Hollow shape extraction: geometric method for assisting process planning of mold machining

In the mold part machining, rough milling with large cutters is applied first to efficiently remove excess material, then milling operation with small cutters finishes the mold surface. Large cutters cannot remove sufficient material at hollow shapes of the mold, therefore manufacturing engineers must apply some additional milling operations with medium size cutters prior to the finishing. Process planning of such semi-finishing operations, especially determination of the milling region with large remained material is currently done based on a manual extraction of the hollow shape using the machine drawing. In this paper, the authors propose an algorithm for automating the hollow shape extraction. This algorithm uses the inverse offset computation and milling simulation in the process, which are known very time-consuming. In order to boost the computation speed, the rendering hardware based acceleration technology is introduced. Proposed algorithm is implemented and an experimental system for assisting the process planning of the semi-finishing operation is demonstrated.