Compensation Of Tool Radius And Nonlinear Error For Five-axis CNC System In Shoe Last Machining

China is a big shoe-making country.Shoe lasts are the molding molds for making shoes,the demand is huge.With the advancement of processing technology,the shoe last has realized five-axis CNC machining,and the processing efficiency and quality have been improved.However,the machining error is inevitable in the actual machining because of the working mode of the five-axis CNC system and the characteristics of the machining itself.These errors include the dynamic error of the machine axis when the feed rate and acceleration of the motion axis exceed the allowable value of the machine during the speed planning,the tool error caused by the tool wear during machining,the thermal deformation error of the cutter and the workpiece,and the nonlinear error caused by the rotating axis,etc.This paper mainly studies space cutter radius compensation and nonlinear error compensation.The main work of this thesis is to study the five-axis CNC system of shoe last,and to explore the feasible compensation method of tool radius wear error and nonlinear error.The main research contents are:(1)Solution of cutter location data.Process the existing NC program,and the displacement information of the B rotating axis is converted into angle information according to the B-axis structure;The kinematics forward transformation and kinematics inverse transformation are solved according to the structure of the five-axis CNC machine tool used in shoe last machining;The program is written by Matlab to realize the conversion from the NC code to the cutter location data.(2)Proposal and implementation of toroidal cutter radius compensation method.In the NC program,the information of cutting contact point and its normal vector information have been lost,which brings great difficulty to the solution of the cutter radius compensation direction.This paper proposes a feasible way of cutter radius compensation in the case where the cutting contact points are unknown,and it is realized by Matlab.The Vericut simulation and experimental verification of the NC program compensated by this method are carried out,which proves the feasibility of this method.(3)Analysis of nonlinear error and the proposed control strategy.The nonlinear error is a principle error caused by the inconsistency between the linear interpolation and the rotation axis of the five-axis CNC system.Firstly,the generation mechanism,calculation,influencing factors of nonlinear error and the location of maximum nonlinear error are analyzed.On this base,this paper proposes a nonlinear error control strategy.Matlab is used to simulate the tool path trajectory before and after applying the control strategy,and the error values are compared.The effectiveness of the algorithm is verified.