A hybrid approach for automatic parting curve generation in injection mold design

Abstract

Automatic parting curve generation plays an important role in the realization of automatic injection mold design. We propose a hybrid visibility-based and graph-based approach to generate the parting curves of a solid part automatically. The approach consists of three steps: (i) construct a graph representation of the solid part, (ii) recognize mold piece region, and (iii) generate parting curve. In step (i), the surface visibility and edge convexity-concavity are attached to the graph. Visibility determination algorithms for various surface types and edge convexity-concavity calculation methods are also discussed. In step (ii), part surfaces are classified into concave-edge regions, inner-loop regions, and isolated surfaces. Concave-edge regions are decomposed into sub concave-edge regions based on graph-based algorithms that have linear time complexity. Concave-edge regions, inner-loop regions, and isolated surfaces are assessed to extract the cavity region, core region, and undercut regions. In step (iii), the boundary edges of each region are extracted to form parting curves. The approach has linear time complexity and is effective for complex solid products with planar surfaces, quadric surfaces, and free-form surfaces. Finally, two case studies are provided to validate the proposed approach.