Design automation of two-stage collapsible core using design prototype

Internal features such as undercuts in plastic products obstruct the remova l of the moulded product and so special moulding tools have to be custom-de signed. Since there is a lack of design knowledge of such tools, heuristic knowledge has first to be formalised and then organised into a framework so that die design can be automated. This paper discusses how a functional re asoning approach for the design of a two-stage, lever-actuated collapsible core for the moulding of uPVC pipe fittings with internal undercuts was imp lemented as design prototypes that were subsequently computer-automated. In functional reasoning, a design is represented in a hierarchy of functions and the behaviours that realise the functions. A structure contains specifi c variables such as the way in which the design should be assembled. Four d ifferent types of knowledge bind together function, behaviour and structure . These are relational, qualitative, computational and context knowledge. T he design prototype for the collapsible core was implemented in UniGraphics II. The time required to design these moulding tools has been drastically reduced in the plastic injection moulding company with whom this research w as jointly undertaken.