Design of internal pins in injection mold CAD via the automatic recognition of undercut features

A methodology to deal with the automatic design of internal pins in injection mold CAD via the automatic recognition of undercut features is developed. The approach to automatically identifying the undercut features is first proposed. For the given parting directions, all the inner and outer undercut features are identified based on the topological relationship of geometrical entities. The outer edge loop, which represents the largest cross-section boundary along the given parting directions, is extracted and patched up. The surfaces of molding are then identified based on the classifications of their geometrical entities. To identify the deep inner undercuts in the molding, the projection of the main core, internal pins and their bounding boxes along the parting direction and the pin withdrawal direction are generated. Upon determination of whether the bounding boxes of any two internal pins and the main core projection have intersection area, the deep inner undercuts are located. The complete methodology is finally implemented and verified through case studies and the efficiency of the methodology in handling complex molded parts is thus illustrated.