A New Approach to Mold Design Using Manufacturable Entities

Abstract A new approach using two process specific entities is presented for generating the shape of the mold for an injection molded part simultaneously as the part is being created. The user creates the part, and the mold is generated dynamically and transparently to the user. The mold is created using six stages of analysis; (1) the part is analyzed for undercuts based on the accessibility of the entities from the bottom most plane of the part to determine if the mold is either a two piece or a multi piece mold; (2) the number of mold pieces is determined from the number of undercuts and their locations; (3) the parting direction and the parting line for each mold piece are determined from the properties of a rectangular box surrounding each entity in the mold piece (called an extent) and from the properties of a vector field normal to the parting line; (4) the stock size is determined for each mold piece from the properties of the extents; (5) the process plan for machining each mold piece is determined; and (6) the complete mold is created by assembling all the mold pieces. It is demonstrated that using process specific entities simplifies the different stages of mold creation process. Furthermore, generating the process plan for each mold piece requires only arranging the entities to be machined in each mold piece based on their accessibility from the surface of its stock. It is demonstrated that by creating the mold incrementally after each stage of a part’s creation allows one to perform manufacturability evaluation of the part and the mold simultaneously. The advantages of our approach over the current methodologies for determining the mold from the part are enumerated.