Housing Pattern By Rapidprtotyping

Modification and Development of “Housing Pattern” in Sand Casting with the aid of Rapid Prototyping Technology. Mangesh R. Dharme

D. B.Pawar

N. S. Pohokar

M.E. (CAD/CAM) Student Prof. Ram Meghe Institute of Technology & Research, Badnera, Amravati E-mail: [email protected]

M.E. (CAD/CAM) Student Prof. Ram Meghe Institute of Technology & Research, Badnera, Tooling Amravati E-mail: [email protected]

Lecturer In Mechanical Engineering Prof. Ram Meghe Institute of Technology& Research, Badnera, Amravati E-mail: [email protected]

Abstract (RT) have made it possible to reduce the casting tooling lead-time dramatically [8].

Rapid prototyping (RP) technology, involving automated fabrication of intricate shapes using a layer-by-layer principle, has matured over the last decade.

At least six different rapid prototyping techniques are commercially available each with unique capabilities these are Stereo lithography (SLA), Fused Deposition Modeling (FDM), Laminated Object Manufacturing (LOM), Selective Laser Sintering (SLS), Solid Ground Curing and Ink Jet Printing (IJP).

In this paper Housing (A cast iron, FG150) product is taken form M/S Jadhav Steel Alloys in Amravati. A CAD model of Housing Pattern is created and converted into stl file. Cost optimization by Build orientation of RP pattern on FDM has been conducted. A RP pattern is created and conventional sand casting is performed and cast dimension of both is compared there by proved the feasibility of R.P. pattern. This methodology has reduces the lead-time to a great extent. Thus rapid prototyping proved superior to traditional tool making in technical standpoint, especially where limited numbers are required.

The fused deposition modeling (FDM) is a rapid prototyping technology by which physical objects are created directly from a CAD model using layer by layer deposition of extruded materials. The technology offers the potential of producing parts accurately in a wide range of material safely and quickly.

The main input is a solid model of the part in a facetted format stored in a STL file, and the fabrication process is highly automated; no part-specific tooling is required. RP technology can produced physical parts from CAD model thus can be used to shorten “time to market”. This paper shows how the use of RP technology compresses the tooling development time for sand casting. It also describes the feasibility of RP in foundries.

1.1 FUSED DEPOSITION MODELING (FDM) Fused Deposition Modeling (FDM) was developed by Stratasys in Eden Prairie, Minnesota. In this process, a plastic or wax material is extruded through a nozzle that traces the parts cross sectional geometry layer by layer. The build material is usually supplied in filament form, but some setups utilize plastic pellets fed from a hopper instead. The nozzle contains resistive heaters that keep the plastic at a temperature just above its melting point so that it flows easily through the nozzle and forms the layer. The plastic hardens immediately after flowing from the nozzle and bonds to the layer below. Once a layer is built, the platform lowers, and the extrusion nozzle deposits another layer. The layer thickness and vertical dimensional accuracy is determined by the extruder die diameter, which ranges from 0.013 to 0.005 inches. In the X-Y plane, 0.001 inch resolution is achievable.

Keywords: -Rapid prototyping, Rapid Tooling, Fused Deposition Modeling, STL

1. INTRODUCTION Tooling development is an important activity bridging product design and manufacturing activities, and is often a bottleneck (in terms of geometry) in new product development. In metal casting sector, where long lead times (weeks to months) for producing the first article of approval are no longer acceptable. In metal casting process, the development of intermediate tooling (pattern and core boxes) accounts for more than 70% of lead time for the first article of approval and greatly influences the cost and dimensional quality of the final product. In the present manufacturing environment, it is vital for manufactures to bring their products to market as quickly as possible [6]. Rapid Prototyping (RP) and Rapid

This process is continued until the part is completed. Once complete, the part can be taken out and any support structures can be removed.

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1.4 RP IN SAND CASTING Pattern development is the main bottleneck (in terms of time and cost) for manufacturing intricate castings, especially for replacement purposes. The idea of using rapid prototyping (RP) in the sand casting for high or medium volumes initially seems unrealistic as materials costs and initial investment is high for the RP However, zero tool costs, reduced lead times and considerable gains in terms of freedom in product design and production schedules may significantly benefit RP manufacturing In metal casting process, the development of tooling (pattern and core- boxes) accounts for the first article of approval and greatly influences the cost and dimensional quality of the final product. Much of this time is spent in tool design and process planning. A combination of intelligent Computer-Aided Design, Rapid Prototyping promises to reduce the tooling lead-time by 50% or more. RP is increasingly being recognized as a significant technique in the battle to shorten the lead- time in sand casting. In the sand casting, patterns and cores can be produced for castings prototypes. The RP can be used as direct pattern (i.e. it is used to produce mould cavity directly). However RP pattern can be used as master pattern.

Fig. 1. Fused Deposition Modeling (FDM) s 1.2 FEATURES OF FDM: 1. FDM models are very strong and durable. 2. Models are stable and never warp/shrink. 3. Models can go through milling and boring operations. 4. Models can be sanded, painted and finished as required. 5. Large models can be built in multiple sections and joined with ease and accuracy.

2. RAPID PROTOTYPING PATTERN METHODOLOGY

6. Models are non-toxic and safe to handle.

CAD models were developed in solid modeling software for the parts. The relevant draft and shrinkage allowances were assigned to pattern solid models. The STL files were generated from these developed solid models. The generated STL files were transported to CATALYST, the pre-processing software in order to slice the objects to required thickness and determine the optimal build orientation. The output file generated by CATALYST was sent to FDM machine. The build orientation for each part geometry was carried out by changing its orientation 0 0 from 0º to 90 with the increment of 10 . Before building a part, it requires to specify the layer resolution, the part surface quality, the part interior style, and support style These build styles set parameters for all pre-processing operations: slice, support, and tool-path The output file generated by CATALYST provides necessary information and instructions to FDM machine to build the physical prototype.

7. Suitable for applications like, vacuum, sand and investment casting 8. Medical grade modeling material capable of being sterilized using gamma radiation. 9. High impact strength 10. Resistance to high temperature 11. Chemical resistance properties 1.3. NEED FOR RP TECHNOLOGY The product manufacturing industries are facing two important challenging tasks, substantial reduction of product development time and improvement on flexibility for manufacturing small batch size products. CAD/CAM has significantly improved the traditional production design and manufacturing. However, there are a number of obstacles in true integration of CAD with CAM for rapid development of new products. Despite the substantial research in CAD/CAM technology, the gap between CAD and CAM has been identified in aspects: (1) Rapid creation of 3-D models and prototypes and (2) Cost-effective production of patterns and moulds with complex surfaces. To substantially shorten the time for developing patterns, moulds, and prototypes, RP is an ideal method for complex patterns making and component prototyping. RP has been proved as better alternative for pre-manufacturing research in engineering field [7].

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2.1 2D DRAWING OF HOUSING PATTERN

2.2 3D- CAD MODELS OF HOUSING

Housing pattern (A cast iron, FG150) product is taken form M/S Jadhav Steel Alloys in Amravati as shown in Fig.2. and Fig.3. Shows the wooden pattern presently use for casting.

By using Auto CAD and Pro- E a solid model of Housing and Housing Pattern is created.

Fig. 4. 3D MODEL OF HOUSING

Fig 2D Drawing of Housing Pattern Fig. 2. 2D Drawing of Housing Pattern

Fig.5. 3D Cad Model of Wooden Housing Pattern (Pattern no 1) Fig. 3. (a) -Wooden Patterns of Housing

(Pattern no 2) Fig. 3. (b) -Wooden Patterns of Housing

(Pattern no 1) Fig. 6. (a) 3D Model of Housing Pattern

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(Pattern no 2) Fig. 6. (b) 3D Model of Housing Pattern

(Pattern no 2) Fig. 7. (b) STL File of Housing Pattern

2.3 CONVERTING STL FILE FROM CAD FILES

2.4 SLICING THE STL FILE

Most of the current CAD software can directly output an STL file from a CAD model, but the actual command may change depending on various versions The following example are the methods used for generating an STL file from CAD files.

The generation of a series of closely spaced 2D crosssections of a 3D object is known as slicing. Generally, the user can specify the Z-thickness of the slice. Typical thickness is .0006 in. This is always an approximate process. The main error associated with this is the staircase error because the surface finish in the Zdirection will not be good. After the STL part is properly oriented and positioned, the user then slices the part into layers After the part is sliced, it automatically generates the support structure, as most RP software does. For the first orientation, five layers of support material were generated under the base. Five layers is the machine default in order to allow the part not only to hold tight to the plastic sheet in the FDM machine, but also to allow the part to be easily separated from the plastic sheet after the build is complete.

Making STL files from Pro-Engineer 1. Click on file, save copy 2. Select the file type STL 3. In the Export STL dialog box, set Format to Binary files are about 1 ⁄ 5 the size of ASCII files 4. Set the Chord Height to 0.001 in. The field will be replaced by a minimum Acceptable value for the geometry of the model. 5. Set Angle Control to 0.5 6. Name the file and click the OK button ProEngineer will save your STL file, and display your triangles on the screen as shown in fig below.

The STL file is open in “Catalyst” preprocessing software. The STL file is then preprocessed in the “catalyst” showing the model is break up into slices and shows the support material and structure in blue color and red color.

(Pattern no 1) Fig. 7. (a) STL File of Housing Pattern

Fig. 8. Model and support building for part oriented at 90º about x-axis

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After the orientation and the support decision have been made, the user then determines the tool path that the machine will use to build each layer The tool path allows a great variety of options to the user depending on finished part strength, build time, or weight and surface finish One of the biggest variables is the orientation of the tool path. The software allows the user to set the orientation in each layer. For a more isotropic part, it automatically sets the layers to a ±45º orientation with the exterior boundary curve. It also has the capability to generate a ‘‘hollow’’ part by creating a tool path with larger air gaps in the middle that forms a mesh-like interior. This sparse fill, as it is called, dramatically decreases material used, which in turn increases the build speed of the part.

Both pattern no 1 and pattern no 2 are identical but the only difference between pattern no 2 with pattern no1 is a square slot in the later therefore by using rapid prototyping machine pattern no2 is produce. After creating pattern no2 if we fill up square cavity of that with wax or any other material we can use it like a pattern no 1 and there is no need to produce pattern no 1 Hence we can save the cost of pattern no 1.

Fig. 11. Rapid Prototyping part square cavity fills up with the wax

Fig. 9. This ‘‘sparse fill’’ generates a hollow part that is created with tool paths with larger air gaps in the middle that forms a mesh-like interior.

3. DETERMINATION OF COST In order to determine the total cost, the influencing parameters like model material, support material, base plate, annual maintenance contract, electricity, battery depreciation and machine depreciation, etc. was considered. The material cost was computed based on volume of material used and the unit price of material. The FDM process employs external support structure to the part being built. In this process, the consumed material has two parts: the amount of material to build the part, called as model material and the amount of material used to build the support, called as support material. Model material cost (Cmm) and support material cost (Csm) were considered equal while computing the total cost (Ctc). The costs associated with the other dominant parameters include, base plate cost (Cbp), electricity cost (Cel), battery depreciation cost (Cbd), machine depreciation cost (Cmd) and the annual maintenance cost (cam). From these cost components, Equation (1) was derived to compute the total costs.

2.5 BUILDING AN RP PART Once the STL file is sliced and transferred into an RP machine, the build process is fully automated Fig.10. Shows a part built in FDM Maxum.

Ctc = Cmm + Csm + Cbp + Cel + Cbd + Cmd + Cam-( 1) The part post processing cost was not considered while computing the total cost. Fig. 10. Rapid Prototyping part

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Following cost elements have been considered for cost estimation of RP pattern. 1

Model Material Cost:(Cmm)

Rs.13.95/cm3

2

Support Material cost: (Csm)

Rs. 267.5/ plate

3

Base Plate cost: (Cbp)

Rs. 267.5/ plate

4

Electricity Cost: (Cel)

Rs. 0.12/min

5

Battery Depreciation cost:(Cbd)

Rs.0.01826/min

6

Machine depreciation: (Cmd)

Rs.0.0684/min

7

Annual Maintenance cost: (Cam)

Rs. 0.9132/min

Contract

Fig. 12. Conventional Sand Casting

The Housing Pattern shown in above figure is processed in preprocessing software (CATALYST software). The following were the requirements for the RP pattern. Model material:

152.75 cm3

Support material:

17.57 cm3.

Estimated build time:

468 min.

Chargeable base plate area:

64 in²

By considering above cost elements the calculated cost of RP pattern is Rs. 4000. The cost for RP pattern is compared with the wooden pattern and metal pattern.

4. CONVENTIONAL SAND CASTING PROCESS: Ground molding is selected for making Housing casting. Sand casting, the most widely used casting process, utilizes expendable sand molds to form complex metal parts that can be made of nearly any alloy. Because the sand mold must be destroyed in order to remove the part, called the casting, sand casting typically has a low production rate. The sand casting process involves the use of a furnace, metal, pattern, and sand mold. The metal is melted in the furnace and then ladled and poured into the cavity of the sand mold, which is formed by the pattern. The sand mold separates along a parting line and the solidified casting can be removed. The process are described in greater detail in the following fig. 12.

Fig. 13. RP Pattern Casting

Fig. 14. Wooden Pattern Casting

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5. COMPARISON OF RP AND WOODEN PATTERN CASTING Housing Casting from RP and Wooden pattern is obtained as shown in Fig.13 & Fig.14. The dimensional comparison of some key dimension is shown in tables below, S. No

Actual Dimension on drawing (mm)

Dimen sion for cad model (mm)

Dimensio n on RP pattern (mm)

Dimensio n on Wooden Pattern (mm)

Difference in RP and Wooden Pattern (mm)

1

Ø74+2/-0

Ø 76

Ø 76

Ø 75.7

0.3

2

+1/-1

Ø 63

Ø 62.9

Ø 62.5

0.4

Ø 114

Ø 114

Ø 114.2

0.2

64.5

64.4

64.5

0.1

100.5

100.5

100.3

0.2

Ø 62

3

Ø 114

+0/-2

64+0.5/-1

4 5

100

+0.5/-0.5

Fig. 16. Difference in RP and Wooden Pattern Casting Dimension The dimension difference of both the Pattern and cast are acceptable and hence prove the use of RP generated model (ABS material) is suitable for tooling (pattern).

Table. I. Difference in RP and Wooden Pattern

5.1 COST & LEAD TIME OF PATTERN: Cost & Lead Time of Pattern & Core Box for the RP Pattern and Wooden Pattern is shown in Table III

Actual Dimension on Drawing (mm)

Dimensi on on RP pattern casting (mm)

Dimension on wooden pattern casting (mm)

Difference in RP and wooden pattern casting (mm)

1

Ø74+2/-0

Ø75.1

Ø75.4

0.3

2

Ø 62

+1/-1

Ø62.5

Ø62.3

0.2

3

Ø 114+0/-2

Ø113.3

Ø113.1

0.2

4

64+0.5/-1

63.9

63.5

0.4

100.2

100.4

0.2

5

100

+0.5/-0.5

Wooden pattern

RP pattern

Lead time (In Hrs)

240

10 Hrs

Min. Cost (In Rs.)

1200

4000

Table III: Comparison of Cost and lead-time of RP and Wooden Housing pattern

Fig. 15. Difference in RP and Wooden Pattern Dimension S.No

Characteristics

Table. II. Difference in RP and Wooden Pattern Casting Dimension

Fig. 17. Lead Time Required to Fabricate the Housing Pattern

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prototyping and lead-time as well as provides the solution for the medium scale production. This technique reduces the tooling cost and labor cost. The RP job once fired do not need any attention and any alteration needed in the job can be easily done with less labor. Closer tolerances can be maintained between the mating parts as well as the dimensional accuracy of RP is better than the traditional process. If the more number of similar jobs are made on RP are all alike & dimensionally accurate.

7. REFERENCES [1] Kenneth G. Cooper, “Rapid Prototyping Technology Selection and Application”, Marcel Dekker. Inc. New York, First Edition, pp 1-2

Fig. 18. Costs Incurred to Fabricate Housing Patterns

[2] Frank W. Liou, “Rapid Prototyping and Engineering Applications, A toolbox for prototype development”, CRC Press, New York, pp 215-297

As shown in above Fig the cost of RP pattern is very high as compared to wooden pattern but RP Patterns are dimensionally correct as they are produced from RP machine, which is automated process. With these patterns, the closed tolerances can be maintained with a good quality of Mould. Casting from such patterns requires lesser Machining actives and time as well. Therefore the cost and time require for post processing of RP casting is low as compared to wooden casting and hence it is beneficial to use RP pattern as compared to wooden pattern.

[3] Ian Gibson, “ Advanced Manufacturing Technology for Medical applications, Reverse Engineering, Software Conversion and Rapid Prototyping” John Wiley & Sons Ltd, west Sussex, England pp 1-14 [4] Rao P.N., “CAD/CAM, - Principles and Applications” TATA McGraw Hills, New Delhi, First Edition, pp 104 [5] Walker J. M., “Handbook of Manufacturing Engineering”, Dekker Publication USA Second Edition, pp-437

6. CONCLUSIONS

[6] Pal D.K, Ravi B, Bhargava LS, (2002), “E-manufacturing one-off intricate castings using RP technology”, Int. Conf. On e-manufacturing, Bhopal, pp259-263

New technologies not only improve and replace conventional methods but also offer the chance for new types of products and developing procedures and in this process it needs the knowledge on the potentials of these evolving in many fields of applications such as Engineering product development, Medical and surgical applications, Art models etc.

[7] Chakradeo A., Kulkarni M.A., (2002), “Rapid prototyping – A tool for pre-surgical planning”, Int. Conf. On emanufacturing, Bhopal, pp. 271-272.

RP systems offer the opportunities to make products faster and usually at lower costs than using conventional methods. Since RP can substantially reduce the product development cycle time, it can be used to develop the accurate models directly from designs generated from computers. The bottlenecking in pattern development by conventional methods can be overcome by using the RP technology. To stay ahead in competition, the updated technology demands development of fast and accurate castings of high standards from foundries. The sand cast components manufactured using RP patterns shown better results for dimensions and surface finish as compared to the conventional method.

[8]. Sayed H Masood, “Intelligent Rapid Prototyping with Fused Deposition Modeling”, Rapid Prototyping Journal, Vol. -2, No. 1. 1996, Pp 23-24. [9] Choi S.H., Chan A.M.M., (2004), “A virtual prototyping system for rapid product development”, Computer Aided Design, Vol. 36, pp. 401-412. [10] Horvath I., Yang D.Y., (2002), “Rapid technologies: solutions for today and tomorrow”, Computer Aided Design, Vol. 34, pp. 679-682.

The present work describes the process of sand casting using Rapid Prototyping. Rapid Prototyping reduces cost of

[11] Kochan A., (1997), “Rapid prototyping trends”, RP Journal, Vol.3 No.4, pp.150-152.

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