An approach to eliminate shell cracking problem in fused deposition modeling pattern based investment casting process

Abstract

Fused deposition modeling process can be used to make complex plastic parts directly from the three dimensional CAD drawings without any requirement of tooling. For low volume production, these plastic parts can be used instead of wax patterns in investment casting process to reduce high cost of tooling required for making wax patterns. But with plastic patterns there is a problem of ceramic shell cracking during the pattern burnout process. This shell cracking is mainly due to thermal expansion of the plastic sprue and plastic patterns. In this paper, a method has been proposed to eliminate the problem of shell cracking by using a wax sprue instead of plastic sprue. A joint has been designed to attach plastic patterns with wax sprue. It has been found that the proposed method is successful in eliminated the shell cracking problem. In addition to this, the proposed method is expected to reduce the process cycle time and cost.