Conference Paper

Experimental corroboration of investment casting using Fused Deposition Modeling process of Rapidprototyping Dr. A. M. Kuthe1; K. M. Ashtankar2; D. S. Ingole3 • • •

1

Visvesvaraya National Institute of Technology, Nagpur and corresponding author. Visvesvaraya National Institute of Technology, Nagpur. 3 Sree Ram Meghe College of Engineering, Badnera, Amravati, Maharashtra. 2

Introduction The techniques based on layer-by-layer manufacturing i.e., rapid Prototyping are extending their fields of application, from the building of aesthetic and functional prototypes to the production of tools and moulds. In particular, additive construction applied to the production of dies and electrodes, directly from digital data, is defined as rapid tooling (RT). Patterns, cores and cavities for metal castings can be obtained through rapid casting (RC) techniques (Bernard et al., 2003; Rooks, 2002; Song et al., 2001). In both cases, since the tooling phase is highly time consuming, great competitive advantages can be achieved by means of rapid prototyping to solutions ensuring a short time-to-market scenario. Moreover, RT and RC processes allow the simultaneous development and validation of the product and of the manufacturing process. The relevance of RC techniques consists, above all, in a short time for parts availability. Traditionally, in order to produce cast prototypes a model and eventual cores have to be created, involving time and costs that hardly match the rules of the competitive market (figure 1). For this reason, functional tests are typically performed on prototypes obtained by metal cutting (Rooks, 2002), which are not effective in outlining issues related to the manufacturing process. The initial cost increase can be repaid through a reduction of costs and time for the following phases of development, engineering and production (figure 2.), as well as trough non-monetary advantages (Bernard et al., 2003). In particular, for relatively small and complex parts, the benefits of additive manufacturing can be significant, (Bak, 2003; Wang et al., 1999; Ramos et al., 2003). In this field, innovative solutions are now available based on 3D printing process, which can extend RC possibilities to the lower costs with respect to previous technologies such as selective laser sintering of sand (Gatto and Iuliano, 2001). One such technological solution consists in investment casting with the help of ABS-plastic patterns produced on Fused Deposition Modelling technique of Rapid Prototyping.

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A key issue regarding the investment casting process is the production of the dies which is uneconomical and time

Figure 1. traditional method of investment casting

consuming. Rapid prototyping techniques can meet this requirement, producing

single/few parts in short times and without tooling costs. The geometrical complexity are also achievable with layer manufacturing, suitable also for undercuts and hollow parts. Many solutions have been proposed, based on different technologies and materials. The present research regards ABS (Acrylonitrile

Figure 2. Rapid casting (RC) method

butadiene styrene) patterns obtained by Fused Deposition Modelling process on which, as in the conventional process, the ceramic

block can be built and then evacuated to obtain the cavity for pouring metal. Experimental studies regarding this solution are lacking in literature, in particular the technological feasibility in the case of burning of the ABS-part needs to be assessed and the process parameters needs to be optimized. Experimental plan The research regarded the experimental investigation on the use of ABS plastic as an ‘invest’ in the block-type investment casting process. The mould material is the Zirconium sand ‘Biosol’ ceramic slurry manufactured by a German Company and is widely used for making dental implants. The plan is to conduct the experimentation with following objectives: •

To verify the ABS-plastic material as a invest for investment casting process. 2|Page

•

verifying the feasibility of the investment casting process with FDM make patterns in the case of block moulding.

•

evaluating eventual critical parameters in the investment casting process.

•

Predicting the required parameters like temperature, time, and wall thickness for getting the cavity inside the mould.

For the described purposes, an ABS-plastic cylinder made in spars was chosen as a specimen. The experimental procedure started with the CAD modelling of the specimen (Figure 3), having 4 cm diameter and 2 cm length making total volume of 25.12 cc. In the subsequent stages, the length of the specimen has been increased by 1cm respectively.

First of all the ABS-plastic as an investment casting checked out with

feasibility of

Figure 1. the specimen cylinders

invest in the process is the help of a

small experiment. A small ABS-plastic part (figure 4) is kept in the muffle furnace for10 minutes by varying the temperature by 50 0C in stages. The different states of the ABS-plastic

Figure 3. Specimen used for the experimentation

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is shown in figure 5 and 6 respectively. The observation is recorded as shown in the observation table 1.

The volume of the mould material was also varied depending on the volume of the ABS part and keeping wall thickness constant. The gating and feeder

Figure 4. ABSplastic at the begining

Figure 5. ABSplastic at 100 oC

Figure 6. ABSplastic at 500 0C

system of wax are attached to the specimen as shown in figure 7. The mould block then allowed to become solid by currying it for 12 hours(figure8). Then it was kept in muffle furnace to evaporate the ABS plastic and to get the cavity inside it (figure 9). Then the mould was broken down after every stage to see whether the cavity is ready for pouring or not (figure 10). The time and temperature for complete evaporation of the part is observed as shown in the observation table 2.

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Figure 7. the block after backing in the furnace.

Figure 8. breaking of the block

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Table 1. effect of temperature on ABSplastic

Measuremants and results To study the effect of temperature on ABS-plastic a small piece of it is kept in the muffle furnace for various temperatures and the effect thereof is noted as shown in table 1 below. To study the effect of various parameters like temperature, time, volume of ABS-plastic and that of mould material (i.e., Zirconium sand), one parameter is varied at a time keeping other parameters constant as shown in table 2 and the results are noted along with the remarks.

Figure 9. specimen ready for the making of mould

Figure 10. the block ready for baking in the muffle furnace

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0

Temperature in C Table 2. effect of various parameters like volume of ABS-plastic, Material temperature, time, shell thickness on ABS-pattern inside the block 100 200 250 300 350 400 450 500

ABS-

Liquid form

plastic

Sr. No.

Volum e of ABSplastic

Varorization starts

Time

Vaporization continues

Temp.

-do-

-do-

Volume Shell of mould thickmaterial ness

( min.)

(0 C)

(cc)

(cm)

-do-

-do-

Evaporates completely

Result

Remark

(cc) 1.

25.12

15

500

282.60

1.0

Half burn

Block cracked

2.

25.12

15

500

282.60

1.2

Half burn

Block cracked

3.

25.12

15

500

282.60

1.4

Half burn

Block cracked

4.

25.12

15

500

282.60

1.6

Half burn

Block intact

5.

25.12

15

500

282.60

1.5

Half burn

Block intact

6.

25.12

20

520

282.60

1.5

Half burn

Block intact 7|Page

7.

25.12

25

520

282.60

1.5

Half burn

Bloke intack & Residue remaining

8.

25.12

30

520

282.60

1.5

90% burn

Bloke intack & Residue remaining

9.

25.12

35

520

282.60

1.5

90% burn

Bloke intack & Residue remaining

10.

25.12

40

520

282.60

1.5

Complete burn

Bloke intact & few resesidue

11.

25.12

40

520

282.60

1.5

Complete burn

Same as above

12.

37.68

40

520

308.51

1.5

Complete burn

Same as above

13.

50.24

40

520

331.41

1.5

Complete burn

Same as above

14.

62.85

40

520

354.12

1.5

Complete burn

Same as above

15.

75.42

40

520

372.65

1.5

Complete burn

Same as above

16.

88

40

520

392.42

1.5

Complete burn

Same as above

17.

100.57

40

520

412.52

1.5

Complete burn

Same as above

18.

113.14

40

520

434.96

1.5

Complete burn

Same as above

19.

125.71

40

520

470.85

1.5

Complete burn

Same as above

Conclusion The feasibility of investment casting starting from FDM manufactured ABS-plastic patterns was proven in the case of wall thickness of 1.5 cm and above, excluding problems of very small residues after the pattern burning out. This solution does not imply any limitation in the alloy to be cast. The technique provided satisfactory results for block moulding. With respect 8|Page

to traditional investment casting process, this technique ensures a much lesser time to get the product and higher geometrical freedom especially the natural shapes and higher order surfaces. The process limits can be identified in the surface finish of castings, which will be the objective of future developments of the research. Also the same experimentation can be carried out for the ‘shell moulding’ type of investment casting to prove its usefulness in that type of investment casting. A quantitative application of such tools would require the collection of comprehensive data about the innovative mould materials. Various other low cost mould materials like Portland cement, white putty and plaster of paris (POP) can also be tried to reduce the cost. Similar type of an experiment is carried out and it is found out that the Portland cement and white putty are good mould materials except the fact that Portland cement has poor Collapsibility. As a conclusion, the proposed solution of ABS-plastic as an invest in block type investment casting process is proved to be effective for the production of cast technological prototypes, in very short times, avoiding any tooling. Based on the results of this initial study, an interesting development of the research could be the assessment of the technique for other investment casting processes and parts produced with the other materials, aiming at the construction of a database for the accuracy and feasibility of this solutions. References •

Ingole D. S., Kuthe A. M. (2009), “Rapid prototyping- a technology transfer approach for development of rapid tooling”, Rapid Prototyping Journal, Vol.15 No. 4, pp.280290.

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Ingole D. S., Kuthe A. M. (2008), “Coding System for rapid prototyping industry”, Rapid Prototyping Journal, Vol.14 No. 4, pp.221-233.

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Elena Bassoli, Andrea Garro, Luca Iuliano, “3D printing technique applied to rapid casting”, Rapid Prototyping Journal, Vol. 13, No. 3, pp. 148-155.

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Bak, D. (2003), “Rapid prototyping or rapid production? 3D printing processes move industry towards the latter”, Rapid Prototyping Journal, Vol. 23 No. 4, pp. 340-5.

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Bernard, A., Delplace, J.C., Perry, N. and Gabriel, S. (2003), “Integration of CAD and rapid manufacturing for sand casting optimisation”, Rapid Prototyping Journal, Vol. 9 No. 5, pp. 327-33.

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Gatto, A. and Iuliano, L. (2001), “Effect of the post curing process parameters choice on part produced by direct croning process”, in Lonardo, P.M. (Ed.), Proceedings of PRIME 2001 – 1st International Seminar on Progress in Innovative Manufacturing Engineering, Sestri Levante (Genoa).

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•

Ippolito, R., Iuliano, L. and Gatto, A. (1995), “Benchmarking of rapid prototyping techniques in terms of dimensional accuracy and surface finish”, Annals of the CIRP, STC E, Vol. 44 No. 1, pp. 157-60.

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Ramos, A.M., Relvas, C. and Simo˜ es, J.A. (2003), “Vacuum casting with room temperature vulcanising rubber and aluminium moulds for rapid manufacturing of quality parts: a comparative study”, Rapid Prototyping Journal, Vol. 9 No. 2, pp. 1115.

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Rooks, B. (2002), “Rapid tooling for casting prototypes”, Rapid Prototyping Journal, Vol. 22 No. 1, pp. 40-5. Song, Y., Yan, Y., Zhang, R., Lu, Q. and Xu, D. (2001),

Further reading Marutani, Y. and Kamitani, T. (2004), “Manufacturing sacrificial patterns for casting by salt powder lamination”, Rapid Prototyping Journal, Vol. 10 No. 5, pp. 281-7. Corresponding author Dr. A. M. Kuthe can be contacted at: [email protected]

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