Tool-path Programming Based On Reverse Engineering In NC Machining

Geometry model and generation of cutter path are two key technologies for NC machining. In the two technologies, geometry model is the base for calculating cutter path and the accuracy of NC machining only depends on the rational cutter path. The appropriate planning of cutter path not only direct influence stock-removing efficiency, machining precision and machining interference but also influence the dynamic performance of machine tool and operating life of cutter.At present, tool-path programming is accomplished by manual man-machine alternation completely and excessively depends on the experience of engineers. The diversified processing parameters and the engineering data also depend on handbooks and experience of engineers, and the automatization can not be achieved.Based on the need of actual production, the paper studies a master piece which comes from Haise microbus made in Shenyang Brilliance Jinbei automobile limited corporation aiming at the tool-path programming of free surface.Based on the theory of reverse engineering and three-CMM, the paper gathers many data from the free surface of the sample part and gains points cloud. With Imageware software, the noise points is eliminated. Then, free surface is formed by reconstruction technique.The dissertation studies the feed pattern of free surface deeply, including linear feed pattern, circular feed pattern and gyroidal feed pattern, and the linear feed pattern is emphasis. Aiming at high machining efficiency, the mathematical model of time is founded on the base of accelerate or decelerate of changing line and smooth speed in the course of machining. Using C++ Builder software, the program of mathematical model, is worked out. It can read the source file of cutter position from commercial CAD/CAM software and calculates machining time of tool-path. Ultimately, the auto-optimization of cutting orientation is achieved.Aiming at rough machining, the paper founds tool-path programming system and makes computer have the capability of intellective discursion, makes free surface to be regular and auto-optimizes tool-path according to the character of shape and technics.Tool-path programming system will make up the disadvantage that the commercial CAD/CAM software excessively depends upon engineer. This founds the base of making CAD/CAM software homemade.