Design for manufacture: An integrated system for injection molding and milling

A novel approach to an integrated design for manufacture system is presented in which manufacturability analysis is performed concurrently in two domains, injection molding and milling, using complementary process specific entities. This new approach uses a fundamental manufacturing entity for milling (FMEM) to create and to evaluate the manufacturability of the mold by milling and a C-entity, which is the complement of the FMEM, to create and evaluate the manufacturability of the part for injection molding. It is demonstrated that by using the FMEM and the C-entity one can perform manufacturability evaluation of a part and its mold without either feature extraction or designing with features. This new approach also eliminates the need for converting features from one manufacturing domain to another, and uses a single uniform data structure to represent the shape characteristics of parts made in the two manufacturing domains. Since all the shapes are represented in the same manner, the manufacturability evaluation of the part and its mold is reduced to a small set of algorithms based on an evaluation of only the entity's profile and the pair-wise interaction with other entity profiles.;The user creates the part for injection molding by assembling C-entities. The manufacturability evaluation is performed after every C-entity is created and after a C-entity is assembled with any of the previously created C-entities. The system determines the shape of the mold transparently to the user. The part is represented as an M-digraph to determine either the two-piece mold or the multi-piece mold. In addition, a new methodology has been introduced to determine the shape of a two-piece mold such that the parting lines of the part lie along its natural edges. It is demonstrated that using process specific entities simplifies the different stages of the mold creation process, and that the generation of the process plan for each mold piece requires the sequencing of the entities in each mold piece to be based only on their accessibility from the surface of its stock. It is further 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 system can also be used to create a part for milling by subtracting a user-created set of FMEMs from a rectangular prismatic stock. Manufacturability evaluation is done after creating each FMEM and after placing and subtracting the FMEM from the stock. A new approach to determine an integrated process and fixture plan for the part is presented. The fixturing requirements for machining each FMEM are identified after each FMEM is created and subtracted from the stock. The fixturing configurations are analyzed to determine whether or not the machining operation interferes with the vise. A new methodology using volume and surface grids to identify the part surfaces that are suitable for being held by a parallel-jaw vise has been developed. This methodology is implemented in tandem with the process plan generating algorithm to eliminate those process plans in which a part cannot be held for any of its machining operations.