Process planning and NC-code generation in manufacturing of press dies for production of car bodies

This paper presents a process planning system that generates process plans and NC codes for machining of press dies, which are used in manufacturing the body panels of cars. This system consists of three modules: a macro-process planning system that generates process plans for major parts of press dies; an operation planning system that generates operation plans and NC codes for free-form surfaces; and an NC-code post-processor that analyses and modifies NC codes. Fifteen major part-families (PFs), along with their standard process plans, are defined for macro-process planning. A process is a set of unit operations, which can be completed without changing the set-ups. Details, such as cutting tools, cutting conditions, and tool paths are decided upon during the operation planning stage. After generating cutter location (CL) files, using commercial CAM systems, the operation planning system selects cutting tools and their lengths to generate NC codes. At the final stage of process planning, the NC code post-processor adjusts feed rates along the tool path to reduce machining time while maintaining the quality. In order to adjust the feed rate, the machining load per each tool-path segment is estimated using virtual machining.