Tool Path Planning For High Speed Milling Of Free-form Surface With Toroidal Cutter

High-Speed Cutting techonology of Free-form Surface has become a core techonology in manufacturing with the increasing use of Free-form Surface in space flights, aviation, automobile and mold.Meanwhile, the users demand for better industry products, that makes highly demands for NC techonology and Tool path planning techonology.Tool path generation directly affects the precision,surface roughness,processing time and cutter life,directly determines the productivity.Therefore,Tool path planning techonology can get the most benefits out of CAD/CAM.Domestic and overseas scholars have done a great deal of research on Tool path planning for High Speed Milling of Free-form Surface,it is one of hotest research field in scientific and technological circles。This article did some research on Tool path planning for High Speed Milling of Free-form Surface with Toroidal Cutter,The main work and achievements are summarized as follows:1. Studied the tool path planning theory domestic and abroad,analyzed the isoparametric method, curves of cross sections method, polyhedron cutter planning method,iso-scallop method,we can conclude that,iso-scallop method has higher efficiency and better machining effect.But the iso-scallop method's cutter-orientation lack of flexibility while machining,In traditional method,the angle between cutter axis orientation and surface normal vector keeps invariant,keeping3-10°, cutter axis orientation's determination without geometric analysis, it is blindness.Although,the iso-scallop method's can improve the Five-axis NC machining efficiency,but it doesn't fully reflect the superiority of Five-axis NC machining,also it may cause interference and tool over-cutting,need a great of human intervention.So,the tool path planning for High Speed Milling of Free-form surface,proceed in two major areas : First , aiming at the Free-form surface , optimization in step size and row spacing;Second,aiming at the cutter, optimization in cutter axis orientation.Base on the consideration above,this article use a new row spacing formula ,which proposed by Zhang Ying,Zhang Dinghua,Wubaohai,Northwestern Polytechnical University:That is, take formula(1) which determined by heel angleλand side slip angleω,into formula(2) that derived form iso-scallop method,put forward a new algorithm,called self-adaptative tool path and cutter axis orientation iso-scallop method based on principal curvature matching, its main advantages is the avoidance of local interference,also it can obtain the maximum row spacing and heel angleλand side slip angleωfor the different CC-Point, give full play to the advantages of Five-axis NC machining,and avoid wasting the machining capability of Five-axis NC machine.2.In order to demonstrate the accuracy and the efficiency of algorithm presented by this paper,some simulations are presented by MATLAB,and compared with the tool path generated by iso-scallop method, as the results shown by fig.1.We can see from fig.1, the row spacing generated by this method are wider then the iso-scallop method, at the same time, it also calculated the cutter-orientation(heel angleλand side slip angleω) that avoid the local interference. Also we can see from tab.1, that the tool path generated by this method has reduced 24.39% compared with the iso-scallop method, and path length has reduced 18.72% compared with the iso-scallop method,the result shows that the improved algorithm presented in this paper increases the efficiency of machining and improve the quality of machining.3.This paper also did some research on feed rate feed post-processing method ,such as formula(3),calculated the constant surface feed rate,that is under the condition of the same feed rate,compare with the coordinate axis component of the feed rate of the two methods. The simulation results are shown as follows: fig.2 translational axis rate generated by this method(the second tool path) fig.3 translational axis rate generated by iso-scallop method (the second tool path)Derivation of the velocity curve,obtained the acceleration curve,figure 4 and figure 5. Compared with the four figuers above,we can conclude that if adopt the traditional iso-scallop the X translational axis rate-Vx is unstable,the acceleration change greatly, but the X translational axis rate-Vx and acceleration curve change mildly that generated by this method,it means the milling force change stable, could reduce vibration shock and noise,prolong the tool life,improve the surface quality and machining effiencf. To speak volumes for the difference of the two algorithms,several tool paths is simulated in the paper,because of the paper length,so not enumerate the figures one by one here.By means of geometric simulation and physical simulation,the results shows that the algorithm presented by this paper improved the quality of the tool path of the programming system, increased the efficiency of machining and improved the quality of machining.