PARTIAL VISIBILITY FOR SELECTING A PARTING DIRECTION IN MOLD AND DIE DESIGN

Selection of an optimal parting direction in mold and die design is co nsidered. Based on the condition for demoldability, two levels of visi bility-complete and partial-are defined for a surface. If a surface is completely visible along a certain direction, it can be separated fro m the mold along the opposite direction. If a surface is not completel y visible and therefore cannot be separated from the mold along any di rection, it can be decomposed into two portions: those that are separa ble and those that are undercuts; the former is based on complete visi bility and the latter on partial visibility. Algorithms are given for computing the undercut volumes of a polyhedral surface with respect to a particular parting direction and for selecting a parting direction that minimizes the number of undercuts.