most crucial for the design team to fully understand. This step serves as basis for the next step, conducting an information search.

Sources of information can be divided in two main groups: public sources that are freely accessible, and market research databases that are accessible through a fee.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Public sources of product information include:

53

3.1 Benchmarking

Libraries University libraries are filled with technical engineering modeling references. Many libraries that does not have a large book count, have access to other larger libraries where information may be found and retrieved through inter-library loans. Thomas Register of Companies This set of documents is a “yellow pages” for manufacturing-related business. The Thomas Register list vendor by product name (http://www.thomasregister.com). Consumer Reports Magazines These magazines survey and test a number of common consumer products. Useful data are available for customer needs, qualitative benchmarking, engineering specifications, and warranty andmaintenance information. If a given product is not covered in the magazines, other products can provide analogies as a starting point. (http://www.consumerreports.com/, http://www.profeco.gob.mx/new/html/revista.htm). Trade Magazines Consumer trade magazines such as Car and driver, Byte, Consumer Electronics, JD Powers and Associates, and others provide comparative studies of products within a field. Such studies are very useful to understand how a given product compares with the competition and to understand important customer and technical criteria. Patents After examining trade journals and uncovering which competitors have new innovations, gathering the patents on these new innovations explains much. Patent searches based on company names are difficult since companies typically “bury” their patents by filing them under the individual names of designers. Uncovering the individual patents is usually through refined topical searches, and hence, as much information as possible should be at hand when doing the research. Patent information may be obtained from the Classification and Search Support System (CASSIS) of from Web sites such as http://www.patents.ibm.com/. Market Share Reporter Published every year by International Thomson Publishers, this book summarizes the previous market research of Gale Research, Inc. It is composed of market research reports from the periodicals literature. It includes corporate market shares, institutional shares and brand market shares. National Bureau of Standards This U.S. government branch provides, among other things, national labor rates for all major countries. This inforc Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

3.2 Setting product specification

54

mation proves very useful for determining competitors manufacturing costs. Census of Manufactures Taken every 5 years by the U.S. Department of Commerce, this census includes statistics on employment, payroll, inventories, capital expenditures, and selected manufacturing costs. Also, the supplemental Current Industrial Reports lists production and shipment data on industries and some products. Moody’s Industry Review Taken every 6 months, this survey provides key financial information, operating data, and ratios on about 3,500 companies. Companies as an industry group may be compared with one another group and against industry average. Even when benchmarking can help to understand the market, forecast trends and identify key innovations and technology, one complaint about it is that always provide lagging information. Hence, it is argued that market leaders can find little or no information at all through this practice. 3.1.4. Some comments about benchmarking

Nevertheless, it should be realized that very few market leaders constantly produce leading technology in a market. Markets are always evolving and the opportunity for a competitor to produce new exciting technology is always latent. One way market leaders can benefit from benchmarking is from focusing it on components rather than in products. Components benchmarking may allow them to introduce new technology in components that are not directly developed by them. One problem is commonly associated with benchmarking is the “chasing the competition” syndrome. This problem presents when benchmarking is only used to see what the competition is doing rather than to help the development of new competitive products.

3.2

Setting product specification

After benchmarking, one next step is to use the information gathered up to this point to set targets for a new product development effort. Specifications for a new product are quantitative, measurable criteria that the product should be designed to satisfy. In order to be useful, each specification should consist of a c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

55

3.2 Setting product specification

metric and a value. This value can be a specific number or a range. Examples are: 50 Hz, 30-40 N, > 10 dB, etc. In general terms, specifications fall into two categories, functional requirements and constraints. As discussed before, functional requirements or engineering design specifications are statements of the specific performance of a design, what the device should do. On the other hand, constraints are external factors that limit the selection of the characteristics of the system or subsystem. Constraints are not directly related to the function of the system, but apply across the set of functions for the system. In many situations, constraints can drive the design process of a product and should be established only after critical evaluation. Setting specifications is generally not a straightforward task, and specifications are usually checked several times during the design process. Several concepts may be derived from a customer requirement giving rise to different engineering specifications. Take for example a lid that can be either screwed or pushed to close a container. Both solutions will give way to different engineering specifications since in the first case to screw is related to torque and in the second one to push is related to force. In this case, early concept-independent criteria such as “opening ease” may be refined later into performance specifications for the selected concept. In those specifications that are not expected to change during the design process, margins in target values of ±30% at the beginning of the design process are commonly expected. In any case, it is primordial for each specification should be measurable, and testing and verification of it should be possible at any stage. If for any reason, a specification is not testable and quantifiable, it is not a specification. Ulrich and Eppinger (2000) suggest to consider a few guidelines when constructing the list of specifications: • Specifications should be complete. Ideally each customer need would correspond to a single specification, and the value of that specification would correlate perfectly with satisfaction of that need. In practice, several specifications may be necessary to completely reflect a single customer need. • Specifications should be dependent, not independent, variables. As do customer needs, specifications also indicate what the product must do, not how the specifications will be achieved. Designers use many types c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

3.2 Setting product specification

56

of variables in product development; some are dependent, such the mass of a product and other are independent, such as the material used to manufacture the product. In other words, designers cannot control mass directly because it arises from other independent decisions the designer will make, such as dimensions and material choices. Metrics specify the overall performance of a product and should therefore be the dependent variables in the design problem. By using dependent variables for the specifications, designers are left with the freedom to achieve the specifications using the best approach possible. • Specifications should be practical. It does not serve the team to devise a specification for a given product that can only be measured by a scientific laboratory at a cost of several thousand dollars. Ideally, specifications will be directly observable or analyzable properties of the product that can be easily evaluated by the team. • Some needs cannot easily be translated into quantifiable specifications. Needs like “the product instills pride” may be critical to success, but are difficult to quantify. In this cases the team simply repeats the need statement as a specification and notes that the metric is subjective and would be evaluated by a panel of customers. • The specifications should include the popular criteria for comparison in the marketplace. Many customers in various markets buy products based on independently published evaluations (see examples of sources in the previous section). If the team knows that its product will be evaluated by the trade media and knows what the evaluation criteria will be, then it should include specifications corresponding to these criteria. 3.2.1. Specification Lists With the above guidelines, a specification list like the ones shown in tables 3.1 and 3.2 can be generated. In order to help with the search for relevant design specifications, an approach known as Specification List Generation can be of some help. Specification List Generation uses the decomposition method to obtain a list of general specifications from latent needs such as safety, regulations and environmental factors. Each specification can be labeled as a required demand or a desirable wish to communicate its level of importance. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

57

3.2 Setting product specification

3.2 Setting product specification

58

To identify specifications, the table 3.3 devised by Franke (1995) provides a good starting point. In order to apply Franke approach follow the next steps: 1. Compile specifications and constraints and label them accordingly. Start with specifications and follow with constraints. 2. Determine if each of the functional requirements and constraints is a demand or wish. 3. Determine if each of the functional requirements and constraints are logically consistent. Check for obvious conflicts. Check that specifications are technically and economically feasible. 4. Quantify wherever possible. 5. Determine detailed approaches for ultimately testing and verifying the specifications during the product development process. 6. Circulate specifications for comment and/or amendment inside and outside the development team. 7. Evaluate comments and amendments. Up to this point, several pieces of information are available to the design team. Without proper guidance, the team may feel that is “lost in a see of information”. One technique that is commonly used to help in the design process is Quality Function Deployment (QFD). One of the main advantages of the QFD method is that it is organized to develop the major pieces of information necessary to understand a design problem: 3.2.2. Quality function deployment

M.

N.

Metric

1

1,3

2

2,6

3

1,3

4

1,3

5

4

6

5

7

5

8

6

Attenuation from dropout to handlebar at 10 Hz Spring preload Maximum value from the Monster Minimum descent time on test track Damping coefficient adjustment range Maximum travel (26 in. wheel) Rake offset Lateral stiffness at the tip Total mass Lateral stiffness at brake pivots Headset sizes Steertube length Wheel sizes Maximum tire width Time to assemble to frame Fender compatibility Instills pride Unit manufacturing cost Time in spray chamber without water entry Cycles in mud chamber without contamination Time to disassemble/assemble Special tools required for maintenance UV test duration to degrade rubber parts Monster cycles to failure Japan Industrial Standards test Bending strength (frontal loading)

9

7

10

8

11

9

12

9

13

9

14

9

15

10

16

11

17

12

18

13

19

14

20

15

21

16,17

22

17,18

23

19

24

19

25

20

26

20

Imp 3

Units dB

3

N

5

g

5

s

3

N-s/m

3

mm

3

mm

3

kN/m

4

kg

2

kN/m

5

in

5

mm

5

List

5

in

1

s

1

list

5

Subj.

5

US

5

s

5

cycles

3

s

3

list

5

hours

5

cycles

5

binary

5

kN

Table 3.1: List of metrics for a mountain bike suspension. The relative importance of each metric and the units for the metric are shown. “M.” and “N.” are abbreviations for the number of specification and the need it comes from. “Subj.” is an abbreviation indicating that a metric is subjective. (Adapted after Ulrich & Eppinger, 2000).

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c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

59

3.2 Setting product specification

3.2 Setting product specification

60

1. The specifications of the product. Date

Demand/

Design specification

Wish

Test/ Verification

Functional Requirements

3. What is important from the point of view of the customer.

1/25

D

Provide thrust for maximum height (velocity > (20 m/s)

of momentum analysis

1/25

D

Maintain stable vertical flight path (less

Flight tests with prototype

than 0.25 m deviation from vertical path)

Bernoulli and conservation

Design of experiments

Constraints 1/25

D

Rocket length ≤ 15 cm

Verify with engr. drawings during concept generation, detail design, etc.

1/26

D

2. How the competition meets the goals.

No detachable part less than

Verify with dimensional

5 cm in diameter

check of engr. drawings

Table 3.2: Specification sheet template, example of a toy rocket product (partial). Adapted after Otto & Wood (2001).

4. Engineering specifications to work toward. There are two points that are worth considering before applying QFD to a design problem. First, no matter how well it is taught that a design problem is understood, the design team should employ the QFD method for all original design or redesign projects. Second, the QFD technique can be applied to an entire product and its sub-systems. To apply the QFD methodology, the following steps should be followed: 1. Identify the customers. 2. Determine the requirements of the customers.

Specification category

Description

Geometry

Dimensions, space requirements, . . .

Kinematics

Type and direction of motion, velocity, . . .

Forces

Direction and magnitude, frequency,load imposed by, energy type,

Material

Properties of final products, flow of materials, design for manufacturing

efficiency, capacity, conversion, temperature Signals

Input and output, display

Safety

Protection issues

Ergonomics

Comfort issues, human interface issues

Production

Factory limitations, tolerances, wastage

Quality Control

Possibilities for testing

Assembly

Set by DFMA or special regulations or needs

Transport

Packaging needs

Operation

Environmental issues such as noise

Maintenance

Servicing intervals, repair

Costs

Manufacturing costs, material costs

Schedules

Time constraints

3. Determine the relative importance of the requirements. 4. Perform a benchmarking activity to determine how competition satisfy the customers. 5. Generate engineering specifications. 6. Set engineering targets. 7. Relate the requirements of the customers to engineering specifications. 8. Identify relationships between engineering requirements. Applying the above steps builds what is known as the house of quality. This house provides in a single picture all the pieces of information gathered by the design team and their relationships. As shown in figure 3.1, the house has many rooms, each containing valuable information.

Table 3.3: Categories for searching and decomposing specifications (After Franke, 1995).

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c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

61

3.2 Setting product specification

3.2 Setting product specification

62

The first step for documenting information in the house of quality is to determine the customer requirements and its relative importance. This information can be registered in the first room of the house: customer requirements. This room relates to what the customers want. The next step is to write down the information regarding the benchmarking activities carried out in the second room of the house: Customer targets and ratings. This room relates to now vs. what or how the customer are currently being satisfied.

Correlation Matrix How vs How

In this step, each competing product must be compared with the requirements of customers, rating each existing design on a scale of 1 to 5:

Relationship Matrix What vs How

1. 2. 3. 4. 5. Customer Targets and Ratings Now vs. What

Customer Requirements WHAT

Importance Rating

Engineering Design Specifications HOW

The The The The The

product product product product product

does not meet the requirement at all. meets the requirement slightly. meets the requirement somewhat. meets the requirement mostly. fulfills the requirement completely.

The benchmarking step is very important as it shows opportunities for both product improvement and gain in market share. If all the competition rank low on one requirement, that is clearly an opportunity, specially if the customer ranked that specific requirement as essential. After the engineering specifications have been generated, each one can be written in the third room of the house: engineering design specifications. This room relates how customer requirements will be measured to ensure satisfaction.

Targets How Much

Figure 3.1: Template for the House of Quality.

Hand in hand with the previous room is the targets room, which specify how much should be achieved. In this room all the target values related to each one of the engineering design specifications are stated. In many cases, extreme values for the delighted and disgusted states of customer satisfaction are also included for each specification. After the previous steps have been carried out, only two more steps are missing, to relate the requirements of the customers to engineering specifications and to identify relationships between engineering requirements. To relate the requirements of the customers to engineering specifications, the room at the center of the house, the relationship matrix, is used. In this matrix,

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c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

63

3.2 Setting product specification Indicator

Meaning

Strength



Strong relationship

9

Some relationship

5

4

Small relationship

3

Indicates no relationship

0

Blank

Table 3.4: Symbols used to indicate the level of relationship between customer requirements and engineering design specifications. Indicator

Meaning

Strength

⊕

Strong positive correlation

9

+

Some positive correlation

3

-

Some negative correlation

-1



Strong negative correlation

-3

Table 3.5: Symbols used to indicate the level of correlation between engineering design specifications.

3.2 Setting product specification

down the design process, but it does not. Time spent developing information is returned in time saved later in the process. Finally, it should be kept also in mind that QFD is a tool to build consensus. It is a tool to ensure that a variety of specifications from different areas converge to a successful product.

References 1. Jacobson, G. & Hillkirk, J. (1986) Xerox: American Samurai. 2. Franke, H. J. (1975) Methodische Schritte beim Klaren konstruktiver Aufgabenstellungen. Konstruktion. 27, 395-402. 3. Otto, K. & Wood, K. (2001) Product Design - Techniques in Reverse Engineering and New Product Development, Prentice-Hall. 4. Ullman, D. (2001) The Mechanical Design Process. Third Ed. McGrawHill. 5. Ulrich, K. & Eppinger, S. (2000) Product Design and Development. Second Ed. Irwin McGraw-Hill.

each cell represents how an engineering specification relates to a customer requirement. Although many parameters can measure more than one customer requirement, the strength of the relationship can vary. The strength of the relationship is represented through the specific symbols shown in table 3.4. To finish with the procedure, the roof of the quality house, the correlation matrix is filled. Here, the relationship between different engineering specifications is shown. The idea of the roof is to show that as one works to meet one specification, you may be having a positive or negative effect on others. For this purpose, the symbols shown in table 3.5 may be used. As the above steps are completed, the house of quality fills up. Figures 3.2 and 3.3 show two different examples of houses of quality for two different products. One hint for effectively using the House of Quality is that the matrix should not grow too large. If the house is larger than 50 rows and columns, then the design team should operate at different levels in the product. Another is to devote QFD as much time as needed. It may appear that QFD slows 3.2.3. Comments on QFD and the house of quality

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64

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

2

4

3

Easy to store

3

4

3

5

5

3

Brew larger amount

2

3

2

4

4

3

Contain steam

2

4

4

2

5

1

1

3

Technical Difficulty

3

4

Measurements Units

C

sec cup C

Object Target values

98 8.0

3

2

3

2

sec sec sec ft3

qt

44

0

30 0.2

?

98 << 4.75 88

5

20 0.4 2

1

20 0.2

5

20 0.4 1.5

3

3

3

100

Objective

West Bend

Measures

Mr. Coffee

?

WB Coffee Maker

98 na

0

Old Fashion Way

99

5

na hot

5

240 na

na 100

Powered Tea

na

na

na

25

5

60 na

na

Technical

Absolute

83 81

63 45

45

27 36

Importance

Relative

1

3

4

4

6

8

2

4.75 ? ?

5

Mountain Bike

3

Recumbent

3

BikeE CT

3

Amount of change in damping

Easy to clean

Amount of change in spring rate

3

# of tools to adjust

2

# number of tools to adjust

2

Rider height range

3

Rider weight range

3

Riders that notice pogoing

5

Max accel on 5.0 cm standard pothole

3

Easy to add tea

Max accel on 2.5 cm standard pothole

2

Max acceleration on standard street

West Bend Iced Tea Maker 1

2

66

Energy transmitted on standard road

Powdered Tea 5

2

3.2 Setting product specification

Environment Adjustability Performance

Old Fashion Way 5

3

Largest size of brew

1

5

Total Volume

4

Easy to add ice

Time to clean product

9

Time needed to add tea

Stronger tea

Volume of water in tank

West Bend Coffee Maker

Mr. Coffee Iced Tea Maker

Hottest temperature outside container

Temperature of exiting hot tea

Time water is in contact with tea

3.2 Setting product specification

Temperature of water in sleeping basket

65

Smooth ride on streets

1

3

3

Eliminate shock from bumps

1

2

4

No pogoing

5

2

1

Easy to adjust for different weights

5

3

2

Easy to adjust for different heights

5

3

3

Easy to adjust ride hardness

1

1

3

No noticeable temperature effect

5

4

4

No noticeable dirt effect

5

4

4

No noticeable water effect

5

5

5

Units

%

gs

BikeE CT

95

0.4 1.6 3.0 0.0 100 6.0 0.0 0.0 0.0 0.0

Mountain Bike

35

0.1 0.4 0.5 20

30

4.0 2.0 1.0 0.0 0.0

Recumbent

50

0.1 0.7 0.9 40

40

6.0 1.0 1.0 0.0 0.0

25

Target (delighted)

30

0.1 0.4 0.5 100 100 6.0 0.0 1.0 0.0 0.0

27 18

Target (disgusted)

50

0.2 0.7 1.0 50

2

6

? ?

gs

gs

%

lbs in

50

#

#

%

%

3.0 1.0 1.0 0.0 0.0

8

Figure 3.2: House of quality for iced tea maker (partial). After Otto & Wood (2001). c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Figure 3.3: House of quality for suspension system (partial). Adapted from Ullman (2003). c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

4.1 Brainstorming

68

Basic Methods

CHAPTER

Concept generation methods

4

6−3−5 Method

The Morphological Chart

Logical methods

Concept Generation

Brainstorming

TRIZ (TIPS) Axiomatic design

Figure 4.1: Some concept Generation methods. creates a tendency for designers to take their first idea and start to refine it toward a product. This is considered a very weak practice.

Up to now, all energies have been focused to understand the design problem and to develop its specifications and requirements. The goal now is to generate concepts that will lead to a quality product. A concept may be defined as an idea that is sufficiently developed to evaluate the physical principles that govern its behavior (Ullman, 2003). Hence, concepts must be refined enough to evaluate their form and the technologies needed to realize them. Concepts can be represented in rough sketches, flow diagrams, set of calculations or textual notes. In any case, each concept must contain enough details so the functionality of the idea can be ensured. Sometimes, design begins with a concept to be developed into a product. This is considered to be a weak philosophy and generally does not lead to quality design. In order to minimize changes later in the process, it is normally expected that the concept generation scheme should take 20-25 percent of the design process. It is very important for the design team to generate as many concepts as possible, following the old advice: Generate one idea, and it will probably be a poor one. Generate twenty ideas, and you may have a good one.

In order to avoid the previous problems, various methods aimed to generate concepts are presented here. Some may be more complicated to follow or have their particular value. In any case, it is a decision of the design team which to follow. Figure 4.1 shows the methods that will be discussed in this chapter. It is important to recall once more the importance of information gathering. Considered the first method for concept generation, this activity should be really the starting point of any concept generation method. This activity will include the search for documented ideas on solving problem functions that will increase the scope of possible solution generated by the design team. In the last chapter several sources of information were reviewed in the scope of the benchmarking activity. This sources are also valid here, and figure 4.2 shows a summary of them.

4.1

Brainstorming

It is a natural tendency to generate concepts as the design process progress, as it is naturally to associate ideas with things that we already known. This

Brainstorming is a group-oriented technique aimed to generate as many concepts as possible. The procedure is quite simple and has the advantage that a committed team can create a large number of ideas from different points of view. The guidelines for brainstorming are as follows:

c Copyright 2004 Dr. Jos´ e CarlosMiranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

69

4.1 Brainstorming Benchmarking

Product Function Product Architecture Patents Journals

Information Sources

Published media

Product Information Textbooks Consumer Products Periodicals

People

70

5. Avoid confining the group to experts in the area, that may limit the introduction of new ideas. Nature

Analogies

4.2 The 6-3-5 method

6. Avoid hierarchically structured groups. Bosses, supervisors and managers should not be included in many of the sessions. Some hints may be used to stimulate new thinking and the generation of new ideas: • Make analogies, think what other devices solve a related problem, even if they are applied to an unrelated area of application.

Goverment Reports

• Wish and wonder. Think wild. Sometimes silly, impossible ideas, give way to useful ones.

Professionals in Field

• Use related and unrelated stimuli. First, use photos of objects or devices that are related to the problem at hand. Next, use photos of objects unrelated to the problem. This activity usually gives way to new ideas.

Customers Experts

Figure 4.2: Information sources for concept generation. Many of this information can be found through the World Wide Web.

• Set quantitative goals. Set a reasonable number of concepts and do not leave the session until you have achieve them. For a group session, individual targets of 10 to 20 concepts is reasonable.

1. Form a group with 5 to 15 people. 2. Designate a person to work as facilitator to prevent judgments and encourage participation by all. Although some authors state that the facilitator should also be a contributor. Other suggest that the facilitator should only guide and record the session avoiding further participation. The latter allows the designation of the most participate person of the team as facilitator to encourage other team members to participate actively. 3. Brainstorm for 30-25 minutes. The first 10 minutes are generally devoted to introduce the problem at hand. The next 20-25 minutes sees the most generation of ideas, and during the last 10 minutes a sharp decline in ideas may happen. 4. Do not allow the evaluation of ideas, just the generation of them. This is very important. Ignore any comments about the usefulness, validity or value of any idea. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

4.2

The 6-3-5 method

One of the two main disadvantages with brainstorming is that first, all ideas are conveyed by words. Second, the generation of ideas can be dominated by one or two team members. The 6-4-5 method forces equal participation by all. The guidelines for the 6-3-5 method are also very simple: 1. Arrange teams around a table. Although 6 members are optimal, a number between 3 and 8 should suffice. 2. Establish a specific function of the product to work with. 3. Ask each member to draw in a sheet of paper two lines in order to create three columns. After that, ask each member to write, 3 ideas, one on each column, about how the function could be fulfilled. Ideas can be communicated by words, sketches or both. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

71

4.3 TRIZ

4.3 TRIZ

72

4. After 5 minutes of working in the concepts, pass the sheets of papers to the right.

Level

5. Give the participants another 5 minutes to add other three ideas to the list.

1

Apparent solution

32%

Personal Knowledge

10

2

Minor improvement

45%

Knowledge within company

100

3

Major improvement

18%

Knowledge within industry

1000

4

New concept

4%

Knowledge outside industry

100,000

5

Discovery

1%

All that is knowable

1,000,000

6. After completing a cycle stop to discuss the results and find the best possibilities. It is important to mention that there should be no verbal communication in this technique until the end. This rules forces interpretation of the previous ideas only from what it is on the paper.

Degree of inventiveness

Percent of solutions

Source of knowledge

Approximate number of solutions to consider

Table 4.1: Levels of Inventiveness.

4.3

TRIZ

The Teoriya Resheniya Izobreatatelskikh Zadatch (TRIZ) or Theory of Inventive Problem Solving (TIPS), was developed by Genrikh S. Altshuller in the former U.S.S.R. at the end of the 1940’s. The TRIZ theory is based on the idea that many of the problems that engineers face contain elements that have already been solved, often in a completely different industry for a totally unrelated situation that uses an entirely different technology to solve the problem. Based on this idea, Altshuller collaborated with an informal collection of academic and industrial colleagues to study patents and search for the patterns that exist.

The first two categories were designated as “routine design”, meaning that they do not exhibit significant innovations beyond the current technology. The last three categories represent designs that included inventive solutions. He also noted that as the importance of the innovation increased, the source of the solution required broader knowledge and more solutions to consider before an ideal one could be found. Table 4.1 summarizes this idea.

After spending 1500+ person-years studying at first around 400,000 patents (today the database extend up to 2.5 million patents), Altshuller discovered that they could be classified into five categories: 1. basic parametric advancement 2. change or rearrangement in a configuration 3. identifying conflicts and solving them with known physical properties 4. identifying new principles 5. identifying new product functions and solving them with known or new principles. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

73

4.3 TRIZ

PROBLEM TO SOLVE

SOLUTION

Find contradictions Contradiction Matrix

Apply Inventive Principles

1 2 3 4 n Inventive Principles

TRIZ Figure 4.3: TRIZ methodology. Based on his studies, Altshuller observed some trends in historical inventions: • Evolution of engineering systems develops according to the same patterns, independently of the engineering discipline or product domain. These patterns can be used to predict trends and direct search for new concepts. • Conflicts and contradictions are the key drivers for product invention. • The systematic application of physical effects aids invention, since a particular product team does not know all physical knowledge. In this regard, Altshuller noticed that almost all invention problems involved in one way or another the solution to a contradition. By contradition it is understood a situation in which the improvement of one feature means detracting another. The quality of the invention was in most occasions related to the quality of the solution to the contradiction.

4.3 TRIZ

74

1

Weight of movable object

21

Power

2

Weight of stationary object

22

Waste of energy

3

Lenght of movable object

23

Loss of substance

4

Lenght of stationary object

24

Loss of information

5

Area of movable object

25

Waste of time

6

Area of fixed object

26

Quantity of substance

7

Volume of movable object

27

Reliability

8

volume of stationary object

28

Measurement accuracy Manufacturing precision

9

Speed

29

10

Force

30

Harmful action at object

11

Stress or pressure

31

Harmful effect caused by object

12

Shape

32

Ease of manufacture

13

Stability of the object’s composition

33

Ease of operation

14

Strength

34

Ease of repair

15

Durability of a moving object

35

Adaptation Device complexity

16

Durability of a stationary object

36

17

Temperature

37

Measurement or test complexity

18

Illumination intensity

38

Degree of automation

19

Use of energy by moving object

39

Productivity

20

Use of energy by stationary object

Table 4.2: TRIZ 39 design parameters. Then, use the 40 inventive principles of TRIZ to generate ideas to overcome this problem. The 40 inventive principles were found by Altshuller to be the underlying principles behind all patents. This procedure is depicted in figure 4.3. Applying TRIZ principles allows the innovation without having to wait for inspiration. Practitioners of the TRIZ theory have a very high rate of developing new, patentable ideas.

Based on this premise, Altshuller devised TRIZ. The goal of using TRIZ is to find those contradictions that makes the design problem hard to solve. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

38 34

40 28

1

8 15

35 30

35 28

17 7

40 29

10 40 14 15

4

6. Area of stationary object

18 30

14 18 7. Volume of movable object

2 26

2 28 8

1 28

3

1

19

4

8 40 26

40 15 27 15. Durability of a movable object

1

5

5

4 10

7 37

18. Illumination intensity 19. Use of energy by moving object 20. Use of energy by stationary object

4 34 35

7 29 1 18 15

9

2 36 13 28

6 35 35 24

5 34 11

2

3. Length of movable object

28 2

2

10 27

19 6

8

35 19

29 34 14

4. Lenght of a stationary object

28 26 5. Area of movable object

3

15 6

40

7. Volume of movable object

9

36

4

7

2 34 28

35

35 40

35 33

15 10 2

4 10

15 22 35

34 18 37 40 10 14

18 4

2 11 39

28 10 34 28 33 15 10 35 2

13

19 39 35 40 28 18 21 16 40 8 13 10 18 10 3

14

7 17 15 26 14

10

2

19

5

1 40 35

2 19

16

28 25 35 35 23

2 28 35 10 35 39 14 22

39 18

40 18 4

36 30

10 13 26 19

35 19 32

19 32

2

16

26

10

19

12 28

15 19

35 13

8

25

18

13

14. Strength

39 3

32

12. Shape

18 4

35 34 6

11. Stress or pressure

10 30 13 17

38 3 35 35 38 34 39 35

10. Force

13. Stability of the object’s composition

3 14 26 13 3

27

3 21 19

1 35

15. Durability of a movable object

32 30 32 3

6

14

19 13

35 21 2

17 24

36 37

27

3

29

27 4 29 18

3

19

17. Temperature 18. Illumination intensity

35

35 7

2

4

12 8

6

10 15 10 20 19 6

29 1

35 26 18 26 24 15 2

19 13

29 35

29

28 10 28 24 26 30 29 24 35

15 15 32 19 32

3 26

20 28 18 31

35 39 23 10

25

26. Quantity of substance

23. Loss of substance

22. Waste of energy

17. Temperature

21. Power 1

14

19 10 15 17 10 35 30 26 26 4

29 30

32 18 30 26 2

6

13

10 14 30 16 10 35 2

18

17 32 17 7 30 6 7

39

18 39

4

15 36 39 2

35

10 18 2

13 18 13 16 34 10

34 10 7

30

10 39

35 16 35 3

35 34

32 18

6

4 28 30 10 13 8 19

15

22 2

18 40 4

34 39 10 13 35 35 34 35 6 38

8

10 24 10 35

18 22 28 15 13 30 35

6

19 35 14 20 10 13 13 26

26 14 35 5

36 2

35 10 19 2

35 10

19 17 1

14 27

21

10

9

18 19 3

35 39

14 24

10 35 2

3

35 38

38 2

40 27

19 2

10 37

14

36 37 18 37

5

36

36 10 36

18 36

25

3 37

37 36 10 14 36 4

14

35 29

14 34 36 22

19 32 32

34 14

2

3

5

10 17

35 1

13 19 27 4

32 35 14 2

2

14

35 27 15 32

9 13 27 39 3

15

10 35 35 23 32

32 3 27 15

6

10 37 14 29

10 40 17

4

40

29 38

35

22 14 13 15 2

9 25

6

10 19

19 35 28 38

16 19 35 14 15 8

29 30

30 14 14 26

29 18 27 31 39 6

30 40

35

27 3

30 10 35 19 19 35 35

10 26 35

35 28

29 3

26

40

29 10

10

35 28

31 40

28 10 27

27 3

19 35 2

19 28 6

19 10

28 27 10

20 10 3

10

39

35 35 18

35 38

4

19 18

3 18

16

36 40

28 20 3

18 38

10 16 31

19 18

32 30 19 15

2

22 40 39

36 40

21 16 3

17 25 35 38 29 31

35 19 2

19

6

32 19

32

35

19

19. Use of energy by moving object

5

19 28 35

19 24 2

9

35 6

3

20. Use of energy by stationary object

35

18

15

14 19

17

1 32 35 32 1

15

14 21 17 21 36 19 16 13 1 1

6

35

28 18 10 40

27 16 10

10 30 19 3

27

35 16 26 23 14 12 2

4

16. Durability of a stationary object

2 19 32 32

25

35

10 35 39

14 6 35

3 14 18 40 35 40 35

3 35 19

19 30

35 22 1

9 8

9. Speed

40

33 1

9 14

2

35 3

16

17 15

1 18

2 35 15 35 10 34 15

9 40 10 15

8. Volume of stationary object

40 34 21 35 4

21

24

38 18

2

15 7

1 39

7

3 34

4

19 3

40 14 6. Area of stationary object

8

35 3

28 1

10 15 32 1

5 35

18 19 15 19 18 19 5

32 22 32

19 30 38 1 15 28 10

6 18 35 15 28 33

11

27 28 19 35 19

2

24. Loss of information

18 31 34 19 3 31

20. Energy expense of fixed object

13 36 6

34 31

16. Duration of fixed object’s operation

25 12

38 32

28 27 5

25. Waste of time

15. Duration of moving object’s operation

29 19 1

4

What is deteriorated? 2. Weight of a stationary object

4 13 39 2 38

6

14. Strength

13. Stability of the object’s composition

12. Shape

35

14

2

6

6 35

6 35 36 35

19 1

19 9

8

18 21 10 35 35 10

36 37 12 37 18 37 15 12

3 17

9

1

7

15 19 38 40 18 34

32 2 8 31

11. Stress or pressure

13 28

8 35 28 26 40 29 28

9

15

2 36 28 29

4 15 35

2 19 6 27

12 18

10. Force

9. Speed

4

8

5 34

1 28 1 15 15 14

1. Weight of a movable object

1 40

1 14 13 14 39 37 35

29 30 19 30 10 15

14 16 36 28 36 37 10

19 16 6 38 32

28 10

34

15

36 22 22 35 15 19 15 19

17. Temperature

8

2 14

2 18 24 35

1 10 15 10 15

9

34 31

16. Durability of a stationary object

35

1

34

18 40 31 35

What should be improved?

10 29 15 34

37 34

21 35 26 39 13 15 2 39

35

8

9 36

1 35

35 36 36 37

29 30

10 36 13 29 35 10 35

1

4

8

38 34 36 37 36 37 29

8

29 40 26

14. Strength

8

29

8 10 15 10 29 34 13 14

13. Stability of the object’s composition

4 35

2 14

37 40 10 18 36 12. Shape

1

1 18 10 15

1 18 13 17 19 28 10 19 10

37 18 11. Stress or pressure

4 17 10

7

13 14

13 38 10. Force

13

4 17 19 14

9. Speed

19 35 10 18 29 14

7 17

7

35 10 19 14 35

8. Volume of stationary object

8 10 10 36 10 14

8 10 13 29 13 10 26 39

2

9 39 1

29 40

14

17 26

8

15 38 18 37 37 40 35 40 19 39

7 14

4

2

2 5 35

2

4

2 17 29

13 15 17

29 34

2

76

19. Energy expense of movable object

29 34 29 35

5. Area of movable object

8. Volume of fixed object

29

10

4. Lenght of a stationary object

7. Volume of movable object

29 17

2. Weight of a stationary object 3. Length of movable object

6. Area of fixed object

8

4.3 TRIZ

18. Illumination

15

1. Weight of a movable object

5. Area of movable object

3. Length of fixed object

2. Weight of a fixed object

What is deteriorated? What should be improved?

4. Lenght of a stationary object

4.3 TRIZ

1. Weight of a movable object

75

35 28 3

35 17

21 18 30 39 1

6

6

19 1

1

19

26 17

19 12 22 35 24

37 18 15 24 18 5

35 38 34 23 19 18 16 18

19 2

28 27

3

35 32

18 31

31

Figure 4.4: TRIZ contradiction matrix.Continued.

Figure 4.5: TRIZ contradiction matrix. Continued.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

35

3

28

35 17 22 37 1

4

39 9

15 17 15 1

29 37 17 24

15 29 32 28

5. Area of movable object

29

6. Area of stationary object

32 35 26 28 2 40 4

32 3

7. Volume of movable object

14 1

25 26 25 28 22 21 17 2

28

3

2 32 1

28 1 29 27 2

25

19 27 35 28 2

10 13 6

12. Shape

10 40 28 32 32 30 22 1

35 22 2 37

15 13 10

40

30 12

2

24 35 13 32 28 34 2

33

35

1

13 12 28 27 26

15 37 1 3

2

1

32 32 15 2 13 1 1 15

11 2

3

16. Durability of a stationary object

34 27 10 26

17. Temperature

19 35 32 19 24

13

30

27 18 35 15 35 11 3

6 40 24

22

3

3

35 10 1

27

13

1

2

22 33 22 35 26 27 26 27 4 35 2

11 15 3

2 24

16

35

37

32 39 28 26 19

19. Use of energy by moving object

19 21 3

1

35

2 35 28 26 19 35 1

11 27 32

6

27

6

20. Use of energy by stationary object

10 36

10 2

23

22 37 18

30

19 22 1

19 28 18 9

6

13 7

35 6

14 29 10 28 35 2

35 6

6 38

15 26 17 7

10 18 1

10 20 10 20 15 2

30 24 26 4

37 35 26 5

14 5

35 6

29

27 26 29 14

8

5

15 14 2 29

15 29 17 10 32 35 3

10 40 8

28 14 4

28 11 14 16 40 4

15 40

10 14

19 29 6

20 10

6

16 38

17 3

35

15 28 35 31 19 16 35

16 6

14 19

25 14 1

36. Device complexity

32 32 15 2

13

26 2

10

2 29 35 38 32 2

25

16

19 35

1

6

14 3

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

13. Stability of the object’s composition 17 40

28 10 24 35 1

2 32 28 33 2

29 37 10

22 17 1

32 3

1

6

29 32 28 25 10 10 28 28 19

29 32 18 36 2 18 22 1

27 2

35

32

34 36

33 28 39 35 37 35 19 27 35 28 39 18 37

29 15 17 13 1

15 16 36 13 13 17 27

26 12

25 2

1

6

13 1

17

13 15 1

25 13 12

2

27 1

27 2

35 4

16 40 13 29 35 1

40

28 3

18 15 13 16 25 25 2 32

1

29 16 29 2

16

29 7

19 26

14 1

28 26 28 26 14 13 23

17 14

35 13

18 35 35 10 28 17

13

16

13 2

34 31 17 7

27 39

32 15 34 32 35

12 11 13

29 28 30 1

13 2

2

4

20

2

1

18 3

35 4

35

22

28 15 17 19 39 39 30

35 13 35 15 32 18 1 1

34 10 10 2

14

36 28 35 36 27 13 11 22

28 10 2 35 37

8

29 13 2

16 26 31 16 35 40 19 37 32 1

6

28 11 13

37 13 27 1

16 34 10 26 16 19 1 28

39 29 1

30 14 10 26 10 35 2

1

35 40

35 10 15 17 35 16 15 37 35 30

6

18 17 30 16 4

28 38 26 7

35

14

38. Degree of automation

26 24

1

35 24

35

33 35 1

10

36 34 26 1

2

13 16 17 26

24 37 15 3

1

34 9

29

27 26 6

35 26 28 27 18 4

1

35 35 30 15 16 15 35 6

3

40 27 18

18 18 13 28 13 2

35 11

19 15 35 1

28 13 28 1

8

16 4

30 18

22 1

35 13 35 12 35 19 1

13 16 15 39 35 15 39 31 34

6

26 1

30 18 35 28 35 28 2

40

17 18 16 1

15 8

26 30 2

17 2

23 1

13

40

22 23 34 39 21 22 13 35 22 2

3

28 32 35

32

3 35 32 30 30 18

27 39 13 24 39 4

22 1

28 6

13

28 15 10 37 10 10 35 3 10 36 14

16 25

Figure 4.6: TRIZ contradiction matrix. Continued.

12. Shape

10. Force

9. Speed 21 35 8

32

3 16 32 3

14 24 24

37. Measurement or test complexity

39. Productivity

35

34 28 3

13 16

12 28

35 29 35 14 10 36 35 14 15 2

10 2 35

34 36 35 39 26 24

27 26 2

10 35 3

6

1

14

30 40

34 17 22 5

32 24

16

35 11 35 11 10 25 31 35. Adaptation

4

26 28 25 26 5 13 18 27 9

10 35 17

36 5

35 19 16 11

22 21 2

34. Ease of repair

10 37 36 37 4

28 13 32 2

30. Harmful action at object

29 35

35 16

11 28 10 3

27 1

15

5

32 35 28 35 28 26 32 28 26 28 26 28 32 13

28 29 1

13 27 3

5

29

10 15 9

28 32 28 35 10 28

33. Ease of operation

3 36 29 35 2

22 26 32

18 15 20

40 4

32. Ease of manufacture

40 3

39 6

39 10 13 14 15

34 10 32 18

3

29. Manufacturing precision

23 35

2

10 35 2

16 17 4

34 10 8

29 3

5

1

35 35 22 1

14 2

30 26 30 16

26 26

40 15 31

38

10 24 10 35 1

18 39 40

22 26 39 23 35

2

16 35 36 38

10 31 39 31 30 36 18 31 28 38 18 40 37 10 3

17 2

32

18 7

17 30 30 18 23

39 16 22

28 39

7

22 10 29 14 35 32

36 35 35

23 40 22 32 10 39 24

3

28. Measurement accuracy

6. Area of fixed object

5. Area of movable object

2

11. Stress or pressure

4. Lenght of a stationary object

3. Length of fixed object

2. Weight of a fixed object

39. Productivity

38. Degree of automation

What is deteriorated?

7

15 39 1

35 37

17 28 13 16 27 28 4

2

19 22 35 22 17 15

18 2

15 15 17

15 35 26 2

25

19 6

18 31 18 35 35 18

36 35 24 10 14

29 35 39 35

13 16 19

30 6

13 38 38

31. Harmful effect caused by the object

35 10 4

27

19 38 17 32 35 6

17 26

28

32 15 19 35 19 19 35 28 26 15 17 15 1

32 1

10 2

26. Quantity of substance

3 28 35 37

10

16 29 15 13 15 1

40 33

3 10 24

37. Measurement or test complexity

36. Device complexity

2

15 35 30 2

10 16 34 2

12 27 29 10 1

16 40 33 28 16 22 4 17 1

19 1

32 40 27 11 15 3 2 2

10 32 28 2

27 22 15 21 39 27 1

29

25. Waste of time

3 34 10 18 2 35

15 6

35

35 37

4 34 27 16

35

24. Loss of information

27. Reliability

10 2

18 20 10 18 10 19

35 24 35 40 35 19 32 35 2

15. Durability of a movable object

2 17

15 17 26 35 36 37

17 28 26

22 2

17 7 16 24 34

25 11

1 35 11

26

29 26 35 34 10 6 2

28 15 1

18

37 1

31

23. Loss of substance

10 15

30 18

15 10 10 28

27 18 16 35 1

35 23

26

13

27 3

1

22. Waste of energy

36 14 30 10 26

26 18 28 23 34 2

1 18 2

15 29 26 1

1

2

3

13 15 16

2

36 19 26 1

38 31 17 27 35 37

30 14

4

40

16

18. Illumination intensity

16

1

3

26 26

15 17 15 13 15 30 14 1

8

21. Power

17 26 14 4

7

18 30 27 39 11 3

35. Adaptation

34. Ease of repair

33. Ease of operation

35 1

4

35 13 3

11. Stress or pressure

14. Strength

15 35

1

25 3

19 35 1

36

16 27 35 40 1

3 35 35 10 28 29 1

13. Stability of the object’s composition

26 39 17 15 35

What should be improved?

1 28

16 26 24 26 24 24 16 28 29

13 21 23 24 37 36 40 18 36 24 18 1 19 35 25

2 26

1

4 10

29 1

24 32 25 35 23 35 21 8

28 3

10 25 28

35

40 16 16 4

35 10 34 39 30 18 35

16

32 28 11 29

18 36 39 35 40

11 35 28 32 10 28 1

10. Force

27 19 15 1

18 39 26 24 13 16 10 1 22 1

2

27 28 1

1

36 34 26 32 18 19 24 37

1 28 14 15 1

13 1

2

35

13 2

26 30 28 29 26 35 35 3

27 32 22 33 17 2

40 11 28 16

27 29 5

6

15 17 2

10

9 26 28 2 32 3

9. Speed

18

2

24 28 11 15 8

29 15 29

17

4. Lenght of a stationary object

8. Volume of stationary object

32. Ease of manufacture

31. Harmful effect caused by object

2 19 35 22 28 1

10 14 28 32 10 28 1 29 40

36 2

8. Volume of fixed object

10 28 18 26 10 1 8

3. Length of movable object

35 26 26 18 18 27 31 39 1

78

7. Volume of movable object

27 2. Weight of a stationary object

30. Harmful action at object

3 11 1 28 27 28 35 22 21 22 35 27 28 35 3

4.3 TRIZ

1. Weight of a movable object

1. Weight of a movable object

28. Measurement accuracy

27. Reliability

What should be improved?

29. Manufacturing precision

4.3 TRIZ

What is deteriorated?

77

Figure 4.7: TRIZ contradiction matrix. Continued.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

34 40 22 39

22. Waste of energy

26 10 19 35 16

2

28

17 25 19

10 38

26

14 16

19 38 1 7

23. Loss of substance

31 40 3

6 16

38

13 6

10

3

18 38

38

10 6

37

32 7

18

21. Power 22. Waste of energy

25

15 18 6

24 5

31

35 10 10 24

10 19 19 10

24 26 24 28

12 31 18 38 2

3

23. Loss of substance 24. Loss of information

28 32 35 25. Waste of time

29 3

26. Quantity of substance

14 35 3

20 10 28 20 35 29 1

19 35 38 1

35 20 10 5

28 18 28 18 10 16 21 18 26 17 19 18 35 3

35 3

34 10 10 40 31 27. Reliability

11 28 2 3

28. Measurement accuracy 29. Manufacturing precision

28 6 32 3

10 26 6

32

24

27 3

27

35 35

18 35 22 15 17 1 37 1

13 19 6

1

26 31 35

3

3

6

32

19 26 3

32 32 2

22 33 1

19 1

32 13 6

15 35 15 22 21 39 22 35 19 24 2 22 2

33 31 16 22 2

32. Ease of manufacture

1

27 1

33. Ease of operation

32 40 29 3 3

28 8

34. Ease of repair

1

11 11 29 1

2

9

35. Adaptation

18 25 25

27 1

18

27 1

6

28 32 32

32 2

13 32 35 31

32 26 32 30

2

28 18

10 24

6

19 22 21 22 33 22 22 10 35 18 35 33 35 2

19 40 2

35 21 35 10 1

10 21 1

22 3

29

24

22 2

27 1

19 35 15 34 32 24 35 28 35 23 33

39 1

18 16 34 4

19 28 32 4

10 4

1

1

10 13

2

24 27 22 10 34

10 15 1

15 1

15 10 15 1

2

35

13

28 16

32 2

32 19 34 27

10 25 10 25

22 19 35

19 1

18 15 15 10

35 28 3

29

1

13 1 35

3

35 26 1

13 10 4

2

17 24 17 27 2

2 28

28 15

37. Measurement or test complexity

27 3

19 29 25 34 3

38. Degree of automation

25 13 6

13

6

13 27 2

29 13

26 2

8

29 28

19

19

30 34 13 2 16

32

13

2 32 13

35 3

6

27

35 20 28 10 28 10 13 1

10 18 2

10

38 19

29 35 35 23 5

28. Measurement accuracy 29. Manufacturing precision 30. Harmful action at object 31. Harmful effect caused by the object

23

35

27

29 18

2

34

10

22

2

10 28

22 10 10 21 32

27 22

23

1 28 32 28 18 34

18 3

3

2

34. Ease of repair

39. Productivity

38. Degree of automation

37. Measurement or test complexity

36. Device complexity

34. Ease of repair

35. Adaptation

28 10 29 35

24 34 27 2

28 24 10 13 18

10 23

35 33 35

13 23 15

4 28 32 1

18 39 34 4

10 34 10

3 35 29 1

35 29 2

11 32 27 35 35 2

35 28 6

27 17 1

40 40 26

32 10 35 30 32 15 3

35 1

13 3

27 8

35 13 29 3

27 35

8

27 10 29 18 24 1

28

27 29 38

11

28 24 3

23

22 26 39 10 25 18 17 34 13 11 2

10 34 32 28 10 34 28 32

11 32

26 28 4

26 2

26 28 10 18

1

10 36 34 26

18

18 23 32 39

17

1 24 35 2

2

2

24 2

3

33 4

40 39 26 1

28 39 2

35

24 2

2

25

2

34 35 23 28 39 2

1

16

1 31

26 26 24 22 19 19 1

10 34 32

29 40

27 40 26 24

38. Degree of automation

11 27 28 26 28 26 2 1

32 28 10 34 18 23

35 1

13 24 22 35

2

10 32 1

22 19 2 29 28 33 2

35 1

1 21 5

16 7 1 5

32 1

16 12 17

34 35 1

16

13 11

7

16

15 29 1

27 34 35 28

4

37 28

35

13 29 15 28 37

12 26 1

13

34 3

22 35 35 22 35 28 1

10 38 34 28 18 10 13 24 18 39 2

12 1

24 7

13

28 1

28

35 1

1 32 1

6

37 28

28 34 21 35 18 24 5

15 24 34 27

35 10

37

12 17

15 15 10

35 27 4

32

13 10

15 10 15 1

37 28

26 1

10 28 34 15 1

714

11 29 1

1 12 3

13 9 26 24 28 2

11 1

28 35 1

1 12

27 26 27

18 39

28 8 1

13 15 34 1 1

27 1

13 27 26 6 1

21 2

12 26 15 34 32 25

11 10 26 15

32 31

10

5

12

25 10 35 10 35 11

28 8

35 1

3 22 31

19 1 3 2

13 16 11 19 15 32 2

8 1

5

10 34

22 31 29 40 29 40 34 1

35 13 35 5 13 35 2

25 35 10 35 11 22 19 23 19 33

17

16 13 24 1

32 25 10

34 26

17 27 25 13 1 40 2

32 13 35 27 35 26 24 28 2

35 23

27 24 28 33 26 28 40 23 26 10 18

13 1

3

11 13 35 13 35 27 40 11 13 1

40

33 6

29 18 28 24 28

1

37. Measurement or test complexity

39. Productivity

2

23 35 3

5

1

36. Device complexity

34

7

22

33 30 35 33

2

17

35 15 10 35 10 35 18 35 10 28 35

29 31 40 39 35 27 10 25 10 25 29

11 10 10 2

35. Adaptation

19

28 35

30 34 16 15 23

39 35 31 28 24 31 30 40 34 29 33

4

19 17 20 19 19 35 28 2

10 34 34

15 34 32 28 2

12 18 33. Ease of operation

33. Ease of operation

32. Ease of manufacture

31. Harmful effect caused by the object

35 26 10 26 35 35 2

18

10 29 16 34 35 10 33 22 10 1

32 35 38

30. Harmful action at object

29. Manufacturing precision

28. Measurement accuracy

1

32. Ease of manufacture

35 30

29 28 35 10 20 10 35 21 26 17 35 10 1 18 16 38 28 10 19 1

28

23 28 35 10 35 33 24 28 35 13 18 5

35 2

11 23 1

27 10

18 35 33 18 28 3

16 10 15 19 10 24 27 22 32 9 28 2

35

8 2

29 13 3

28 29 1

35 32 2

32 3

15

20 19 10 35 35 10

24 35 38 19 35 19 1

35 35 16 26

2

21 22 21 35

24

28 12 35

32 1

11 10 32

27. Reliability

29 31

18

2

34

34

31 2

3

24 34 2

35 34 2

24

40

27

31 28

19 22 2

26 31 2

28 40 28

13

16 27 2

24

4

4

19 24 32 15 32 2

10 30 24 34 24 26 35 18 35 22 35 28

18 16

29 39

12 24

13

32 6

9

10 24 35

25. Waste of time 26. Quantity of substance

24 28 35 38

26 32 10 16

35 19 22 2

35 3

15 28 25 39 6

3

4

28 27 2

18 6

32

27 22 37 31 2

24 39 32 6

16 26 27 13 17 1

36. Device complexity

39. Productivity

24 10 2

35 16 27 26 28 24 28 26 1 1

18 16

27 19

28 24 32

33 28 40 33 35 2

10 32 4

18 32 10 39 28 32

35 11 32 21 17 36 23 21 11 10 11 10 35 10 28 10 30 21 28

31. Harmful effect caused by the object

3

35 38

25

40 30. Harmful action at object

35 18 24 26

7

16 18 31

40 10

28 6

10 6

34 29 3

39

35 34 27 3 25 6

17

27. Reliability

What should be improved? 34

35 18 28 27 28 27 35 27

19

80

19

35 27 19 10 10 18 7 2

4.3 TRIZ

What is deteriorated?

26. Quantity of substance

25. Waste of time

24. Loss of information

23. Loss of substance

22. Waste of energy

21. Power

20. Energy expense of fixed object

10 35 28 27 10 19 35 20 4

19 37

18 18 38 39 31 13

10

6

32 15

35 28 28 27 27 16 21 36 1

24. Loss of information

19. Energy expense of movable object

18. Illumination

17. Temperature

16. Duration of fixed object’s operation

14. Strenght

What should be improved? 21. Power

15. Duration of moving object’s operation

4.3 TRIZ

What is deteriorated?

79

35 12 17 35 18 5

19 10 25 28 37 28 24 27 2

Figure 4.8: TRIZ contradiction matrix. Continued.

Figure 4.9: TRIZ contradiction matrix. Continued.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

12

35 26

25 12

35 26

81

4.3 TRIZ

From the patents studied, Altshuller extracted 39 design parameters that cause conflict. These 39 parameters are listed in table . To effectively use these parameters, it is necessary to find those two that are cause of conflict in a given design. Consider for example that a non-moving mechanical component needs to be lighter but remain as strong. From the 39 design parameters, find the principle that needs to be changed, in this case, “Weight of stationary object” (principle #2). Then find the parameter that is negatively affected, in this case, “Strength” (principle #14). Then, using the contradictions matrix shown in figure 4.9, find those inventive principles that are candidates to solve the conflict. From the contradictions matrix, the inventive principles that solve the contradiction between “Weight of a stationary object” and “Strenght” are 2, 10, 27 and 28.

4.3.1. 39 design parameters

4.3 TRIZ

82

• To scare birds from buildings and airports, reproduce the sound of a scare bird using a tape recorder. • Hovercraft. 3. Principle of local quality • Change the structure of the object or environment from homogeneous to non-homogeneous. • Have different parts of the object carry out different functions. • Place each part of the object under conditions most favorable for its operation. Examples:

4.3.2. Forty inventive Once the matrix has been used to find those inventive principles principles candidates to solve the engineering contradiction, they can be applied to generate solutions for the problem at hand. These inventive principles can also be used independently of the contradiction matrix as a source of ideas to solve conflicts. The forty TRIZ design principles to solve engineering conflicts are:

• Fuselage skin of commercial airplanes. • Stapler. A pencil and an eraser in one unit. 4. Principle of asymmetry • Make an object asymmetrical. • Increase the object asymmetry.

1. Principle of segmentation Examples: • Divide an object into independent parts that are easy to disassemble. • Increase the degree of segmentation as much as possible. Examples: • Sectional furniture, modular computer components, folding wooden ruler, food processor. • Garden hoses can be joined together to form any length needed. Drill shafts. 2. Principle of removal • Remove the disturbing part or property of the object. • Remove the necessary part or property of the object. Examples: c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

• Eccentric weight on motor creates vibration. 5. Principle of joining • Merge homogeneous objects or those intended for contiguous (adjacent) operations. • Combine in time homogeneous or contiguous operations. Examples: • TV/VCR, Cassette tape heads. • The working element of a rotary excavator has special steam nozzles to defrost and soften frozen ground in a single step. 6. Principle of universality • Let one object perform several different functions. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

83

4.3 TRIZ • Remove redundant objects. Examples: • Sofa which converts from a sofa in the daytime to a bed at night. Fingernail clipper. 7. The nesting principle • Place one object inside another, which in turn is placed in a third, etc. • Let an object pass through a cavity into another. Examples:

4.3 TRIZ

84

• Set up the object such that they can perform their action immediately when required. Examples: • Cutter blades ready to be snapped off when old. • Correction tape. 11. Principle of introducing protection in advance • Compensate for the low reliability of an object by introducing protections against accidents before the action is performed. Examples:

• Telescoping antenna, stacking chairs.

• Fuses, electric breakers. Shaft couplers.

• Mechanical pencil with lead stored inside.

• Shoplifting protection by means of magnetized plates in products.

8. Principle of counterweight • Compensate for the weight of an object by joining it with another object that has a lifting force. • Compensate for the weight of an object by interaction with an environment providing aerodynamic or hydrodynamic forces.

12. Principle of equipotentiality • Change the conditions such that the object does not need to be raised or lowered. Examples: • Pit for change oil, Loading dock, airport gate.

Examples: • Boat with hydrofoils, hot air balloon. • Rear wings in racing cars to increase the pressure from the car to the ground. 9. Principle of preliminary counteraction • Perform a counter-action to the desired action before the desired action is performed. Examples: • Reinforced concrete column or floor. Reinforced shaft. 10. Principle of preliminary action • Perform the required action before it is needed. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

13. Principle of opposite solution • Implement the opposite action of what is specified. • Make a moving part fixed and the fixed part mobile. • Turn the object upside down. Examples: • Abrasively cleaning parts by vibrating the parts instead of the abrasive. • Lathe, Mill. 14. Principle of spheroidality • Switch from linear to curvilinear paths, from flat to spherical surfaces, etc. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

85

4.3 TRIZ • Make use of rollers, ball bearings, spirals.

4.3 TRIZ

86

• Switch from direct to rotation motion.

• A computer mouse where a 2D screen is transformed into a horizontal mouse pad.

• Use centrifugal force.

• A composite wing where loads are in only one direction per layer.

Examples:

18. Use of mechanical vibrations

• Computer mouse.

• Make the object vibrate.

• Screw lift.

• Increase the frequency of vibration.

15. Principle of dynamism • Make the object or environment able to change to become optimal at any stage of work. • Make the object consist of parts that can move relative to each other. • If the object is fixed, make it movable. Examples: • A flashlight with flexible neck. • Bicycle drivetrain and derailer. 16. Principle of partial or excessive action • If it is difficult to obtain 100% of a desired effect, achieve somewhat more or less to greatly simplify the problem.

• Use resonance, piezovibrations, ultrasonic, or electromagnetic vibrations. Examples: • Vibrating casting molds. • Quartz clocks. 19. Principle of periodic action • Use periodic or pulsed actions, change periodicity. • Use pauses between impulses to change the effect. Examples: • Hammer drill. • Emergency flashing lights. 20. Principle of uninterrupted useful effect

Examples: • Keep all parts of the object constantly operating at full power. • Raincoats, snowboards. 17. Principle of moving into a new dimension • Increase the degrees of freedom of the object. • Use a multi-layered assembly instead of a single layer. • Incline the object or turn it on its side. • Use the other side of an area. Examples: c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

• Remove idle and intermediate motions. Examples: • Steam turbine, mechanical watch. 21. Principle of rushing through • Carry out a process or individual stages of a process at high speeds. Examples: c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

87

4.3 TRIZ • Cutting thin wall plastic tubes at very high speeds so cutting action occurs before deformation.

22. Principle of turning harm into good

4.3 TRIZ

88

• Nail resistant tires. 26. The copying principle

• Use harmful factor to obtain a positive effect.

• Instead of unavailable, complicated or fragile objects, use a simplified cheap copy.

• Remove a harmful factor by combining it with other harmful factors.

• Replace an object by its optical copy, make use of scale effects.

• Strengthen a harmful factor to the extent where it ceases to be harmful.

• If visible copies are used, switch to infrared or ultraviolet copies.

Examples: • Medical defibrillator. Use of high frequency current to heat the outer surface of metals for heat treatment. 23. The feedback principle • Introduce feedback. • If feedback already exists, reverse it. Examples: • Air conditioning systems. • Noise canceling devices. 24. The go between principle • Use an intermediary object to transfer or transmit the action. • Merge the object temporarily with another object that can be easily taken away. Examples: • Gear trains. 25. The self service principle • The object should service and repair itself. • Use waste products from the object to produce the desired actions. Examples: c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Examples: • Rapid prototyping. Crash test dummies. • Measure shadows instead of actual objects. 27. Cheap short life instead of expensive longevity • Replace an expensive object that has long life with many cheap objects having shorter life. Examples: • Inkjet printer heads embedded in ink cartridges. Cardboard box. 28. Replacement of a mechanical pattern • Replace a mechanical pattern by an optical, acoustical or odor pattern. • Use electrical, magnetic or electromagnetic fields to interact with the object. • Switch from fixed to movable fields changing over time. • Go from unstructured to structured fields. Examples: • CD player. • Microwave oven. Crane with electromagnetic plate. 29. Use of pneumatic or hydraulic solutions • Replace solid parts or an object by gas or liquid. Examples: c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

89

4.3 TRIZ • Power steering. Bubble envelopes.

30. Using flexible membranes and fine membranes • Replace customary constructions with flexible membranes and thin film. • Isolate an object from outside environment with thin film or fine membranes. Examples: • Dome tent. High Altitude Balloon. 31. Using porous materials • Make the object porous or use porous elements. • If the object is already porous, fill the pores in advance with some useful substance. Examples: • Running shoe soles. Air filters. 32. The principle of using color • Change the color or translucency of an object or its surroundings. • Use colored additives to observe certain objects or processes. • If such additives are already used, employ luminescence traces. Examples: • Transparent bandage. Roadway signs. 33. The principle of homogeneity • Interacting objects should be made of the same material, or material with identical properties. Examples: • Shaft and bushing. 34. The principle of discarding and regenerating parts c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

4.3 TRIZ

90

• Once a part has fulfilled its purpose and is no longer necessary, it should automatically be discarded or disappear. • Parts that become useful after a while should be automatically generated. Examples: • Multistage rockets. Bullet castings. 35. Changing the aggregate state of an object • Change the aggregate state of an object, concentration or density, the degree of flexibility or its temperature. Examples: • Heat packs. Light sticks. 36. The use of phase changes • Use phenomena occurring in phase changes like change of volume and liberation or absorption of heat. Examples: • Fire extinguisher. 37. Application of thermal expansion • Use expansion or contraction of materials by heat. • use materials with different thermal expansion coefficients. Examples: • Thermometers. Bimetallic plates. 38. Using strong oxidation agents • Replace air with enriched air or replace enriched air with oxygen. • Treat the air or oxygen with ionizing radiation. • Use ionized oxygen or ozone. Examples: c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

91

4.4 The morphological chart • Metal forming ovens. Torch cutting.

Convert Electrical Energy to Translational Energy

39. Using an inert atmosphere • Replace the normal environment with an inert one. • Carry out the process in a vacuum. Examples: • Aluminum cans for beverages. Arc welding. 40. Using composite materials • Replace a homogeneous material with a composite one. Examples: • Steel belted tires. wings.

4.4

Tennis racquets.

4.4 The morphological chart

High performance aircraft

The morphological chart

The aim of the morphological chart is to generate a complete range of alternative design solutions for a product widening the search for potential new solutions. It is based on the use of identified functions to foster ideas and has two parts. First, to generate as many concepts as possible. Second, to combine the individual concepts into overall concepts that meet all functional requirements. The procedure to create and use a morphological chart is quite simple and can be summarized as follows: 1. List the features or functions that are essential to the product. Each function will be a row of the chart. The list of functions should contain all the features that are essential to the product, at an appropriate level of generalization. If a QFD procedure has been already performed, the list of customer requirements can be used as the list of functions. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

92

Rotary motor with transmission

Linear Motor

Accumulate Energy

Spring

Moving mass

Apply Translational Energy to Nail

Simgle impact

Multiple impacts

Solenoid

Rail gun

Push nail

Figure 4.10: Morphological table for a hand-held nailer. Adapted from Ulrich & Eppinger (2000). 2. For each feature or function, list the means by which it may be achieved. These lists will be the columns of the chart. Lists might include new ideas as well as known solutions. 3. After the chart has been filled out, identify feasible combinations of subsolutions. Each combination will be a possible solution to identify. Figure 4.10 shows an example of a morphological chart for a hand nailer presented by Ullrich & Eppinger (2000). The rows in the table correspond to the functions identified by the design team: convertion of electrical energy to translational energy, acummulation of translational energy and application of translational energy to the nail. The entries in each column correspond to possible solutions for the function at hand. It is important to notice that in order for the chart to be most useful, the items in the list of functions should all be at the same level of generality, and they should be as independent of each other as possible. The list should not be too long, however, and no more than 10 functions should be considered. Some authors advice to use no more than 4 functions at a time. If some functions are to be disregarded for this matter, the development team must clearly understand the risks and tradeoffs of not taking them into consideration. It is also advisable to arrange solution principles so that the columns create logical grouping, for example, of mechanical type, of electrical type, etc. Also, sketches should be used whenever possible to convey as much information as possible. Finally, consideration should be given only to solutions that meet the estimated engineering specifications. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

93

4.4 The morphological chart

Once the chart is filled with solutions to all the specific functions listed, the next step is to consider combinations from the range of all possible solutions. Usually a large number of combinations is possible, although restrictions apply as not all combinations of solutions are possible, for example, combinations that have intrinsic incompatibilities should be discarded.

Rotary motor with transmission

Linear Motor

Accumulate Energy

Spring

Moving mass

Apply Translational Energy to Nail

Simgle impact

Multiple impacts

Solenoid

Rail gun

Push nail

                                                    

















               

In the example shown in figure 4.10, 24 combinations can be found from the concepts generated ( 4×2×3). Figures 4.11, 4.12 and 4.13 show the sketch of four possible solutions arising from the combination of concepts. The first solution, shown in figure 4.11, is due to the combination the concepts “solenoid”, “spring” and “Multiple impacts”. The second solution, shown in figure 4.12, results from the combination of “rotary motor with transmission”, “spring” and “multiple impacts”. The third, fourth and fifth solutions, shown in figure 4.13, arise from the combinations of concepts “rotary motor with transmission”, “spring” and “single impact”.

Convert Electrical Energy to Translational Energy

94

                                

It is essential to analyze very carefully each option before rejecting it. The design team must have in mind that, initially many combinations may not seem to provide a practical solution to the problem at hand, specially to the inexperienced designer.

4.4 The morphological chart

Figure 4.11: Concept 1. Solenoid compressing a spring which is then released repeatedly in order to drive the nail with multiple impacts. Adapted from Ulrich & Eppinger (2000). Convert Electrical Energy to Translational Energy

Rotary motor with transmission

Linear Motor

Accumulate Energy

Spring

Moving mass

Apply Translational Energy to Nail

Simgle impact

Multiple impacts

Solenoid

Rail gun

Push nail



              



              

Figure 4.12: Concept 2 showing a possible combination of a motor with a transmission, a spring and multiple impacts. The motor repeatedly winds and releases the spring, storing and delivering energy over several hits. Adapted from Ulrich & Eppinger (2000). c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

95

4.4 The morphological chart

4.4 The morphological chart

96

Feature Support

Convert Electrical Energy to Translational Energy

Rotary motor with transmission

Accumulate Energy

Spring

Linear Motor

Rail gun

Solenoid

Moving mass

Simgle impact

Multiple impacts













        







MOTOR

Air cushion

Slides Linear induction

Pedipulators

Driven wheels

Air thrust

Power

Electric

Petrol

Diesel

Bottled gas

Steam

Gears and shafts

Belts

Chains

Hydraulic

Flexible cable

Steering

Turning wheels

Air thrust

Rails

Stopping

Brakes

Reverse thrust

Hydraulic ram

Rack and pinion

Screw

Chain or rope hoist

Seated at rear

Standing

Walking

Transmission

Push nail

   

 

  

 


CAM

Track

Propulsion

Operator

TRIGGER

Wheels

Moving cable

Lifting

Apply Translational Energy to Nail

Means

Seated at front

Ratchet

Remote control

Figure 4.14: Morphological chart for a forklift truck, with one possible combination of sub-solutions picked out by the dashed line (After Cross, 1994). Two examples of morphological charts are presented by Cross (1994). The first one is concerned with finding alternative versions of the conventional forklift truck used for lifting and carrying loads. In the second one, alternatives for the design of a welding positioner are explorer. Regarding the finding of alternative versions of a lifting truck, the essential features of the truck are: 1. Means of support which allows movement.

Figure 4.13: Concept 3, 4 and 5 showing possible combinations of a motor with a transmission, a spring and a single impact. The motor winds a spring, accumulating potential energy which is then delivered to the nail in a single hit. Adapted from Ulrich & Eppinger (2000).

2. Means of moving the vehicle. 3. Means of steering the vehicle. 4. Means of stopping the vehicle. 5. Means of lifting loads. 6. Location of the operator. The morphological chart generated for the above functions is shown in figure 4.14 where one possible solution is highlighted. It is interesting to note that

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97

4.4 The morphological chart

4.4 The morphological chart

98

there are 90 000 possible combinations in the chart, although, some of them obviously, are not possible or include incompatible concepts. In the second example, alternatives for the design of a welding positioner, a device used to support and hold a workpiece and locating it in a suitable position are explored. Figure 4.15 shows the morphological chart for this case where several concepts are described by means of sketchs and text. One possible combination of concepts is indicated by the zig-zag line through the chart.

References

Partial Functions ENABLE connection with workpiece

ENABLE rotational movement

2

3

4

mechanical screw or bolt

wedge

sliding journal bearing

magnetic

sphere

fulcrum pin position

screw thread

straight line guidance

hold directly by hand, weight of workpiece

hang from above

lever mechanism







CONTROL of movement

hydraulic

rolling bearing

cylinder



DRIVE (by hand)

pneumatic

Rotational guidance

bearing, sliding or rolling

LOCK state

6

Force locking (friction)

Form interlocking

     

ENABLE height adjustment

5

     

ENABLE tilting movement

1







1. Altshuller, G. S. (1984) Creativity as an exact science. Gordon and Breach Science Publishers, New York, U.S.A. 2. Cross, N. (1994) Engineering Design Methods, John Wiley & Sons. 3. Otto, K. & Wood, K. (2001) Product Design - Techniques in Reverse Engineering and New Product Development, Prentice-Hall. 4. Pahl, G. and Beitz W. (2001) Engineering Design - A systematic Approach. Second Ed. Springer. 5. Ullman, D. (2001) The Mechanical Design Process. Third Ed. McGrawHill. 6. Ulrich, K. & Eppinger, S. (2000) Product Design and Development. Second Ed. Irwin McGraw-Hill.

Action Principles / Families of Function carriers

form interlocking

force locking (friction) screw screw with wedge, washer brake block

hole − pin

ratchet mechanism

within guidance

Direct

gear wheel pair

rack and pinion

helical gears (crossed)

through drive mechanism

through locking (ratchet)

optical

electronic

with mechanical advantage device

mechanical

Show position line scale

pointer scale

band, lever worm and rope, eccentric worm−wheel chain cam

mechanical stop

Figure 4.15: Morphological chart for a welding positioner, with one possible combination of sub-solutions picked out by the zig-zag line (After Cross, 1994).

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

5.0

100

Concepts

Design Brief Generation

CHAPTER

Screening and Scoring

Screening and Scoring

Development and Testing

Final Concept Testing

5

Concept Selection

In the previous chapter some methods to generate potential solutions for a design problem where reviewed. Normally, a design team should generate tens or even hundred of ideas. Clearly not all ideas will lead to a successful product. However, at this point in time, with few information at hand, it is not possible to say which concept is best. In concept selection the goal is to expend the least amount of time and resources on deciding which concepts have the best chances to become a successful product. Concept selection requires the evaluation, of concepts with respect to some criteria comparing their relative strengths and weaknesses in order to select one or more concepts for further evaluation and testing. Here, evaluation should be understood as the process of comparison and decision making. The concept selection phase usually requires at least three steps: 1. Estimate the technical feasibility of the concepts. All those concepts that are regarded as not feasible or ill-conceived are quickly discarded. 2. Concept screening. Concepts are compared roughly in relative terms against a common reference concept. Those that do not offer any advantage or fail to fulfill the requirements of the customer are discarded. 3. Concept scoring. A more detailed comparison is carried out including more information about the concepts for finer resolution. c Copyright 2004 Dr. Jos´ e CarlosMiranda. Todos los derechos reservados.

Feasibility Judgment

Generation and Screening

Figure 5.1: Concept selection is an iterative process that goes through different phases and is closely related to concept generation and concept testing.

The last to steps are usually done in an iterative fashion, where concepts are discarded and some other are combined to generate new concepts. After sufficient iterations have been carried out, the team goes to the next stage: concept testing. Figure 5.1 depicts the above procedure. The iterative behavior of the design cycle is perhaps better represented by the design-build-test cycle shown in figure 5.2. In the diagram, two different design cycles are represented by the inner and outer loops. The first loop represent the design cycle when new or complex technologies are being use. In this case, building a physical model and testing it is the only approach possible. The outer loop represent a more common approach where no physical devices are build until the very end of the process. Here, the time and expense of building physical models is eliminated by developing analytical models and simulating the concept before anything is build. All the iterations occurs without building any prototypes as all ideas are represented by means of analytical models and graphical representations, usually with the help of computers. Regardless of which design path is chosen, several benefits arises when a structured approach is followed to select concepts. Probably the most most important is that because concepts are compared against customer needs, the selected concept is likely to be focused on the customer. Other benefits may include a reduced time to product introduction and effective decision making. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

101

5.1 Estimating Technical Feasibility DESIGN

Iterate

Iterate

Build prototypes with each closer to the final product

Analytical models and graphical drawings to refine concept and product

Test physical protoypes

TEST Build final product

Figure 5.2: Design evaluation cycles. After Ullman (2003).

5.1

102

represent a problem to estimate as different people will give values that can vary by orders of magnitude.

Simulatable technology

Design prototypes

BUILD

5.1 Estimating Technical Feasibility

Estimating Technical Feasibility

When concepts are generated, members of the design team may experience feelings about the idea that can be grouped in three main reactions: 1. It will never work 2. It may work depending on something else 3. It is an idea worth considering The above judgments regarding technical feasibility are based on the experience of the design team and the individual engineers and their ability to estimate correctly. In general, it is safe to say that the more experience, the more chances the decision will be reliable at this point. Fortunately, estimating is a skill that any person can learn and cultivate to a very good degree. According to Otto and Wood (2001), the estimating skill of an engineer is dependent mainly on familiarity with dimensional units and with the different values along the dimensions. This familiarity takes place in two different levels of abstraction. First, perceived units like length or mass usually represent no problem as everyone can associate their dimensions with day-to-day experiences. On the other hand, derived units like energy or power, usually c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

What allows an engineer to become more familiar with derived dimensions is to associate them with known values. For example, one might realize that 2000W is 3hp, the common power for a lawnmower; or that 0.1MPa is 1atm, the atmospheric pressure at sea level. It is said that a skilled engineer will have at least three readily understood reference levels for every dimensional unit such as power, energy, pressure, force, acceleration, etc. Table 5.1 shows some approximated values for different units to be used as reference. The “gut feeling” reactions to the generated concepts are worth exploring since they have different implications and may induce the individual or design team to discard potentially good ideas or adapt potentially dangerous ones. It will never work. Before discarding concepts that appears to be infeasible or unworkable, consider it briefly from different points of view before reject it. As a guideline, before rejecting the concept answer the following questions: • Why it is not technologically feasible? • Does it meet the requirements of the customer? • Is the concept different from the rest? • Is the concept an original idea? To answer the first two cases, where more attention is deserved, the methods described later in this chapter will be of help. In the case of the last two, it is worth analyzing if the reaction is a product of resistance to change or the “not invented here” syndrome. It may work depending on something else. This reaction is product of a doubt in the design team due to internal or external requirement that may be judged to be either non-existent or not ready for consideration. Typical question to be made in order to get insight of this reaction are: • Is the technology needed available? • Is the technology ready for production? • Is all information needed readily available? • Is is dependent on other parts of the product? c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Energy

Mass

Force

Pressure

Acceleration

Velocity

(W)

(J)

(kg)

(N)

(MPa)

(m/s2 )

(m/s)

(m)

Ant crawling up

Moving 5g snail:

1” × 1” piece

Electrostatic attraction

Moon surface: 0.13 ×

Centripetal acceleration of

Tip speed of a wrist watch

Human hair

a wall at

0.56µJ kinetic

of paper: 40

between electron and

10−9 MPa

a regular clock hour

hour hand: 20µm/s. 10’

thickness:

1cm/s: 33µW

energy

×10−6 kg

proton in hydrogen

hand: 0.3µm/s2

snow accumulation rate

30µm

atom: 0.08µN

Length

103

10−6

Power

over 2 winter months:

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

0.1µm/s 10−3

LED: 40mW

Bee in flight:

Grape: 10g

Piece of paper, weight:

Blood pressure: 16 ×

Centripetal acceleration of

Tip speed of a wrist watch

Book cover

2 mJ kinetic

Penny: 3g

0.04N

10−3 MPa. Mars

a regular clock minute

minute hand: 1mm/s

thickness: 2mm

atmosphere: 0.8×

hand: 1 mm/s2

Speed of tide rising from

energy

10−3 MPa 1

low to high: 0.1 mm/s

Small flashlight:

A small apple

Small meal or a

Small apple, weight: 1N

10m underwater: 0.10 MPa

Fast car acceleration:

Falling body after 1/10s:

Person’s height:

10W

lifted 1m in

large snack:

Finger force for

1atm = 0.10MPa

3m/s2 . Hard braking

1m/s. Walking speed:

2m

gravity: 1J.

1kg

appliance buttons: 7N

2

Piston engine

car: 7m/s . Earth gravity

A small apple

compression pressure:

at sea level: 9.8m/s2

falling 1m: 1J

1.3 MPa

1.5m/s

kinetic energy 100

Bright light

140km/hr fast ball:

Average

Bag of potatoes, weight:

Piston engine firing

Humans black out: 40

Highway speed: 30m/s

Soccer field

bulb: 100W

114J kinetic

person:

100N

pressure: 3.5MPa

m/s2 . Belly flopping

Jetliners: 250m/s

length: 100m

Typical

energy

70kg

hard in water from a 10m diving board jump,

Statue of

causing broken bones:

Liberty: 93m

Small lawn

Energy effectively

Mid-sized car:

Two small people,

Pressure to create a

Marble dropped from 1m

3 times the speed of

Width of a small

mower

extractable

1300kg

weight: 1.5kN

diamond: 5GPa

stopping in sand,

sound: 1km/s

town: 5km

engine:

from a AA

Elephant:

Deep ocean trench:

Head-on car collision

2000W

battery: 1kJ

5000kg

0.11GPa

occupant deceleration: 10km/s2. Bullet fired

D-sized battery:

from a rifle: 60km/s2

80kJ 106

Electrical power

Car @ 130km/h:

A 747 fully

Boeing 747: 1MN

Center of the Earth: 0.40×

Projectile fired from a rail

Voyager 1 traveling in

Dallas, TX to

to a small

1 MJ kinetic

loaded:

thrust.

106 MPa

gun: 800km/s2

outer space: 17km/s

Denver, CO or

town: 1MW

109

energy

300,000kg

Boston MA to

Automotive

Ocean liner:

Pittsburgh PA:

Battery: 5MJ

107×106kg

Electrical power

USS Nimitz

Aircraft carrier:

plant: 1GW

91,400 tons @

0.5×109kg

1000km

30 knots: 9.9

Saturn V or Space

Center of the sun:

Centrifugal acceleration of

Shuttle:

20 ×109 MPa

0.2 GN thrust

Speed of light in

Earth to moon:

light trapped in a black

vacuum:

3.84×109m

hole: 2×1013m/s2

3×108m/s

GJ kinetic energy

Table 5.1: Approximate reference values on different dimensions (adapted). After Otto & Wood (2001).

5.1 Estimating Technical Feasibility

100m/s2.

100-1000W 103

Height of the

household appliance:

5.2 Concept screening 104

In the first two cases, the technology needed should be carefully examined to see if it is available and if it is already mature or can be by the time the product reach production. In the third case, serious consideration should be given to decide if it is worth waiting for more information to become available. Finally, in the last case, it should be pondered if other parts of the product could be modified to accommodate the intended design without causing a delay in the design process.

Concept screening

It is an idea worth considering. This is generally the hardest case to evaluate, since knowledge and experience are an important part for the evaluation of its feasibility. The methods described later in the chapter will help to develop a deeper knowledge about the concept in order to evaluate it.

5.2

Concept screening is a technique based on a method developed by Stuart Pugh and is also known as Pugh concept selection method (Pugh, 1990). The main idea of the technique is to narrow the number of concepts quickly comparing the concepts between themselves based on common criteria and to improve the concepts whenever possible.

Concept screening is based on the following steps:

1. Choose the criteria for comparison.

2. Choose which concepts will be evaluated.

3. Decide on a reference concept to be used as a datum.

4. Prepare the selection chart.

5. Rate the concepts.

6. Rank the concepts.

7. Combine and improve the concepts.

8. Select one or more concepts.

Step 1: Choose the criteria for comparison. To start, it is necessary to know the basis on which the different concepts will be compared with each

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105

5.2 Concept screening

other. During QFD, an effort was made to develop a set of customer requirements. This requirements are generally well suited to be used as a criteria for comparison. In some cases, when the concepts are well refined, engineering targets may be used instead. Step 2: Choose which concepts will be evaluated. After concept generation several options where available. These options where narrowed down discarding those concepts that were not technically feasible. From the options left, choose the group to be evaluated. If more than 12 concepts are to be considered, the design team can vote to select the 12 concepts that will be compared.

5.2 Concept screening

106 Concepts

Datum Selection Criteria

Concept B

Concept C

Concept D

Concept E

Concept F

Criterion 1 Criterion 2 Criterion 3 Criterion 4 Criterion 5 Criterion 6 Criterion 7

Step 3: Decide on a reference concept to be used as a datum. To select a reference concept or datum, the design team can follow several approaches. If the company already has a current product, it may serve well as a well understood concept. Other option is to use a competitive product that the team wish to superpass. Pugh (1990) recommends using as a datum the concept that the team vote best.

Sum +’s Sum 0´s Sum −’s Net Score Rank Continue?

Step 4: Prepare the selection chart. Once the criteria for comparison, the concepts that will be evaluated and the datum all have been chosen, the next step is to prepare the selection chart. For that purpose the template shown in figure 5.3 can be of help. Step 5: Rate the concepts. To rate the concepts, compare them against the datum using a very simple scale. It is recommended to use a + if the concept is better than the datum for the current criterion, a − if the concept is worse than the datum and a 0 or an S (“same”) if the concept is judged to be about the same as the datum or there is some ambivalence. If the decision matrix is carried out in a spreadsheet use +1, 0 and −1 for scoring. It is advisable to to rate every concept on one criterion before moving to the next. Step 6: Rank the concepts. After all the concepts have been rated for each one of the criterion, four scores are generated: the number of +’s, the number of −’s, the number of 0’s and the net score. The net score is obtained subtracting the number of −’s from the number of +’s. To rank the concepts, simple use the one with the best net score as 1, the next one as 2 and so forth. Step 8: Combine and improve the concepts. After the concepts have been rated and ranked, the design team should verify the validity of the results. Some recommendations for the interpretation of results are pointed out by c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Figure 5.3: Template for the Pugh selection chart. Ullman (2003): • If a concept or group of similar concepts has a good overall total score or a high + total score, it is important to notice what strengths they exhibit, that is, which criteria they meet better than the datum. Likewise, groupings of − scores will show which requirements are especially hard to meet. • If most concepts get the same score on a certain criterion, examine that criterion closely. It may be necessary to develop more knowledge in the area of the criterion in order to generate better concepts. In many occasions, concepts can be combined to improve them. Here, to help visualize if concepts can be combined, Ullrich and Eppinger suggest to answer the following questions: • Is there a generally good concept which is degraded by one bad feature? c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

107

5.2 Concept screening

5.2 Concept screening

• Can a minor modification improve the overall concept and yet preserve a distinction from the other concepts?

108

Removable Unit

Removable Chamber

Removable Blade

Washable

Scraper

Cost

0

+

_

+

0

Store Grinder

0

+

0

0 _

+ _

0

Put in Beans

+ _ _

_

0

0 _

0

+

0

• Are the two concepts which can be combined to preserve the “better than” qualities while annulling the “worse than” qualities? If any improved concepts arose from combination, these are added to the selection chart and ranked along the original concepts. Step 9: Select one or more concepts. Once the above steps have been carried out, and the design team is satisfied with their understanding of each concept, its strengths and weaknesses, it is time to decide which concepts should be selected for further refinement and analysis. The design team should also clarify if issues need to be investigated further before a final decision can be made. In addition, decisions should be made if the screening matrix has provided enough resolution and if another round of concept screening should be performed. If concept screening has not provided enough resolution, concept scoring should be applied next. la An example of a Pugh chart for the redesign of a coffee grinder is shown in figure 5.4. In this example, presented by Otto & Wood (2001), the goal was to evaluate different concepts all restricted to the use of a chopper. Several ideas were developed to improve the grinder, focusing on cleaning functions. The criteria for the redesign evaluation gathered directly from customer needs and engineering specifications are as follows: • Cost: unit manufacturing cost (development and delivery costs were not considered). Measured in $.

Selection Criteria

0 _

Take Out Coffee

0

Power Setup

0

Cleanable

0

0 _

Development Risk

0

+

0 _

Sum +’s

0

3

1

3

0

Sum 0´s

7

2

2

1

6

Sum −’s

0

2

4

3

1

Net Score

0

1

−3

0

−1

Rank

2

1

4

2

3

0

Figure 5.4: Pugh chart for coffee mill redesign concepts regarding cleanability. Adapted from Otto & Wood (2001).

• Store grinder: facility to put away in a cabinet out of sight. Measured in cm3 .

• Cleanable: Time or steps needed from the point where the coffee has been taken out until the point of being spotless. Measured in number of steps or seconds.

• Put in beans: Time elapsed between the beans are in a bag until the chopper switch can be activated. Measured in seconds.

• Development risks: Difficulty getting a working alpha prototype. Measured in number of potential faults or difficulties.

• Take out coffee: Time elapsed between removing all grounds until all the coffee is poured into a coffee maker. Measured in seconds. • Power setup: Time elapsed between the grinder is plugged in until the switch can be activated. Measured in seconds.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

From the chart some conclusions could be drawn. First, the power setup criteria does not distinguish between concepts as all of them were about the same. Therefore, although it was an important criterion for the product, it did not impact cleanability, and was dropped from further discussion. Next, the removable blade concept was clearly ahead of the rest and was a natural c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

109

5.3 Concept scoring

5.3 Concept scoring

110

candidate for further development.

5.3

Concepts

Datum

Concept scoring Selection Criteria

Concept scoring is a technique very similar to concept screening and it is used when increased resolution will better differentiate among concepts. In this method, the teams weight the relative importance of the selection criteria and focuses on more refined comparisons with respect to each criterion. The steps to use the method are as follows:

Weight

Rating

Weighted Score

B Rating

C Weighted Score

Rating

D Weighted Score

Rating

Weighted Score

Ease of use Readability of settings Ease of handling Dose metering accuracy Durability Ease of manufacture Portability Total Score Rank

1. Choose the criteria for comparison. 2. Choose which concepts will be evaluated. 3. Decide on whether only one concept will be used as a datum or, if different concepts will be used as reference for different criteria. 4. Prepare the selection chart and decide the weight for each criterion. 5. Rate the concepts. 6. Rank the concepts. 7. Combine and improve the concepts. 8. Select one or more concepts. As most of the steps are identical to the concept screening ones, only those different will be discussed next.

Continue?

Figure 5.5: Template for a concept scoring matrix.

it will be seen later. For this reason, many times different concepts are used as reference for different criteria. Step 4: Prepare the selection chart and decide the weight for each criterion. The selection charts for the scoring method is very similar to Pugh charts with two exceptions. First, for each criterion, it includes its weight. Second, the chart includes two columns per concept: rating and weighted score. A template for an scoring chart is shown in figure 5.5. The weight for each criterion is usually defined as the percentage of importance that the criterion has relative to the other criteria. Each percentage is defined such that the sum of all different percentages is 100%. An example illustrating the use of weights is shown in figure 5.6 where three different cars are compared in base to four different criteria: fuel consumption, cost of spare parts, simplicity of servicing and comfort. Each criterion has its own weight defined by some chosen rules: fuel consumption weight is 50%, the cost of spare parts has a weight of 20%, easy to maintain 10% and finally, comfort 10%. It is easy to see in this example that the sum of all weights is 100%.

Step 3: Decide on whether only one concept will be used as a datum or if different concepts will be used as reference for different criteria. Although a single reference concept can be used for the comparative ratings of all criteria as in the screening method, this is not always appropriate. Unless by pure coincidence the reference concept is of average performance relative to all criteria, the use of the same reference concept for the evaluation of each criterion may lead to what is known as the “scale compression effect”. Consider, for example, that the reference concept to be used as datum is better than the rest in 1 criterion. If this is the case, all the concepts could be evaluated only as “same as” or “worse than”, effectively compressing the evaluation scale to 2/3. This effect applies independently of the scale used, as

In many ocassions, the selection of the right weighting factors can be a cumbersome task, specially if many different criteria have to be taken into account. One alternative is to use a objectives tree that includes weighting for each criterion. To show how objectives trees are constructed, consider the objective

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c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

111

5.3 Concept scoring

Car A Selection Criteria

Weight

Parameter

Low fuel consumption

50%

Miles per galon

Low cost of spare parts

20%

Easy to maintain High comfort

Value

Car B

Rating Score

Value

1

Rating Score

Value

1.0

Rating Score

2

1.0

40

4

2.0

36

3

1.5

Cost of 5 typical parts

£18

7

1.4

£22

5

1.0

£28

2

0.4

10%

Simplicity of servicing

Very simple

5

0.5

Com− plicated

2

0.2

Average

3

0.3

20%

Comfort rating

Poor

2

0.4

Very good

5

1.0

Good

4

0.8

Rank

112

Car C

33

Total Score

5.3 Concept scoring

3.3

4.2

3.0

2

1

3

11

12

13

0.25 0.25

0.60 0.60

0.15 0.15

Figure 5.6: Scoring matrix for three alternative motorcars. Adapted from Cross (1994).

tree in figure 5.7. Each criterion in the objectives tree is represented by a circle or box with three numbers on it. At the top of each box, a number represents the level of the criterion. For example, the set of criteria is level 1, representing a weight of 100% or 1. If there are three main criteria, then the first would be represented by the number 11, the second by the number 12, the third by the number 13, an so on. If the second criterion, number 12 has two criterions that must be considered, then the first one will be identified by the number 121 and the second one by the number 122. If the criterion identified by the number 121 has to be divided into two different criteria, then the first would be 1211 and the second one 1212. The objectives three can have as many levels as necessary. The second number, at the lower left side of the box, indicates the weight of the factor to whom it belongs. The third number, at the lower right end, is result of the multiplication of the weight of the criterion times the weight factor of its parent box. This product gives the contribution of the criterion to the total 100%.

1.0

1.0 = 0.25

121

122

131

132

0.75 0.45

0.25 0.15

0.30 0.05

0.70 0.11

1211

1212

0.50 0.22

0.50 0.22

+ 0.22

+

0.22

+ 0.15

+

0.05

+

0.11

Figure 5.7: An objetive tree with weighting factors.

for 0.25, mechanical behavior for 0.60 and cost of manufacturing for 0.15.

This procedure is better explained through an example. The above objectives tree was constructed to aid in the selection of weighting factors for the selection of a mechanical component. The main factors for the selection of the component were specified as how safe the component was (criterion 11), its mechanical behaviour (criterion 12) and and its cost of manufacturing (criterion 13). Since these three factors must add 100%, or 1 for short, then 1.0 have to be divided between these factors. It was decided that safety accounted

Mechanical behavior was divided in two criteria, first, strenght (121) which accounted for 0.75 of the original 0.60 specified for mechanical behavior, and second, freedom from resonance (122) which accounted for 0.25 of the original 0.60. It is important to stress at this point that the sum of weights of factors which have the same parent and are at the same level must be 1.0 or 100% (here 0.75 + 0.25 = 1.0). It was considered to divided strenght further into two more specific criteria, both with the same weight, stiffness (1211) and maximum allowable stress in the component (1212). Carrying out the products, the final weight for stiffness is 0.22, which is the same value for the maximum stress criterion.

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c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

113

5.3 Concept scoring CONCEPTS

TEST RIG BOTTOM−RIGHT HINGE SCORING MATRIX Selection Criteria

Weight

Safety

0.25

Stiffness

0.22

Max. allowable stress

0.22

Freedom from resonance

5.3 Concept scoring

B

Reference Rating

Weighted Score

Rating

C Weighted Score

D Weighted Score

Rating

Rating

Weighted Score

0.15

Cost of tooling

0.05

Cost of materials

0.11

Do Nothing

Renuzit Air Freshner

Rating Score

Rating Score

Selection Criteria

Weight

Performance (olfactory distance − ft)

50%

0

Cost

25%

Ease of replacement

13% 12%

Frequency of Replacement

Total Score Rank

114

Baking Soda

Cedar Chips

Rating

Score

Rating

Vented Walls

Score

Rating

Activated Carbon

Score

Rating

Score

0

70

35

70

35

80

40

20

10

90

45

100

25

52

13

76

19

84

21

100

25

20

5

100

12.5

70

9

90

11

40

5

100

13

20

3

100

12.5

0

0

50

6

67

8

100

13

67

8

Total Score

50

57

71

74

61

61

Rank

6

5

2

1

3

4

Continue?

Figure 5.8: An objetive tree with weighting factors. Finally, the cost of manufacturing was divided into two more specific costs: cost of tooling (131) and cost of materials (132). Cost of tooling had a weight of 0.30 whereas the cost of materials had a weight of 0.70. Hence, cost of tooling final weight is 0.05 and the final weight for cost of materials is 0.11. As final observation about objectives trees, it is important to notice that the sum of weights of each level is always 1 as shown in figure 5.7 for the final level. In figure 5.8 the final template for the scoring matrix for this problem is presented. Step 5: Rate the concepts. Similar to the procedure followed in the screening method, here each concept is rated using a simple comparative scale. As more detail is needed, a more detailed rating scale is generally used. A common option is to use a 5 levels scale:

Relative performance

Rating

Much worse than reference

1

Worse than reference

2

Same as reference

3

Better than reference

4

Much better than reference

5

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Figure 5.9: Concept scoring matrix for the selection of odor control alternatives. Adapted from Otto & Wood (2001).

Sometimes a 10 or more levels scale is used, but its use is discouraged as it requires more time and effort. For example, figure 5.10 presents a scoring matrix for an outpatient syringe where four different concepts are been evaluated. Note that in this example a 5 levels scale is being used and that different concepts serve as datum for different criteria. This example is different from the one presented in figure 5.6 where a 10 levels scale is used. Step 6: Rank the concepts. Once the ratings have been specified for each criterion, the weighted score is obtained multiplying the rating for the weight of the criteria. The total score for each concepts is simply the sum of all weighted scores. Finally, each concept is given a rank corresponding to its total score. Another example showing a more elaborated scoring matrix is presented by Otto & Wood (2001). The matrix, shown in figure 5.9, helped the design team to evaluate between different alternatives to control the odors in a cat litter box. The careful reader should notice that the rating scale used in this example goes from 0 to 100, which at first sight may look unnecessary. Nevertheless, in this case a 0-100 scale was chosen as the team had high-quality information about the relative performance of each concept regarding each one of the criteria. This high-quality information is usually gathered directly from testing and experimentation, and it is not influenced by the opinion of the design team members. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

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5.4

5.4 Concept Testing

Concept Testing

5.4 Concept Testing

116

• Which of several alternatives should be pursued? • How the concept may be improved to better meet customer needs?

In the concept selection process, it is very likely that some form of customer’s response will be needed in order to further discuss the possibilities of the proposed concepts. In order to communicate the idea of the concept and to measure the response of the customer, in some cases simple verbal descriptions or drawings will suffice. In other cases, there is no other choice but to create physical prototypes of the product. This testing will give a better idea on the feasibility of the concepts and the sales potential of the product. Concept testing is carried out to facilitate decision-making during final concept selection stages, generally after some detailed design has been done. Concept testing is not necessary when: • time required to test the concept is large relatively to the product life cycle. • cost of testing is large relative to the cost of actually launching the product. Ulrich & Eppinger (2000) presents a 6 steps methodology for testing product concepts:

• Approximately how many units are likely to be sold? • Should development be continued? 5.4.2. Choosing a survey It is necessary to define the number of possible population customers to survey and in what market segments they will be. This selection is carried out in a similar fashion as the selection of customers in the “Identifying customer needs phase”. It is important, however, to have in mind that concept testing is a much more expensive activity. The most important question to answer is how large the survey population should be. Some useful guidelines are outlined next. Factors favoring a smaller sample size: • Test occurs early in the concept development process. • Test is primarly intended to gather qualitative data. • Surveying potential customers is relatively costly in time and money.

1. Definition of the purpose of the concept test. 2. Choosing of a survey population. 3. Choosing of a survey format.

• Required investment to develop and launch the product is relatively small. • A relatively large fraction of the target market is expected to value the product.

4. Communication of the concept. 5. Measurement of customer response. 6. Interpretation of results. In this initial step, the design team should clarify what questions they want to answer with the test. It is essential to define what the test or experiment is for. Some typical questions are: 5.4.1. Concept testing purpose

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Factors favoring a larger sample size: • Test occurs later in the concept development process. • Test is primarily intended to assess demand quantitatively. • Surveying customers is relatively fast and inexpensive. • Required investment to develop and launch the product is relatively high. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

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5.4 Concept Testing

• A relatively small fraction of the target market is expected to value the product. Concept tests can be done in the early stages of the development process to solicit feedback on the basic concept. 5.4.3. Choosing a survey The following formats are commonly used in conformat cept testing:

5.4 Concept Testing

118

Most concept test surveys first communicate the product concept and then measure customer response. Although is good practice to include questions to measure customer response to product concepts, in many occasions concept test generally attempt to measure purchase intent. A useful scale to measure purchase intent may be:

5.4.5. Measure customer response

• Definitely would buy

• face-to-face interaction

• Probably would buy

• telephone

• Might or might not buy

• postal mail

• Probably would not buy

• electronic mail

• Definitely would not buy

• internet It is important to realize that each of these formats presents risks of sample bias. The way in which the concept will be surveyed, is closely related to the way in which the concept will be communicated. Communication of the concept can be carried out by the following means:

5.4.6. Interpreting results Usually interpretation is straightforward if the design team is just comparing two or more concepts. It is important, though, to be sure that customers understood the key differences among concepts.

5.4.4. Communicating the concept

• verbal descriptions • sketch • photos and renderings • storyboard • video

References 1. Cross, N. (1994) Engineering Design Methods, John Wiley & Sons. 2. Otto, K. & Wood, K. (2001) Product Design - Techniques in Reverse Engineering and New Product Development, Prentice-Hall. 3. Pugh, S. (1990) Total Design, Addison Wesley. 4. Ullman, D. (2003) The Mechanical Design Process, Third Edition. McGrawHill. 5. Ulrich, K. & Eppinger, S. (2000) Product Design and Development. Irwin McGraw-Hill.

• simulation • interactive multimedia • physical appearance models • working prototypes c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

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5.4 Concept Testing

CHAPTER Embodiment design

Concepts

Selection Criteria

Weight

A

B

C

D

Master Cylinder

Lever Stop

Swash Ring

Dial Screw

Rating

Weighted Score

5%

3

0.15

Readability of settings

15%

3

Ease of handling

10%

2

Dose metering accuracy

25%

Durability

Rating

Weighted Score

Rating

Weighted Score

Rating

Weighted Score

3

0.15

4

0.2

4

0.2

0.45

4

0.6

4

0.6

3

0.45

0.2

3

0.3

5

0.5

5

0.5

3

0.75

3

0.75

2

0.5

3

0.75

15%

2

0.3

5

0.75

4

0.6

3

0.45

Ease of manufacture

20%

3

0.6

3

0.6

2

0.4

2

0.4

Portability

10%

3

0.3

3

0.3

3

0.3

3

0.3

Ease of use

6

Total Score

2.75

3.45

3.10

Rank

4

1

2

3.05 3

Continue?

No

Develop

No

No

Figure 5.10: Concept scoring matrix for an outpatient syringe. The reference points for each criterion are signified by bold rating values. Adapted from Ulrich & Eppinger (2000).

As a design task, concept embodiment is perhaps the one that is most identified with engineers as in this phase of the design process the choice of components, interfaces, materials, dimensions, shapes, tolerances, surface finishes, union methods, manufacturing and assembly processes, etc., are carried out. In order to make wise choices, engineers should be able to understand throughly the design, its functionality, objectives and constraints. Is in this stage where engineers apply their skills in mathematics and basic science. Regardless of size, complexity or cost, products must be effectively modeled, tested and, whenever possible, refined. Methods for concept embodiment must aid in this process.

6.1

Product Architecture

Product architecture is the the definition of the layout of systems, sub-systems and components according to their functional purposes. This definition of the layout of the product must also deal with what interfaces are necessary between components, sub-systems and systems. Product architecture allows the design to be divided so building blocks can be assigned to individuals, teams or suppliers in order to permit parallel detailed design, testing and refinement. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

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6.1 Product Architecture Product Architecture for the Product and Common Derivatives

Product Architecture Product

Type Integral

Modular

6.1 Product Architecture

Derivatives

Type

Fisted vegetable peeler

Fixed unsharing

Shares no common components

Wooden pencil

#1, #3 lead pencils

Modular platform

Differing lead hardness

Kitchen knife

Kitchen knife set

Modular platform

Parametric handle size

Swiss Army Knife

Complex knives

Modular platform

Expanding width

PC computer

More RAM, devices

Adjustable for purchase

Standard interfaces

Black and Decker cordless

VersaPak line of power

drill

tools

Tinkertoys

Theme sets

Modular platform Adjustable for use

Cons

Pros

Characteristics

Handheld vegetable peeler

122

Improves device reconfigurability

May make devices look too similar

Increases the device variety and speed of

Makes imitation of device easier by competitors

introduction for new devices Modular architecture

Improves maintainability and serviceability

Reduces device performance

of device Decouples development tasks (and

Common battery

manufacturing to some extent)

Modular design may be more expensive than integral design

Common motor Standard interfaces Component variety

Integral architecture

Figure 6.1: Product architecture examples. After Otto & Wood (2001).

Harder for competitors to copy design

Hinders change of design in production

Tighter coupling of team with less interface

Reduces the variety of devices that can be

problems

produced

Increases system performance Possible reduction in system cost

Product architecture is also related what is called portfolio architecture. Portfolio Architecture relates to a group or family of products, where design strategy revolves around how to share components or subsystems across products in the portfolio. Figure 6.1 shows some examples of product and portfolio architecture. In general terms, product architecture can be divided in two main types: integral architecture and modular architecture. Each type has its own advantages and disadvantages as shown in figure 6.2.

6.1.1. Types of product architecture

A product has an integral architecture when no attempt is made to divide functions into components or systems resulting in on a very small number of physical elements carrying out all functions of the product. Integral architecture is common for high-volume products where cost is not reduced through sharing components but through easiness of assembly. This results in products with fewer components but much function sharing. Modular product architecture is the result of dividing product functions into a similar number of blocks or modules that perform a limited set of functions. Ideally, a one-to-one correspondence between modules and functions is achieved. In practice, modularity is not strict, and generally speaking, products are neither fully modular or fully integral. Rather, a given product will present more or less modularity than another comparative product.

Figure 6.2: Comparison of modular and integral architectures. After Otto & Wood (2001). types: slot, bus and sectional. These three types, shown in figure 6.3, are explained next. Slot-modular architecture. Each of the interfaces between modules in a slot-modular architecture is of a different type from the others, so that the various modules in the product cannot be interchanged. An example of this type of architecture are products that are to be assembled by the customer and are constructed in such a way that any given module can fit in only one place. Bus-modular architecture. In a bus-modular architecture, there is a common bus to which the other modules connect via the same type of interface. An example of bus-modular architecture are the floppy drive, DVD, CDRW and battery that connects to a bay in a laptop using the same interface. Sectional-modular architecture. In a sectional-modular architecture, all interfaces are of the same type, but there is no single element to which all the other modules attach. The assembly is built up by connecting the modules each other via identical interfaces. An example may be modular office furniture that can be arrange in different ways depending on the modules used.

According to Ulrich (1995), modular architecture can be classified in three

Slot-modular architectures are the most common type of modular architecture because for most products, different modules require different interfaces to

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6.1 Product Architecture

6.1 Product Architecture

124

Product variety

Slot−Modular Architecture

Bus−Modular Architecture

Sectional−Modular Architecture

Figure 6.3: Three types of modular architectures. After Ulrich & Eppinger (2000) accommodate unique interactions with the rest of the system. Even when the architecture of a product is initially defined, at least informally, since the concept generation stage, formal decisions are made during the embodiment design phase. Product architecture is one of the development decisions that plays a major impact in the ability to deliver a variety of products with standard components that allows better product performance, manufacturability and maintenance.

6.1.2. Implications of the architecture

Product variety refers to the amount of different products that any given company can manufacture over a period of time. Product variety generally respond to market needs, as consumers want distinctive products. Product architecture can help to achieve a large product variety for a minimum overhead in its cost. An example is Swatch watches, where hundreds of different combinations can be achieved choosing different components during assembly. Component standardization Component standardization is the use of the same components or modules in multiple products. This standardization allows the manufacturer to minimize cost and increase quality through the production of larger volumes and the refined design of such common components. An example are cars within same or sister companies that share many parts and subsystems. Product Performance

Product change Modules are the building blocks of the product and the architecture defines how this blocks relate to the function of the product and how the blocks interact with each other. If each module is responsible for certain isolated functions, it would be possible to replace or change any given module without affecting the rest of the product. The contrary is true for an integral architecture, where changing one part of the product may have an influence in the functions carried out by the rest of it. Some of the motives for product change are: • Upgrades • Add-ons • Adaptation • Wear • Consumption • Flexibility in use and reuse. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Product performance is related to how well the final product meets customer requirements in terms of intended functions. Some examples of typical performance measures are speed, acceleration, efficiency, life, accuracy and noise. Here, architecture can facilitate the optimization of performance characteristics by means of integration and function sharing. Function sharing refers to the implementation of multiple functions through a single module or component. Function sharing can help to optimize a design, but trade offs in the advantages of modular architecture have to be considered by the design team. Manufacturability As discussed above, product architecture can influence the manufacturing cost through product variety and component standardization. In addition, many decisions regarding the architecture of a product influence the easiness of manufacturing as many complicated modules can be produced in larger volumes to reduce cost or many functions can be implemented in a single module to reduce either parts or manufacturing operations. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

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6.1 Product Architecture

Due to the importance of product architecture in subsequent steps of the product design process, it should be throughly discussed by the team design and established in a cross-functional fashion. At the end of this step, an approximate geometric layout of the product, description of the major modules and documentation about the interaction between modules should be obtained. Ulrich & Eppinger (2000) suggest to follow a four steps approach that will be illustrated using a DeskJet printer as an example. The four recommended steps are:

6.1 Product Architecture

126

6.1.3. Establishing the architecture

1. 2. 3. 4.

Create a schematic of the product. Cluster the elements of the schematic. Create a rough geometric layout. Identify the fundamental and incidental interactions.

Step 1: Create a schematic of the product. A schematic is a diagram showing the constituent elements of a product as understood by the design team. It is important that the schematic reflects the best understanding of the team, although great detail is not necessary at this step. For the purpose of establishing product architecture, some authors recommend to aim for fewer than 30 elements in the schematic. It also should be realized that there is not a unique schematic for any given product, so the team should generate several alternatives to select from. In figure 6.4 The schematic for a DeskJet printer is shown. Many elements in the schematic represent physical components such as the print cartridge, while other elements represent functional elements such as store output. Functional elements are those that have not yet been reduced to physical concepts or components, requiring further discussion by the design team in order to achieve a final decision about how they will be implemented. On the other hand, components that have been reduced to physical components are generally those that are central to the basic product concept that the team has generated and selected. Step 2: Cluster the elements of the schematic. In this step, the objective is to assign the different elements in the schematic into specific modules. As in the previous step, the assignment of elements into modules is not unique, and the design team will be faced with different viable alternatives that can range from the few to the hundreds. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Enclose Printer Print Cartridge Provide Structural Support Position Cartridge in X−Axis

Store Output

Accept User Inputs

Display Status

Position Paper in Y−Axis Control Printer

Store Blank Paper

Flow of forces or energy Flow of material

"Pick" Paper

Supply DC Power

Communicate with Host

Command Printer

Flow of signals or data Connect to Host

Figure 6.4: Schematic of the DeskJet printer. Note the presence of both functional elements (e.g., “Store Output”) and physical elements (e.g., “Print Cartridge”). For clarity, not all connections among elements are shown. After Ulrich & Eppinger (2000)

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127

6.1 Product Architecture

6.1 Product Architecture

128

One method to manage such complexity is for each element to be assigned to its own module and then to cluster elements when advantageous. Some factors worth considering when clustering elements are: Enclosure

• Geometric integration and precision. In some cases, it is convenient to cluster elements that control certain functions that are related between themselves. Elements requiring precise location or close geometric integration can often be best designed if they are part of the same module. In the case of the DeskJet, this principle would suggest clustering the elements associated with positioning the cartridge and the paper.

Enclose Printer Print Cartridge Provide Structural Support

User Interface Board Position Cartridge in X−Axis

Chassis

Store Output

Accept User Inputs

Position Paper in Y−Axis Control Printer

Store Blank Paper Paper Tray

Flow of forces or energy Flow of material

Display Status

"Pick" Paper

Power Cord and "Brick" Supply DC Power

Print Mechanism

Communicate with Host

Flow of signals or data Connect to Host

Command Printer Host Driver Software

Logic Board

Figure 6.5: Clustering the elements into modules. Nine modules make up this proposed architecture for the DeskJet printer. After Ulrich & Eppinger (2000)

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

• Function sharing. When a single device can implement several different functions, it is best to cluster the related components together. For the DeskJet it was believed that that the status display and the user controls could be incorporated into the same component. • Capability of vendors. If a specific vendor is know for its capacity in developing and manufacturing certain components, it is best if those components are cluster together. This will help the vendor to integrate more efficiently the said components. • Similarity of design or production technology. When two or more components are designed or manufactured using the same or similar technology is best to cluster them in order to save costs. An typical example of the application of this principle is the clustering of several electronic devices into a single circuit board. • Localization and change. If the design team anticipates that a component will suffer several changes over time, it is best to isolate that component into its own module. In the case of the DeskJet, the engineers decided that the printer would suffer cosmetic shape modifications and decided to isolate the enclosure into its own module. • Accommodate variety. If some components of the product will be changed to satisfy different market or operative conditions, it is best to isolate these components in a module that can be easily replaced. For the Deskjet, the engineers decided to isolate the components associated with the DC power supply as the printer was going to be sold in different parts of the world with different power standards. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

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6.1 Product Architecture

6.1 Product Architecture

• Enabling standardization. When a component or components can be used in different products, it is best to isolated them in separate module or modules. This allows the higher production of the elements in the module. An example of this standardization is the printer cartridge in the DeskJet printer.

Step 3: Create a rough geometric layout. The next step once the general components have been arranged in modules, is to generate a general geometric layout to analyze if the proposed distribution is physically possible. This rough sketch can be made out of foam or cardboard, or even as a rough 3-D computer model, as it is not necessary to include great detail. Nevertheless, it should be sufficient to decide whether component and interface distributions are possible. An example of a geometric layout for the DeskJet printer is shown in figure 6.6. In this example, the design team realized that there was a trade off between the height of the machine and how much paper could be stored in the paper tray. In many cases, the design team may decide that the geometric layout or the clustering chosen are not feasible. In this cases, components may be assigned to different modules. Step 4: Identify the fundamental and incidental interactions.

User interface board

Logic board print cartridge

Paper tray

Print mechanism

Chassis

Enclosure

Logic board

• Portability of the interfaces. Some interactions are more easily transmitted over large distances than others. For example, it is easier to transmit electric or light signals over a distance than mechanical forces and motions. It is also true for the transmission of fluid connections. As a result, it is easier to separate elements with electronic and fluid interactions. In the case of the DeskJet, the flexibility of electrical interactions allowed the design team to cluster control and communication functions into the same chunk. On the other hand, the design team was constrained by the geometric and mechanical interactions of the paper handling mechanism.

130

Print cartridge Roller/guide Paper Paper tray Chassis

Figure 6.6: Geometric layout of the printer. After Ulrich & Eppinger (2000)

According to Ulrich & Eppinger (2000) there are two types of interactions between modules. First, fundamental interactions are those corresponding to the lines on the schematic that connect the chunks to one another (see Figure 6.4). This interaction is planned and is fundamental to the operation of the system. Second, incidental interactions, are those that arise because of particular geometric or physical implementation of modules. In the Deskjet example, the vibration from the actuator in the paper tray could interfere with the precise location of the print cartridge in the x−axis.

It is common practice to divide the design so each module can be assigned to an specific person or team. Since the different modules interact in one way or another, different persons or teams have to constantly coordinate their activities and exchange information. To facilitate this interaction, interactions between modules have to be identified.

Even when the principal interaction between modules were described in the schematic, incidental ones should be documented apart. When the system includes a reasonable small number of incidental interactions (less than 10),

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6.1 Product Architecture

6.2

User Interface Board

Enclosure

Styling

Paper Tray

Vibration

Print Mechanism

Thermal Distortion RF Shielding

Chassis

Thermal Distortion

Logic Board

Host Driver Software

RF Interference

Power Cord and "Brick"

Figure 6.7: Incidental interaction graph. After Ulrich & Eppinger (2000) an incidental interaction graph is convenient. Figure 6.7 shows an example of an interaction graph regarding the DeskJet example. This graph shows that vibration and thermal distortion are two incidental interactions that may affect the performance of the print mechanism. The design team should be careful to address these issues. To define the interactions between modules, flows in material, energy and signals must be investigated and refined at each module boundary. These flows usually define the interactions and the boundaries define the interfaces. According to Cutherell (1996), four types of interactions are typically investigated:

1. Material interactions: solid, liquids, or gases that flow from one module to the next. 2. Energy interactions: energies that must be transmitted or shielded between modules. 3. Information interactions: signals (tactile, acoustic, electrical, visual, etc.) that must be processed from one module to the next, and 4. Spatial interactions: geometrical dimensions, degrees-of-freedom, tolerances, and constraints that must be maintained between modules. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

6.2 Geometry and layout refinement

132

Geometry and layout refinement

In the quest of creating a robust product, two main activities take place once rough concepts have been generated and selected: 1. refining the geometry and architecture of the product, 2. systems modeling toward detail design. Take for example the electric wok presented by Otto & Wood (2001) shown in figure 6.8. In this case the design team was faced with the task of improving an existing product. As shown, the original concept of the wok evolved to a new one that included more advanced controls and configurations accommodating improved product cleaning and storage. As a result of the embodiment design phase, components, parts, assemblies and interfaces were clearly defined, from both geometrical, and functional points of view. Another example of the result of embodiment design is shown in figure 6.9, where an exploded view of the PrestoTM hot air popcorn popper is shown. In any case, the embodiment process include the following tangible documentation: • • • • • • • • •

detailed drawings, exploded views, assembly diagrams, tool designing, manufacturing process plans, tolerance design, packaging, maintenance and warranty information and user’s manual.

In order to generate the above documentation, some guidelines described next may be followed. The main objective of these guidelines is to transform a concept sketch into refined geometry and material choices focusing on the functional performance of the product, including all relevant engineering specifications. c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

133

6.2 Geometry and layout refinement

6.2 Geometry and layout refinement

134

Figure 6.8: Embodiment example of a new electric wok concept. (a) Original wok concept. (b) Original product realization. (c) Evolved wok concept. (d) Realization of new product concept. After Otto & Wood (2001) In the embodiment design phase, specific layouts and parameters are generated in order to logically chose a given concept from a number of solution alternatives that have been developed. Ideally, the result of this phase is a single developed concept, in its definitive form, for the product or each subsystem defined including: • • • •

geometric layout material composition quality and manufacturability issues economics

In practice, the design team may be faced with the situation that further refinement of the selected concepts is needed before commitment for a single solution occurs.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Figure 6.9: Embodiment example of the PrestoTM hot air popcorn popper. After Otto & Wood (2001)

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135

6.2 Geometry and layout refinement

6.2 Geometry and layout refinement

136

Prepare parts lists (BOM), assembly drawings, part drawings, product process plans Develop possible layouts for supporting functions

4. Definitive Layout

Check for robustness and errors Inventory required supporting functionality

Engineer the dimensions of components

In order to deal with these complex characteristics of embodiment design, Pahl & Beitz (1996) suggest a general process to iteratively refine the geometry and layout of a product from an abstract form to a well-defined one. Figure 6.10 illustrates this general process.

3. Preliminary Layout

Evaluate against customer, technical, robust, safety, and business case criteria

Without doubt, the main challenge of embodiment design is that when parameters in the different subsystems or modules change, they usually affect other subsystems or modules, they propagate. This behavior is the result of having parameters that are highly coupled between product subsystems/modules. This scenario means that embodiment design activities of the different subsystems/modules must be carried out simultaneously and iteratively. As one change is made, its effects in the other subsystems/modules are studied and, if acceptable, the change is approved and its effects mitigated. The process stop when the performance of the product becomes acceptable.

Complete form design with detailed drawings

In this situation, parallel development of the concepts should be carried out. It is important to try to select one final concept as soon as possible in order to direct more resources for the development of the final product.

• • • •

maximum/minimum dimensions of the product clearance between relative subsystems/modules installation paths general arrangement of components relative to one another.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

Select an effective layout

Fill in the spatial form with scale drawings

2. Concept Layout

Select and effective layout for module placement

Develop preliminary layouts possibilities for the module placement

Identify the main functional modules

Define the spatial form with preliminary scale drawings

After critical specifications have been selected, the next step is to draw a scale sketches of the product. These sketches should have enough detail to incorporate all critical aspects of the alternatives but care should be taken to avoid over-constraining the models. These drawings includes the following items:

Using the engineering specifications, identify crucial requirements

• size and geometric specifications • material specifications • arrangement specifications

1. Concept

The process begins defining customer needs and the engineering specifications that fulfill them. Critical specifications/requirements that will drive the embodiment process are identified. Some examples of critical specifications are:

Figure 6.10: A general process for concept embodiment. After Pahl & Beitz (1996)

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137

6.2 Geometry and layout refinement

Once the sketches have been completed, it should be verify that each product subsystem, module, part or assembly fulfills its intended function completely. Also, the different sketches should be checked for possible geometry simplifications and function sharing.

6.2 Geometry and layout refinement Embodiment

Checklist issue

Function

Are the customer needs satisfied, as measured by the target values?

138

Is the stipulated product architecture and function(s) fulfilled? What auxiliary or supporting functions are needed? Working principles Do the chosen form solutions (architecture and components per function) produce the desired effects and advantages?

Based on the results, alternative sketches should be generated if needed. Next, ranges of geometric, materials, and other variables should be established and listed for each subsystem/module. Also, decisions regarding the possible use of standard components in each subsystem/module should be made. This process stage is finished by choosing between alternative layouts using the product specifications. The scale drawings are updated with the choices made.

What disturbing noise factors may be expected? What byproducts may be expected? Layout, geometry

Do the chosen layout, component shapes, materials, and dimensions provide

and materials

minimal performance variance to noise (robustness), adequate durability (strength), efficient material usage (strength-to-mass ratio), suitable life (fatigue), permissible deformation (stiffness), adequate force flows (interfaces and strength concentrations),

As the next stage, additional functions that may be needed to carry out support and auxiliary requirements should be identified. Then, rough layouts for these additional functions should be developed ensuring the compatibility of all subassembly interfaces. This task usually requires the use of standards, mathematical models, design guidelines and experimentation in order to determine all appropriate parameters. At the same time, the product should be evaluated against customer, technical, robust, safety an economic criteria and the layout should be checked to estimate potential faults. The embodiment process concludes with the testing of physical prototypes and the design of appropriate tooling.

adequate stability, impact resistance, freedom from resonance, unimpeded expansion and heat transfer, and acceptable corrosion and wear with the stipulated service life and loads? Energy and

Do the chosen layout and components provide

kinematics

efficient transfer of energy (efficiency), adequate transient and steady state behavior (dynamics and control across energy domains), and appropriate motion, velocity and acceleration profiles?

Safety

Have all of the factors affecting the safety of the user, components, function, operation, and the

Ergonomics

Have the human-machine relationships been fully considered?

environment been taken into account? Have unnecessary human stress or injurious factors been predicted and avoided? Has attention been paid to aesthetics and economic analysis of the production process, capability, and suppliers?

A second method to supplement the general embodiment process, is the application of the embodiment checklist developed by Pahl & Beitz shown in table 6.1. This table provides a systematic approach to apply proven design principles during the embodiment phase. The objective of the list is to ensure robustness, clarity, simplicity and safety in a product.

6.2.1. Embodiment checklist

The checklist involves categories of possible engineering specifications, where each category has a set of basic questions that should be exhaustively applied to the product and the different subsystems/modules as they are being detailed. It should be noted that mathematical models or physical prototypes may be needed to effectively answer each of the questions.

Quality control

Have standard product tolerances been chosen (not too tight)?

Assembly

Can all internal and external assembly operations be performed simply, repeatedly, an in the

Have the necessary quality checks been chosen (type, measurements, and time)? correct order (without ambiguity)? Can components be combined (minimize part count) without affecting modular architectures and functional independence of the product? Transport

Have the internal and external transport conditions and risks been identified and solved?

Operation

Have all of the factors influencing the product’s operation, such as noise,

Life cycle

Can the product, its components, its packaging be reused or recycled?

Have the required packaging and dunnage been designed? vibration, and handling been considered? Have the materials been chosen and clumped to aid recycling? Is the product easily disassembled? Maintenance

Can maintenance, inspection, repair, and overhaul be easily performed and checked?

Costs

Have the stipulated cost limits been observed?

Schedules

Can the delivery dates be met, including tooling?

What features have been added to the product to aid in maintenance? Will additional operational or subsidiary costs arise? What design modifications might reduce cycle time and improve delivery?

Table 6.1: Checklist for embodying a product concept. Adapted from Pahl & Beitz (1996). c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

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6.3

6.3 Trends for the design process

Trends for the design process

6.3 Trends for the design process

Market

Specifications

140

Concept Design

Detail Design

Manufacture

Sell

Iterations

In the last decades technology has brought profound changes in the way engineers design. Computational tools together with methods to increase the communication with all parts involved in the life cycle of a product have shortened significantly the amount of time needed to put a initial concept or idea into the market as a final product. From all the techniques that are or have been applied, concurrent engineering and computer aided tools have been most significant. 6.3.1. Concurrent Traditionally, design, manufacturing and marketing acengineering tivities have taken place sequentially rather than concurrently or simultaneously. The designer team would spend large amounts of time analyzing components and preparing detail drawings for a new product. After the design was considered satisfactory, the design team forwarded the information to the manufacturing team who would, once more, spend large amounts of time figuring out how to manufacture the product according to design specifications. After facilities and manufacturing processes were ready for production, the marketing team began to prepare a marketing strategy based on the product features. Although may seem logical at first, this linear scheme proved to be inadequate. In many occasions the design team ended up with a product that was difficult to manufacture and even difficult to sell. Great efforts were wasted (and sometimes still are) doing re-designs to improve manufacturing and to add features to improve the marketing of the product. To avoid the previous problems it is best to include members of the manufacturing and marketing divisions into the design team from the conceptual stages of the design process. The inclusion of the members will help to achieve a better decisions to avoid design features that are difficult to manufacture or no desirable from the marketing point of view. This approach, that may also include members from other areas like distribution and disposal, is called Concurrent Engineering.

Figure 6.11: Depiction of concurrent engineering in the design process. After Pugh (1991).

Life cycle means that all aspect of the product, such as design, development, production, distribution, use, disposal, and recycling, are considered simultaneously. The basic goals of concurrent engineering are to reduce changes in a product’s design and engineering to reduce the time and costs involved in taking the product from its design concept to its production and its introduction into the marketplace. Figure 6.11 shows a simple design process models that makes emphasis in the interaction between phases due to the use of concurrent engineering principles. As discussed above, while designing a product, several disciplines must be taken into account. One of those disciplines that is specially bounded to the design process is manufacturing. Many times new products have been designed only to find out that the technology needed for its manufacturing was not readily available. 6.3.2. Design for manufacture and assembly

Hence, each component of the product must be designed not only to fulfill engineering requirements but also to be easily and cheaply manufactured. This emphasis is called design for manufacture, and it groups selection of materials, manufacturing methods, planning, assembly, testing and quality assurance. The design team must be capable of evaluating the impact that design changes have in manufacturing processes.

Kalpakjian & Schmidt (2001) define Concurrent Engineering as a systematic approach integrating the design and manufacture of products, with a view towards optimizing all elements involved in the life cycle of the product.

After the individual parts have been manufactured, they usually have to be assembled to make the final product. The importance of the assemblies cannot be understated, in many products assembly takes the largest time of the manufacturing process. Much can be done during the design phase to make the assembly as simple and fast as possible. Figure 6.12 shows some good and bad design practices regarding assemblies.

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c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

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6.3 Trends for the design process



Material extraction













































142

 

 

 





































































































































































Bad















































































































Manufacturing

Use

Recycle

Remanufacture

Reuse

Waste managment

Bad





Material Processing









































































Good













































































































































































































Bad

6.3 Trends for the design process

Good

Good

Figure 6.12: Design considerations for assembly. Figure 6.13: Stages of a product life cycle. After Otto & Wood (2001). Nowadays, computers are an integral part of the conceptual, refinement, evaluation and production phases of the design process either as engineering or management tools. The use of computers has greatly simplified the representation, study and construction of analytical models through Computer Aided Design (CAD), Computer Aided Engineering (CAE) and Computer Aided Manufacturing (CAM). 6.3.4. CAD, CAM, CAE and CIM

During the centuries the impact that humans have in the environment has grown steadily as both, populations and its needs, increase. In the last decades, the awareness about the consequences of extracting resources and dumping waste without control has modified the way engineers design.

6.3.3. Design for the environment

If populations is to keep enjoying the advantages of technological advances and higher standards of living for the centuries to come, products must have little or no impact in the environment. Design for environment (DFE) is a product design approach for reducing the impact of products on the environment. Most of the times, the impact of products into the environment is thought of in terms of their disposal. Nevertheless, products have an impact during all of its life cycle from the extraction of the materials it is made from up to their disposal (see figure 6.13).

These tools use computer software to assist in the creation and revision of engineering drawings and models (CAD), manufacturing (CAM), and analysis (CAE) of new products. The use of CAD/CAM/CAE tools avoids the need of making costly illustrations, models and prototypes, shortening the time needed to bring a new product from concept to production. Although these tools may be applied in different parts of the design process, they are better suited for certain parts of the process (see figure 6.14). Regarding Computer Integrated Manufacturing (CIM), Egan and Greene (1989) state that the appearance of CIM is based on the recognition that steps in the development of a manufactured product are interrelated and can be accomplished effectively and efficiently by using computers.

Products can have adverse impact on the environment during their manufacture through the use of polluting processes, the use of high amounts of raw materials, or the need of high quantities of energy. They can also have different levels of impact on their disposal due to large half-lives or the need of large amounts of energy for their destruction. As shown in figure 6.13 there are many opportunities for recycling, remanufacturing and reuse to reduce environmental impact. Unfortunately, products that are designed without this vision in mind are difficult to remanufacture, reuse or even recycle. Designers must use all their knowledge and creativity to create products that are environmentally friendly products throughout their manufacture, packaging, transportation, use and disposal.

CIM provides a mean to integrate all the steps in the manufacturing process taking into account processes, specifications, instructions and data that need to be controlled and organized.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

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6.3 Trends for the design process

6.4

Definition of product need; marketing information

Conceptual design and evaluation; feasibility study

Design analysis; codes/standards review; physical and analytical models

Prototype production; testing and evaluation

Computer Aided Design (CAD) Computer Aided Engineering (CAE)

Production drawings; instruction manuals

Material specification; process and equipment selection; safety review

Pilot production

Production

6.4 Failure Mode and Effect Analysis

Computer Aided Manufacturing (CAM) Computer Aided Process Planning (CAPP)

Computer Integrated Manufacturing (CIM)

Inspection and quality assurance

Packaging; marketing and sales literature

Failure Mode and Effect Analysis

The notion of a reliable product comes from two different parts. First, there is the minimization of performance variation across different environments and user conditions. Second, is the assurance that the product will work as intended, without falling short of a given set of customer expectations. The first part is achieved through customer quality. The second part is achieved through the more fundamental engineering quality. With the latter, it is ensured that the product has adequate strength, reliability and failure prevention. Traditionally, reliability has been achieved through extensive testing at the end of the design process. A better idea is to design from the early design stages incorporating the concepts of quality and reliability. Historically, engineers have not been very good at designing with reliability and quality. In most occasions, engineers use a safety factor as a way of making up for all the possible failure modes that were not considered in the design. As the engineer had less idea of what could go wrong with the product, the larger the safety factor that the engineer would use. Unfortunately, as stated in the Mechanical Engineering magazine: A large safety factor does not necessarily translate into a reliable product. Instead, it often leads to an overdesigned product with reliability problems. Failure Mode and Effect Analysis (FMEA) is an analytical methodology used as means for analyzing potential reliability problems early in the product design process, where it is easier and cheaper to take corrective actions. FMEA is used to identify potential failure modes, determine their effect on the use of the product, and identify counter-actions to correct them. FMEA focuses on the entire product and not just in the different components and interfaces, although failure modes may be related to specific components or interfaces. There are several types of FMEAs, each one with its own focus and objectives. Independently of the task at hand, FMEA should always be used whenever failures would mean potential harm or injury to the user. The types of FMEA are: 6.4.1. Types of FMEA

Product

Figure 6.14: The use of computer aided tools in the different steps of the design process (after Kalpakjian & Schmid, 2001). c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

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• System FMEA: focuses on global system functions c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

145

6.4 Failure Mode and Effect Analysis

6.4 Failure Mode and Effect Analysis

• Design FMEA: focuses on components and subsystems

• Capture engineering/organization knowledge

• Process FMEA: focuses on manufacturing and assembly processes

• Emphasizes problem prevention

• Service FMEA: focuses on service functions

• Documents risk and actions taken to reduce risk

• Software FMEA: focuses on software functions

• Provide focus for improved testing and development

According to the Society of Automotive Engineers (2002), FMEA supports the product development process in reducing the risk of failure by:

6.4.2. FMEA Usage

• aiding in the objective evaluation of design requirements and design alternatives • aiding in the initial design for manufacturing and assembly requirements • increasing the probability that potential failure modes and their effects on system operation have been considered in the design/development process

146

• Minimizes late changes and associated cost • Catalyst for teamwork and idea exchange between functions In order to effectively apply FMEA, the greatest challenge that the design team faces is to anticipate what might go wrong with a product. While anticipating every possible failure mode is almost always impossible, the development team should generate a detailed list of potential failures. Some questions that may help in this task are (Stamatis, 1995): 1. What does the product do and what are its intended uses? 2. How does the product perform its function?

• providing additional information to aid in the planning of through and efficient design improvements and development testing

3. What raw materials and components are used to build the product?

• providing an open issue format for recommending and tracking risk reducing action

4. How, and under what conditions does the product interface with other products?

• providing future references to aid in analyzing field concerns, evaluating design changes, and developing advanced designs

5. What by-products are created by the product or by the use of the product?

Properly used, FMEA provides the engineer with several benefits that include (Crow, 2002):

6. How is the product used, maintained, repaired, and disposed of at the end of its useful life? 7. What are the manufacturing steps in the production of the product?

• Improve product/process reliability and quality

8. What energy sources are involved and how?

• Increase customer satisfaction

9. Who will use or be in the vicinity of the product, and what are the capabilities and limitations of these individuals?

• Early identification and elimination of potential product/process failure modes • Prioritize product/process deficiencies c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

The above questions should be aimed to gather information in order to address six basic questions: c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

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6.4 Failure Mode and Effect Analysis

6.4 Failure Mode and Effect Analysis

148

1. What could fail or go wrong with each component of the product? 2. How or why can the part fail to meet its engineering specifications? 3. What circumstances could cause the failure? 4. To what extent might it fail? 5. What are the potential hazards produced by the failure? 6. What steps should be implemented to prevent the failure? The use of FMEA is straightforward consisting of a series of steps. Following the procedure suggested by Otto & Wood (2000), the 10 steps procedure is explained in what follows.

6.4.3. Step by step Design FMEA Analysis

Step 1: List each subassembly and component number, along with the basic functions or function chains of the component. The component numbers may be referenced from a product’s bill of materials. Likewise, the component functions should be consistent with the functional models and architecture developed for a product. Any functions listed for a component should concisely represent the design intent. Environmental and operational parameters, such as temperature, humidity, and pressure ranges, should be listed to clarify this intent. Step 2: Identify and list the potential failures for each product component. Simple prototype models and brainstorming techniques can aid in identifying potential failure modes. Likewise, sketches, storyboards, free-body diagrams, force-flow diagrams, and process-flow diagrams can help in understanding the physics of a failure mode. Tables 6.1 and 6.2 should be used to check for typical problems with components and product systems. For any listed failure mode, the idea is that the failure could occur, but not that will necessarily occur for the product under consideration. Step 3: List possible potential causes or mechanisms of the failure modes. Example causes include tolerance stack-up, assembly errors, poor maintenance, impact loading, overstressing, and so forth. These causes will provide insights into modeling of the failure mode. They will also indicate appropriate preventive measures that might be adopted.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

List of example failure modes Corrosion

Ingress

Delamination

Fracture

Vibrations

Erosion

Material Yield

Whirl

Thermal shock

Electrical short

Sagging

Thermal relaxation

Open Circuit

Cracking

Bonding failure

Buckling

Stall

Starved for lubrication

Resonance

Creep

Staining

Fatigue

Thermal expansion

Inefficient

Deflections or deformations Oxidation

Fretting

Seizure

UV deterioration

Thermal fatigue

Burning

Acoustic noise

Sticking

Misalignment

Scratching and hardness

Intermittent system operation

Stripping

Unstable

Egress

Wear

Loose fittings

Surge

Binding

Unbalanced

Overshooting

Enbrittlement

Ringing

Loosening

Loose

Scoring

Leaking

Radiation damage

Table 6.2: Abbreviated list of example failure modes. After Otto & Wood (2000).

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6.4 Failure Mode and Effect Analysis

Step 4: List the potential effects of the failure, including impact on the environment, property, or hazards to human users. Example effects include noise, poor appearance, flying debris, unpleasant odor, erratic operation and so forth. Step 5: Rate the likelihood of occurrence (O) of the failure. The ratings should be on a scale of 1-10 as given by:

1 2/3

No effect Low (relatively few failures)

4/5/6 Moderate (occasional failures) 7/8

High (repeated failures)

9/10

Very high (failure is almost inevitable)

Step 6: Estimate the potential severity (S) of the failure and its effect. Again, a 1-10 scale should be used. The following meanings are associated with this scale:

1

No effect

2

Very minor (only noticed by discriminating customer)

3

Minor (affects very little of the system; notice by average customer)

4/5/6 Moderate (most customers are annoyed) 7/8

High (causes a loss of a primary function; customers are dissatisfied)

9/10

Very high and hazardous (product becomes inoperative; customers are angered; the failure may result in unsafe operation and possible injury)

6.4 Failure Mode and Effect Analysis 1

Almost certain

2

High

3

Moderate

4/5/6 Moderate – most customers are annoyed 7/8

Low

9/10

Very remote to absolute uncertainty

Step 8: Calculate the Risk Priority Number (RPN). An RPN prioritizes the relative importance of each failure mode and effect on a scale of 1-1000. It can be calculated with the following relation: RPN = (S) × (O) × (D) A “1000” rating implies a certain failure that is hazardous and harmful and will occur, whereas a “1” rating is a failure that is highly unlikely and unimportant. Rating above “100” will occur, whereas ratings below “30” become reasonable for typical applications. It is important to notice that the RPN scale is nonlinear in risk. Step 9: Develop recommended actions for the failure modes, assign responsibilities to appropriate parties and team members, and set a schedule for implementing the actions. Corrective actions should be first developed for the highest ranked failure modes based on the RPN. Example actions include revised component or subassembly design, revised test plan or material specification, design of experiments and prototypes, etc. These actions should be specific. Step 10: Implement the corrective actions, update the S-O-D ratings, and recalculate the RPN for the updated design. The process and results of the FMEA should be documented, perhaps with the help of a template like the one shown in figure 6.15.

Step 7: List current or expected design controls/test for detecting (D) the failure before the product is released for production. A 1-10 scale is used to assess detection: c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

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151

6.4 Failure Mode and Effect Analysis

6.4 Failure Mode and Effect Analysis

152

D RPN O S

Improved situation

Applied steps O S

Current situation

Proposed test steps Failure Cause Failure Consequence

Failure Type

1. Cross, N. (1994) Engineering Design Methods, John Wiley & Sons. 2. Crow, K. (2002) Failure Modes and Effects Analysis (FMEA), DRM Associates, www.npd-solutions.com. 3. Cutherell, D. (1996) Product Architecture. Chap 16. in “The PDMA handbook of new product development”, edited by M. Rosenau, Jr. et al. New York: Wiley. 4. Kalpakjian, S. & Schmid, S. (2001) Manufacturing Engineering and Technology, fourth ed., Prentice-Hall. 5. Otto, K. & Wood, K. (2001) Product Design - Techniques in Reverse Engineering and New Product Development, Prentice-Hall. 6. Pahl, G. and Beitz W. (2001) Engineering Design - A systematic Approach. Second Ed. Springer. 7. Pugh, S. (1990) Total Design, Addison Wesley. 8. SAE (2002) Potential Failure Mode and Effects Analysis in Design (Design FMEA) and Potential Failure Mode and Effects Analysis in Manufacturing and Assembly Processes (Process FMEA) and Effects Analysis for Machinery (Machinery FMEA). SAE Standard J1739. 9. Stamatis, D. H. (1995) Failure Mode and Effect Analysis - FMEA from Theory to Execution. ASQ Quality Press. 10. Ullman, D. (2003) The Mechanical Design Process, Third Edition. McGrawHill. 11. Ulrich, K. (1995) “The role of product architecture in the manufacturing firm”. Research Policy, 24, 419-440. 12. Ulrich, K. & Eppinger, S. (2000) Product Design and Development. Irwin McGraw-Hill.

Failure Location

Name/Department/Supplier/Telephone

FAILURE MODE AND EFFECT ANALYSIS Design FMEA Process FMEA

D RPN

Suggested remedial measures

By (Name/Department/Telephone)

Component name

References

Figure 6.15: FMEA Template.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.

c Copyright 2004 Dr. Jos´ e Carlos Miranda. Todos los derechos reservados.