An investigation into the rapid prototyping of moulds for expanded polystyrene foam

Expanded polystyrene foam, a packaging material, is traditionally injection-moulded by classical moulding techniques. However, the design and fabrication of these moulds is both intricate and time-consuming. In today's manufacturing environment of short time-to-market, the luxury of producing a mould for, often, a first-off article for client approval, is virtually untenable. Rapid prototyping technologies appear to offer an alternative method of fabrication which promises to drastically reduce the time for mould fabrication. When rapid prototyping of the mould is combined with microwave curing of the polystyrene, as an alternative source of energy to traditional steam heating, the benefit of considerably short throughput times can be expected. This paper describes the computer-integrated design and fabrication of both the mould and foam product, and discusses the main issues associated with rapid prototyping the mould, viz. accuracy of the prototype mould and the suitability of acrylic resin used in stereolithography apparatus for fabricating the mould, as well as the parameters for moulding expanded polystyrene using microwave energy. Initial results suggest that both the stereolithography process, and the acrylic resin used to build the stereolithographic model, can be used for rapid prototyping expanded foam products and their associated mould.