The metal pattern is first heated at a temperature of 200 0 C / 392 0 F.Then covered with a mixture of sand and thermo set plastic. It forms a skin of sand/ plastic mixture of about 3.5 mm (0.125 inch) which adheres to the pattern. The shell mould is formed after the skin gets removed from the pattern.
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The two halved of the shell mould are secured together and the metals id poured in the shell to form the part. Once the metals solidified, the shell is broken. |
Features of Shell mould Casting:
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Good Surface Finish : 1.25µm to3.75µm (50µin to 150µin)rms dimensional To- |
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-lerance of 0.5 % |
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Size Limits : 30 g to 12 kg (1 oz to 25lb) |
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Minimum Thicknesses : As low as 1.5mm (0.062 in) to 6.25mm (0.25 in) de- |
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-pending on the material |
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Superi or Machining Qualities : As it has soft skins and hard or dense interiors |
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Draft Allowance : Typically 10 C |
Application:
The materials that can be used with this process are aluminum, cast irons, and copper alloys. Parts made can be connecting rods, Gear Housings, Lever arms etc.
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