Shell Mould Casting

Shell mould casting is also known as shell moulding.

Shell mould casting has grown significantly because it can produce many types of castings with close dimensional tolerances, good surface finish and at a low cost.

It is used for small to medium parts that require high precision.

In this process, a mounted pattern made of a ferrous metal or non-ferrous metal heated to 448K to 643K.

Most commonly pattern materials are casting iron, carbon steel, alloy steel, stainless steel, aluminium alloys & copper alloys.

Parts are made using shell mould casting such as gear housings, cylinder heads, connecting rods & lever arms.

Figure:- Steps involved in shell mould casting

Steps involved in shell mould casting are:-

Step-1 A metal pattern is heated and placed over a box containing sand mixed with thermosetting resin.

Step-2 Box is inverted so that sand and resin fall onto the hot pattern, causing a layer of the mixture to partially cure on the surface to form a hard shell.

Step-3 Box is repositioned so loose uncured particles drop away. Depending upon the time and temperature of the pattern, the thickness of the shell is 10 to 20mm.

Step-4 Sand shell is heated in an oven for several minutes to complete curing.

Step-5 Hardened shell is then stripped from the pattern.

Step-6 Two halves of the shell mould assembled via clamping or glueing using a thermoset adhesive, to form a mould, supported by sand or metal shot in a box, and pouring is accomplished.

Step-7 Finished casting is removed.

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