Tool path generation for rough machining using STEP

The production efficiency has been significantly improved over the years due to the rapid advancement in CAD and CAM. Very often, however, the production cycle is still unacceptably long. This has been frequently caused by the bottleneck link between CAD and CAM. The CAD design model cannot be directly machined by a CNC machine without an NC program, an NC program cannot be coded without a clearly defined tool path, and the CAD data are not readily useable for preparing tool path. A large amount of time is often spent on data exchange, NC tool path generation, and NC program preparation. To further reduce the production cycle, the CAD model has to be documented in a neutral format such that it can be readily used in CAM and the tool path should be automatically generated from the CAD model in a neutral format. The recently developed STEP data exchange standard provides such a neutral format that is independent of any software and hardware. However, none of the existing tool path generation systems is based on STEP.;In view of the above facts, a STEP based tool path generation system is developed for rough machining of planar surfaces. This system comprises four modules. The first one is the data extraction module used to obtain geometric data from STEP. The second module is the slicing module which is designed to convert the three dimensional tool path generation problem into a series of two dimensional problems. The tool path will be generated by the third module. The tool path is then translated into NC program by an NC code generator--the last module.;The proposed system has been implemented in a UNIGRAPHICS CAD/CAM environment. The application of the system is illustrated using an example part.