Application of Catmull-Clark subdivision method in plastic injection mould parting surface design

Automation of the various tasks of the plastic injection mould design process has attracted a lot of attention. Techniques for the automatic selection of parting direction, determination of the complex 3D parting line and the generation of parting surface have been reported. A common strategy in parting surface generation is the method of extrusion. Our investigation reveals that this method fails under certain conditions, which results in intersection between the parting surface patch and the part surface, and inter-locking between the mould halves. To solve these problems, a new method based on the subdivision method of surface generation is proposed. A variation of the Catmull-Clark subdivision scheme is employed which ensures that the resulting surface interpolates the main parting line of the part. The initial control mesh used in the subdivision process is obtained by "projecting" the 2D medial axis of an approximating polygon to 3D. An experimental program has been implemented to verify the feasibility of the method.