Accuracy issues in rapid manufacturing CastForm™ patterns

Abstract

Selective laser sintering (SLS) or laser sintering (LS) is a very popular layer manufacturing technique extensively used to produce concept models, functional parts, cores, and cavities for different types of moulding tool, and also patterns for investment casting. CastForm™ polystyrene (CF) is a material used for fabrication of investment casting patterns employing the SLS process. The use of the CF material is one of the fastest and most cost-effective manufacturing routes to produce small-quantity wax-like patterns for shell or flask investment casting. Unlike other materials suitable for LS, the manufacture of CF casting patterns is done in two stages. The first is the building of a ‘green’ part and the second is its infiltration with wax. The accuracy of the patterns, and ultimately the final accuracy of the metal castings, is determined by the CF properties and the applied process parameters. The factors affecting the accuracy of the CF patterns are investigated in this paper. In addition, different ways to improve the process accuracy are discussed. An analysis of advantages and limitations of this manufacturing route for producing patterns for investment casting is provided.