The effect of mould heating on the accuracy of rapid tooling

The inherent technical limitations of rapid prototyping systems have lead to the development of rapid tooling techniques. These techniques allow manufacture of prototypes in final materials by the final manufacturing process. Enhanced silicone moulding is one such process that provides both a rapid and low cost route to the manufacture of prototype injection moulded plastic components. During the moulding cycle, the mould deforms due to the high pressures and temperatures experienced. This results in the manufacture of dimensionally inaccurate components. The main contributing factors have been identified as global expansion due to heating and local deformation due to injection pressure. This paper reports on the development of a model to predict the effects of mould heating. Two routes are reported, one using conventional analytical techniques and one using an approximated finite element technique. The validity of the models are assessed by comparison with experimental results.