Feature extraction from freeform molded parts for moldability analysis

Abstract

In the design of plastic injection molds, the depressions and protrusions (DP) preventing the removal of molded part from mold are referred to as undercuts. This paper describes an approach to recognize DP feature within the curvature region representation based on the curvature properties of entities in B-rep model. The recognized depression features and the concave transitions between protrusion features are potential undercuts which affect the choice of parting directions of the molded part. The possible withdrawal directions of the potential undercuts are derived by geometric reasoning and visibility map computation. This method can recognize isolated and intersecting features with planar, quadric, and freeform surfaces. The identified potential undercuts with their possible withdrawal directions can provide decision support information for mold design such as selecting parting direction, parting lines and surfaces, etc. The case study is presented to verify the feasibility of the developed method.