Epoxy-copper composite materials for injection molds optimal design: a low-run production simulative study

Abstract

Mold injection is an expensive manufacturing method, it involves several engineering-design hours and expensive alloys. Enabling the use of low cost mold tooling can turn low-run productions economically and sustainably viable. There is a low-cost and more environmentally amicable alternative to injection molding for low-run productions based on epoxy resin molds. However, one drawback is the polymeric nature of the epoxy material, which possess low thermal conductivity, negatively affecting the injection process and thus quality of the molded pieces; as well as its low degradability rate. An opportunity arises for improving the performance of epoxy resin molds by studying the effect of embedding thermally conductive fibers in the matrix. Methodology used in this work consisted in the computational evaluation of a series of molds of composite materials models built up from epoxy resin and copper fibers in different geometrical shapes and orientations. Injection simulations were carried out using software Moldflow and the “effectiveness” of the injected parts was assessed (i.e., injection cycle time, % volume shrinkage and injected part deflection). Results suggest that embedding copper fibers within the epoxy matrix resin molds lowers the injection cycle time, reduces volumetric shrinkage while maintaining the deflection amplitude of the injected parts; optimum effectiveness results were obtained when copper is embedded as long fibers oriented along the principal heat flow direction. Moreover, epoxy resin can be replaced by up to a 70 % volume of copper fibers, depending upon wall thickness