Automatic generation of mold-piece regions and parting curves for complex CAD models in multi-piece mold design

Multi-piece molding technology is an important tool in producing complex-shaped parts that cannot be made by traditional two-piece molds. However, designing multi-piece molds is also a time-consuming task. This paper proposes an approach for automatic recognition of mold-piece regions and parting curves for free-form CAD models. Based on the geometric properties of objects and mathematical conditions of moldability, a collection of feasible parting directions is formed from which the sets of visible-moldable surfaces are identified for each parting direction. Moldable surfaces that are partially visible to a particular parting direction are recognized and divided into fragments by silhouette detection and edge extrusion. A set of criteria is proposed to arrange tentative fragments, which can be simultaneously visible to several parting directions, into appropriate regions for mold pieces. Finally, the parting curves for mold pieces are extracted from the corresponding mold-piece regions. The proposed algorithm overcomes the problems found in previous multi-piece molds and at the same time achieves high accuracy and high performance. Examples of industrially complex models are used to demonstrate the performance and robustness of the proposed algorithm. The approach is generic in nature, allowing its application to be extended to any complex geometry in 3-D mold design.