The Tool Path Planning And Simulation Of 3-D Integral Impeller In NC Machining

Currently,the complex surface machining is a hot research in the field of mechanical manufacturing. It's no doubt that impeller parts have already become a typical representative in complex surface and are widely applied in some important fields of the national economy. The impeller design involves many disciplines such as aerodynamics, fluid mechanics and so on. The impeller machining method, machining precision and surface quality exert great influence on aeroperformance. This paper mainly touches on the five axis NC machine-oriented machining method of integral impeller.Tool path plan,computation method of tool path as well as tool path simulation are the core contents of the paper.Impeller model is generated by calling related function,after analyzing geometry model of the impeller deeply and integrating the related knowledge of complicated surface modeling, such as the technology of B-spline curve fitting, VC++ and OpenGL etc.In the process of the rough machining, the rough is milled in terms of layered strategy, and the tool path is planned by zigzag. The shortest distance between two blades is obtained by computing the distance from point to surface. Meanwhile, a comparative analysis between this distance and the result measured in UG is conducted. Cutter central point of every layer is identified by computing midpoint in a circle, and the cutter axis vectors are acquired by subtracting the cutter central points in bottom layer from the cutter central points in top layer.After that, the finish machining tool-path of the blade and the cutter axis vector are obtained by use of both double-points offset algorithm and the method of intersection of the cutter axis and offset hub surface. This paper not only calculates the geometrical residual error of every tool path with the method of computing the shortest distance from point to surface, but also analyzes the distribution of the geometrical residual error deeply. In the light of the rationale of the double points offset, the previous tool path can be optimized. At last, the less error and reasonably-distributed finish machining tool path is nailed down.By application of computer simulation technique, OpenGL and simulate dynamic variation of cutter during the machining, the interference of the previous tool path is checked and the whole accessibility of curved surface is judged. Finally the reasonable and optimized project is obtained before machining. The result reveals that the combination of theoretical analysis and simulation technique is an effective approach to verify the tool path of complicated surface in NC machining.