【正文】 of Injection Mould Assemblies The two key issues of automated assembly modelling for injection moulds are, representing a mould assembly in puters, and determining the position and orientation of a product independent part in the assembly. In this section, we present an objectoriented and featurebased representation for assemblies of injection moulds. The representation of assemblies in a puter involves structural and spatial relationships between individual parts. Such a representation must support the construction of an assembly from all the given parts, changes in the relative positioning of parts, and manipulation of the assembly as a whole. Moreover, the representations of assemblies must meet the following requirements from designers: 1. It should be possible to have highlevel objects ready to use while mould designers think on the level of realworld objects. 2. The representation of assemblies should encapsulate operational functions to automate routine processes such as pocketing and interference checks. To meet these requirements, a featurebased and objectoriented hierarchical model is proposed to represent injection moulds. An assembly may be divided into subassemblies, which in turn consists of subassemblies and/or individual ponents. Thus, a hierarchical model is most appropriate for representing the structural relations between ponents. A hierarchy implies a definite assembly sequence. In addition, a hierarchical model can provide an explicit representation of the dependency of the position of one part on another. Featurebased design [10] allows designers to work at a somewhat higher level of abstraction than that possible with the direct use of solid modellers. Geometric features are instanced, sized, and located quickly by the user by specifying a minimum set of parameters, while the feature modeller works out the details. Also, it is easy to make design changes because of the associativities between geometric entities maintained in the data structure of feature modellers. Without features, designers have to be concerned with all the details of geometric construction procedures required by solid modellers, and design changes have to be strictly specified for every entity affected by the change. Moreover, the featurebased representation will provide highlevel assembly objects for designers to use. For example, while mould designers think on the level of a realworld object, . a counterbore hole, a feature object of a counterbore hole will be ready in the puter for use. Objectoriented modelling [11,12] is a new way of thinking about problems using models organised around realworld concepts. The fundamental entity is the object, which bines both data structures and behaviour in a single entity. Objectoriented models are useful for understanding problems and designing programs and databases. In addition, the objectoriented representation of assemblies makes it easy for a “child” object to inherit information from its “parent”. References [1]. K. H. Shin and K. Lee, “Design of side cores of injection moulds from automatic detection of interference faces”, Journal of Design and Manufacturing, 3(3), pp. 225–236, December 1993. [2]. Y. F. Zhang, K. S. Lee, Y. Wang, J. Y. H. Fuh and A. Y. C. Nee, “Automatic slider core creation for designing slider/lifter of injection moulds”, CIRP International Conference and Exhibition on Design and Production of Dies and Moulds, pp. 33–38, Turkey, 19–21 June 1997. [3]. E. C. Libardi, J. R. Dixon and M. K. Simmon, “Computer environments for design of mechanical assemblies: A research review”, Engineering with Computers, 3(3), pp. 121–136, 1988. [4]. K. Lee and D. C. Gossard, “A hierarchical data structure for representing assemblies”, ComputerAided Design, 17(1), pp. 15– 19, January 1985. [5]. K. Lee and D. Gossard, “Inference of position of ponents in an assembly”, C