The shell moulding process is a precision sand casting process capable of producing castings with a superior surface finish and better dimensional accuracy than conventional sand castings. These qualities of precision can be obtained in a wider range of alloys and with greater flexibility in design than die-casting and at a lower cost than investment casting. The fundamental feature of the process is the use of fine-grained, high purity sand that contributes the attributes of a smooth surface and dimensional accuracy to moulds cores and castings alike. In conventional sand moulding the use of such fine sand is precluded because it would dramatically reduce mould permeability.
A further improvement in casting accuracy can be obtained if zircon sand is used instead of silica sand. That arises because the expansion of zircon sand, caused by the heat of the cast metal, is both lower and more predictable than that of silica sand. Foundry production of castings by the process is comparatively straightforward and the process lends itself readily to close control, with the advantage of consistency in the castings produced.
Typical applications include crankshafts, camshafts, oil & gas parts and general engineering