Tool Path Planning In NC Machining Of Free-Form Surface

Along with the rapid development of the manufacturing industry, more and more free-form surface are used in aviation, automobile, shipbuilding and electronic products, and so on. Such as aerodynamics airplane outline, automobile body, turbine paddle blade and handset outer covering, and so on. Because of the design of these products become more complex, resulting in products processing more difficult and time-consuming. Therefore, how to improve the processing efficiency and accuracy of these special products become the problem to be solved, while NC machining technology to these free-form curves and surfaces is one of the key technologies to these industrial products manufacturing. In recent years, with the continuous progress of the technology and the quality requirements improvement of these industry products their own, higher demand of NC processing technology and tool path design to a free form surface is put forward in the processing and manufacturing industries, and more and more people begin to study that.Tool path planning is one of the key technologies to be resolved in the complex surface machining process, it's rationality is directly related to the possibility of maximum processing efficiency within the error allowed. Firstly, based on the NURBS surfaces, the CC point and the CL point during the NC machining was calculated in this paper making use of iso-scallop methods. Secondly, according to the distribution character of the CL points, a new approximate arc length method to parameterize CL point data and structure nodes vector was presented. Thirdly, the initial set-up and adjustment method about the number and position of control culmination during the NURBS fitting optimization calculation was given, and the two-step optimization high-precision fitting method is put forward based on NURBS tool path generation demand.In addition, machining simulation to a free-form surface using linear interpolation tool path and NURBS curves tool paths was given in the paper. It is proved that NURBS curves tool paths can greatly enhance the size accuracy and the geometry accuracy during NC machining of free-form surface, improve surface roughness and the smoothing of the surface, and also can reduce the workload of surface follow-up polishing, can meet the needs of high-performance CNC machining on free-form surface very good, and possesses highly theoretical value and engineering significance.