Research On Tool Path Optimization Of Five Axis NC Machining Based On Equal Residual Height Method

Five axis CNC machining center has become the only way to process complex curved surface parts such as impeller,blade,propeller with its high precision,high degree of freedom,high degree of automation.it is widely used in aerospace,ship manufacturing,automobile manufacturing,mold manufacturing and other industries,providing a huge boost for the development of national industry.Tool path planning based on 5-axis NC machining,as the core link from complex surface design to complex surface machining,has an important impact on the quality of the finished products of complex surface parts,and has been a hot and difficult topic for experts.Firstly,this paper systematically analyzes the development process,main classification methods and future development direction of five axis CNC machine tools.Then,the modeling method and differential geometry characteristics of NURBS complex surface are introduced.At last,the planning principle of the method is studied deeply,and the step accumulation error elimination algorithm for step length accuracy optimization is proposed,and the mutation point elimination for fairing path generation is also proposed methods,for the spiral path generation method of high machining.Good results have been achieved through simulation verification,which effectively improves the machining accuracy,machining efficiency and workpiece surface quality.The specific research results and innovations of this paper are as follows:(1)A tool path planning method with high precision step length is proposed.The basic principle of the method of analyzing equal residual height,and according to the step length of the adjacent trace line,the processing line distance,the direction of the short path line and other information,the calculation formula of the step length between the corresponding tool contacts on the offset trajectory line is deduced.And further analyzes the general rule of the step length change under the condition of the path smoothness.It is found that when the equal residual height method generates the smooth path,the step length will generate cumulative error The results show that the actual step size deviates from the theoretical step size seriously and reduces the machining accuracy.According to the actual step size and the theoretical step size,the concept of step size error change rate is proposed.The step size cumulative error elimination algorithm is designed to control the step size error in the offset trajectory line.Finally,the simulation results verify the correctness of the step size cumulative error theory and the rationality of the step size cumulative error elimination algorithm.(2)A tool path planning method for fairing path generation is proposed.There is a serious dependence between the trajectory lines generated by the equal residual height method,sometimes it will cause the following offset trajectory lines to appear mutation points,inflexion points,self intersection,etc.,which will bend the trajectory lines and seriously affect the smoothness of the trajectory.This paper analyzes the position relationship between the cutting direction and the follow-up cutting trajectory,puts forward a method to determine the mutation points,inflexion points,and combines the regulations of the equal residual height method Based on the principle of scribe,the method of eliminating abrupt point and inflection point is put forward.The simulation results show that the method proposed in this paper can completely eliminate the abrupt point and self intersection phenomenon in the path line,generate smooth tool path,effectively improve the machining accuracy and ensure the surface quality of the workpiece.(3)An equal residual spiral path planning method for high speed machining is proposed.The equal residual spiral path combines the advantages of the equal residual height method,such as high machining efficiency,equal residual height of the workpiece surface,and less tool empty travel and stable tool load.It is very suitable for high machining.In this paper,the equal residual spiral path planning algorithm is designed based on the equal residual smooth path generation method to generate the smooth equal residual spiral path The simulation results show that the total length of the trajectory line and the number of turning angles of the equal residual spiral track are better than that of the equal parameter spiral track,which can effectively improve the processing efficiency.