Rapid Pro To Typing

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Stereolithography

INTRODUCTION Introduction new products at ever increasing rates is crucial for remaining successful life in a competitive global economy decreasing Product development cycle times & increasing product complexity require new ways to realize innovating ideas. In response to these challenges, industry & academia have invented a spectrum of technologies that help to development new products & to broaden the number of product alternatives. Rapid prototyping is one of the techniques. The term rapid prototyping refers to class of technologies that can automatically construct physical models from computer aided design (CAD) data. These “three dimensional printers” allow designers to quickly create tangible prototypes of their designs, rather than just two-dimensional pictures. Such models have numerous uses. They make excellent visual aids for commenting ideas with coworkers or customers. In addition prototypes can be used for design testing for example an aerospace engineer might mount a modal air foil in a wind tunnel to measure lift & drag forces designers have always utilized prototypes, of rapid prototyping technique allows them to be made faster & less expensively.

REPID PROTOTYPING TECHNIQUES Rapid prototyping techniques is the name given to the class of manufacturing processes that allow objects to be constructed by building up a structure from individual layers. The layered construction method allows complex structure to be built that would be prohibitive or impractical using more traditional methods, and in a fraction of time. At present time, there many different processes that fall under this umbrella term, using a variety of materials and methods. What they have in common is that they may each be given as input a three dimensional model (described by a computer file), along with a set of perimeters particular to the process. The computer model is automatically sliced into layers by calculating its intersection with a set of parallel planes, spaced according to the resolution of the process. Each of the processes then constructs the object by building up reproductions of these layers in physical material. Most commercially available rapid prototyping machines use one of the six techniques. • Laminated Objected Manufacturing. • Fused Deposition Modeling • Sterolithography • Solid Ground Curing. • Selective Laser Sintering • Three Dimensional Printing Rapid prototyping is widely used in automotive aerospace, medical and consumer products. Although the possible applications are virtually limitless, nearly all full into one of the following categories. Prototyping, rapid tooling or rapid manufacturing. STEREOLITHOGRAPHY Stereolithoraphy is one of the several available methods of predicting rapid prototype models. The process allows complex shapes to be reproduction in polymer resin, going from computer data to finished product within a period of 24 hours. Rapid prototyping techniques are increasingly being used by industry to produce models in a fraction of time required for more conventional mfg. Methods. Stereolithogphy is widely used through all manufacturing industries to accelerate the design product development process by addressing three application areas: models patterns and masters. The main component of a Stereo lithography system a vat containing liquid photopolymer, galvanometer controlled mirrors, directing a UV laser onto the surface of

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Stereolithography liquid and just below the surface, vertical elevator tray. The Stereo lithography process is basically comprised of 4 major steps. I) CAD Process I) Part Preparation II) Setup and Build. III) Post Processing. 1. CAD Process The CAD process involves the utilization of a CAD system to structure object/ part date for use on the Stereolithography apparatus (SLA). The process being with a design created on a solid modeling CAD system. Pro/Engineer and Auto CAD 13 with 3D modeling extension are 2 examples available 3D modeling software packages. 2. Part Preparation This process is performed utilizing the SLA manufactures proprietary software. Typically, 3 part orientation tasks are performed. These include : placing the parts in positive space, orienting the parts in such a way as to minimize support structure and positioning the parts to optimize the total number of parts to be made during the build process. At this stage of the part preparation process, if required, the parts can easily be scaled up or down in size. One orientated, the parts are then supported. Support structure is required to hold a part in place on the elevator tray and support any overhanging surfaces that are greater then 1/8” at any angle less than fifty degree from horizontal. Support structures are basically thin vertical webs. These parameters which are defined on a spread sheet include part build layer thickness (0.006 in), resin shrinkage compensation for increased part dimensional accuracy, resin specific parameters, setting time between layers and wiper arm start point and sweep pattern. 3. Setup & build The third step of the Stereolithography process involves the initialization & setup to build parts on the SLA. Prior to initializing the build process, the laser is warmed up for 15 min. The time required allows the laser to stabilize and reaches maximum output capacity. During the warm up period three tasks are performed: transfer of slices and operational data files from slice workstation to SLA control computer, lowering of platform into vat and resin level adjustment. The process of SLA software is now activated by the operator, which begins building the part by moving a focused laser beam across the surface of the vat of resin. The laser draws the first support cross-section, which adheres to the platform. Typically .3 inches of base support structure of built up before initiating the part build itself & whatever additional support are needed for over hanging surfaces. 4. Post processing The final step post processing involves cleaning UV curing & final finishing of the part. First, the part is raised out of the vat & as much liquid resin as possible is allowed to drain off the part. The part & the platform are then removed from the process chamber & the remaining excess liquid resin is removed by rinsing in a solvent with the aid of an ultrasonic cleaner. The part is then removed from the platform & support structure is removed from the part. Ultraviolet light to solidify any remaining trapped liquid & increase strength of part. Post curing is required, since a part is only about to go percent cured by SLA’S ultraviolet laser when it is built. The final cured part can be finished in a number of ways. Finishing techniques such as sanding, sand blasting, painting, polished can be applied. The steriolithoraphy lab is equipped with majority of items required for finishing which include a sand blaster.

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Stereolithography BENEFITS OF STEREOLITHOGRAPHY Wherever there is a product to be designed, manufactured & sold, there is an application for Stereolithogrphy. Almost every type of product design, from jet engines to perfume bottles, requires a prototype or mode. Stereolithography provides a fast efficient solution. Even collages & universities are finding Stereolithography of great benefit in teaching & research programs. The early exchange of ideas among those work concurrently to create & market innovative products is a key to success in today’s global marketplace. Sterolithography is an enabling technology to concurrent engineering that allows products design, engineering, R & D, manufacturing, marketing purchasing operations and corporate management to work as a more cohesive team to achieve batter design, efficiency, productivity, & quality. And these benefits are just the beginning speed & cost savings can be considerable when Sterelithography is compared to traditional prototyping process. Because concept models can be produced within hours, more design iteration can occur without impacting time to market. Design problems can be solved before production, avoiding costly redesign & retooling. And by eliminating costly manual procedures & programming of machine tools, the development cycle is shortened. As a result, product quality assurance levels rise significantly providing further competitive advantage in reducing warranty cost. LIMITATIONS OF STEREOLITHOGRAPHY The resins used in stereolithography are not capable of bearing the types of loads endured the production parts, so structural testing is generally not possible. APPLICATIONS OF STEREOLITHOGRAPHY Design Review Rapid prototypes allow users to quickly evaluate a design for potential problems. Simple errors which can be hard to pick up in a standard two dimensional CAD drawing are obvious once the designer can hold a real part or tool in his hand. Design Verification Users can actually put actual size prototypes in to the parts intended spot to test for accurate fit. Previously expensive molds had to be tooled before a prototype could be tested within a structure. If the prototype did not fit, because of an error in the geometry of the part, the tools have would have to be changed. Patterns For Moldes Stereolithography is not just for making prototypes. Many companies are now using Stereolithoraphy to make injection molds for their plastic & rubber parts. Stereolithography molds can be cast in hours pr days rather than weeks, and they cost a fraction of the price of standard mold. Presentations Companies can now do marketing presentations with real three-dimensional models. Customers benefit by seeing and touching model of the part or tool they went to purchase, rather than an abstract 2 dimensional wire drawing or diagram. Short Run Production Small volume products which previously would not be considered by manufactures due to tooling cost, can now be produced and shipped in days. This allows manufactures more flexibility to meet special customer requirements.

CASE STUDY: APS IS COMPANY (U.S.A.)

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Stereolithography APS IS a company which produces stereolithography parts by consulting with customer. It offers a state of art technology in stereolithography. APS had delivered prototype parts in less than 24 hours.

Situation: Marketing U.S.A. specializes in helping individuals and companies develop and bring new product to market. On May 19, 1998, the Sheboygan, Wisconsin based company decided to manufacture and market product idea it had patented, the Deco-hanger. This special tool consists of special plastic chips and an extendable pole with a special end cap. The Deco-hanger is designed to conveniently hang holiday light strings or garlands on gutters. to make in market in time for the Christmas in 1998 season , the company needed a finished product prototype on May, 30.

Assignment: APS was asked to use 2D drawing made by Sheboygan into a product prototype in time for May, 30.Producing plastic chip hangers required working with several materials to find one with right elasticity and colour qualities. APS worked with three plastics before finding the materials with right qualities.APS used software to create SL mould based on 3D CAD models to produce pole end with special knobs for hanging and removing clips. A SL prototype and the pole end cap were later used to cast a mould in high temperature composite material. by using stereolithography technique, APS produced the final product prototype in time to allow Marketing U.S.A. to show it at the May, 30 trade just 9 working days after starting the project. RAPID PROTOTYPING IN INDIA With its strong engineering base, liberalized economy and rising consumerism, India is expected to rapidly increase its industrial output in terms of both engineering and consumer products for domestic as well as export market. However, a majority of the products are direct descendents of similar products elsewhere, product innovation at a grassroots level is yet to take off in a major way. Moreover, the appreciation of time as a competitive factor is only just beginning to emerge. Even if the prototypes are manufactured in a day instead of several weeks, other bureaucratic hurdles delaying the project would negate the competitive advantage of rapid prototyping. It therefore appears that in short term, the cost of rapid prototypes would have to be comparable to those producted by conventional routes. Thus of rapid prototyping technology would find the greatest use in fabricating small and highly intricate components. The major and immediate attraction of rapid prototyping would be in producing the patterns, moulds and dies for metal casting, plstic injection molding and sheet metal forming industries.

CASE STUDY: In 1998 at beech candy hospital (Mumbai) A thirty five year old person was having tumor in brain. Doctor removed out X-ray film but he could not get the idea about carrying surgery. He called mechanical engineer who was knowing of rapid prototyping technique. Doctor asked that person to prepare prototypes of brain with tumor. That person did so and he placed 2 prototypes in front of doctors .By comparing the prototypes, doctor could get the idea & surgery was carried out successfully.

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Stereolithography CONCLUSION: Rapid prototyping is an enabling technology for concurrent engineering. Its goal is to reduce product development and manufacturing costs and lead times, thereby increasing competitiveness. Impressive steps towards the goal have been made. However, the field of of rapid prototyping technique is still new, with much efforts to be expended on improving the speed accuracy, and reliability of of rapid prototyping technique systems and widen the range of material for prototype construction. Another area of improvement will be costing, as most of rapid prototyping systems are currently expensive to be affordable by any but the large firms. Although of rapid prototyping technology will continue to be available to all companies via bureaux, which often in partnership with traditional model markers can provide a comprehensive service from design through to short run production, the future is likely to see more user-owned of rapid prototyping technique machines as their costs are reduced. There will also be two different types of of rapid prototyping technique systems for two distinct markets the design office “3D-Plotter” for rapidly generating parts for design verification and workshop/ model making shop machine for producing accurate functional parts.

BIBLIOGRAPHY TEXTBOOKS: Rapid Prototyping and tooling By, K.P.Karunakaran and V.P.Bapat RP cell, IDC, IIT Bombay. Manufacturing Engineering & Technology By Kalpakjian , Addision-wesley Publication 3rd Edition A Comparison of Rapid Prototyping Technologies By D.T.Pharm, R.S.gault International Journal of Machine tools & Manufacture “Saving Time, Money & Resources” Agricultural Engineering Page no.11-15 Nov 1991 “Computer Aided Journal” Nov.1996, March 1998..Penton Publication.

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