Research On Feature Based STEP Modeling For The Integration Of CAD/CAPP/CAM

With the wide use of CAD CAPP and CAM systems in manufacturing industry, it becomes a problem to be solved imminently to integrate and share the information among the three systems. To solve the problem, there are two main tasks: one is to create a product model, another is to define a product data exchange standard. The product model should contain the information that needed during the integration of CAD CAPP and CAM, and the product data exchange standard ensure the information share among CAD CAPP and CAM systems. The combination of the feature based technology and the new product data exchange standard, so called STEP, provides a feasible method to create such a model.First, the author introduces some present product data models including wire frame model, surface model, solid model, and feature model, and some related product data exchange standards including IGES, PDDI, PDES, and STEP. The characteristics and shortages of the product data models and the product data exchange standards are analyzed in general. Aiming at the shortage of material information, tolerance information, technical information, and so on in the model, the author conducted a research on a STEP based and feature oriented method to integrate the information in the model. The models for several common features were created. They are hole feature, planar face feature, outer-round feature, planar pocket feature, revolved groove feature, circular pattern feature, and rectangular pattern feature. The paper also uses STEP standard to express information of some familiar features just as hole feature, planar face feature and so on. These models are all expressed in EXPRESS language. These models consist of geometric information, tolerance information, process routing information, fixture and jig, tooling method, and material information. At last, the author developed a proto type system, which can extend the Pro/E generated neural STEP file through adding the additional information such as tolerance, process routing, and so on. The extended STEP model can automatically generate a feasible process plan to realize the seamless integration of CAD/CAPP.