Automated assembly modelling for plastic injection moulds

An injection mould is a mechanical assembly that consists of product-dependent parts and product-independent pairs. This paper addresses the two key issues of assembly modelling for injection moulds, namely, representing an injection mould assembly in a computer and determining the position and orientation of a product-independent part in an assembly. A feature-based and object-oriented representation is proposed to represent the hierarchical assembly of injection moulds. This representation requires and permits a designer to think beyond the mere shape of a part and state explicitly what portions of a part are important and why. Thus, it provides an opportunity for designers to design for assembly (DFA). A simplified symbolic geometric approach is also presented to infer the configuration of assembly objects in an assembly according to the mating conditions. Based on the proposed representation and the simplified symbolic geometric approach, automatic assembly modelling is further discussed.