Study On Detection Of The Linkage Performance Relate To The Working Accuracy Of Five Axis CNC Machine Tools

The manufacturing industry is the backbone of national economy.As a foundation of various industry,CNC machine tool especially the five-axis CNC machine tool has been an important symbol of national production capacity and the level of automation.The linkage performance of five-axis machine tool is an important factor affecting the machining quality in the process of high speed and high precision machining.Therefore,it is important to detect the linkage performance of five-axis machine tool in improving the machining capability and machining accuracy.In this paper,the mechanism of the multi-axis linkage error in machining process is modeled to show the multi-axis linkage performance affecting the working accuracy of five-axis machine tool.The influence of servo control system performance on the multi-axis linkage precision and surface texture of the standard test piece is investigated to explore the efficient way to detect the linkage precision of five-axis machine tool.The linkage error tracing method is proposed to provide the guidance for the dynamic parameter adjustment.The corresponding relationship between the research content and each chapter is: In the second chapter,the linkage error model of the five axis machine tool is established according to the structure of five axis machine tool.In the third chapter,the mechanism of linkage performance of five axis machine tool in the formation of the local abnormal surface of standard test pieces is studied.In the fourth chapter,the principle of the linkage performance test of five axis machine tool based on RTCP is analyzed.In the fifth chapter,the linkage performance test trajectory of five axis machine tool is analyzed.In the sixth chapter,five axis machine linkage performance tracing method based on the detection of specific test trajectory is studied.The research contributions are as follows:(1)The internal relationship between the linkage performance of the machine tool and the surface texture of the workpiece is revealed.The waves related to the linkage performance of five-axis machine tool on the workpiece contour are analyzed based on the linkage error model of five axis machine tool.The unsmooth surface is extracted from the contour error by high pass filtering,and it is enlarged and superimposed upon the surface of the workpiece to show the surface texture at multiple positions of the workpiece.Simulation is presented,it is proved that the linkage error of five-axis machine tool is the main cause of abnormal surface quality of the workpiece.The standard specimen NAS979 cone test piece and S shape test piece are taken as the research objects.The geometric features and machining features of these two pieces are analyzed.S shape test piece has the advantages of varying curvature,quadratic discontinuity,and rich machining movement states.Through the simulation and cutting experiments of the standard pieces,the internal relationship between the surface texture and the linkage error of the machine tool is proved.For the same linkage performance of five-axis machine tool,the surface quality of S shape test piece is hugely worse than NAS979 cone test piece.And there are several special regions on S shape test piece to exhibit the imperfect linkage performance more directly and intuitively.Therefore,the detection for the linkage performance of five-axis machine tool based on the surface quality of S shape test piece could visually and effectively show the linkage performance and guarantee the machining capability and the machining accuracy.(2)A kind of RTCP detection trajectory,which is different from the ISO standard,is presented to show the linkage performance of the five-axis machine tool more effectively.Since the exhibition of the dynamic error of translational axis and rotary axis on tool tip error is different,the linkage performance detection of five-axis machine tool based on RTCP could evaluate the linkage performance of the five axis machine tool effectively.By analyzing the relationship between translational axis motion and rotary axis motion,the description of the RTCP detection trajectory with the rotational axis motion parameters is determined.The effects of the rotary axis motion parameters on the RTCP error pattern are analyzed.A description of the RTCP detection trajectory based on cosine function is proposed,which is different from ISO standard trajectory,and 4 cosine trajectories are proposed.The geometric characteristics,kinetic characteristics and the sensitivity of the tip point error on the linkage performance machine tool of the cosine trajectories and ISO standard trajectories are analyzed.Circular trajectorys2 T and 8 shape trajectorys3 T have advantages that there is the variety of curvature,the richer linkage velocity and the higher error sensitivity.The sensitivity is selected as the object function of the optimum design,the RTCP detection trajectory is optimized by genetic algorithm,and three optimal trajectories: s3 T trajectory,345 sT trajectory and 390 sT trajectory are proposed.The simulation and experiments are carried out to verify the superiority of the RTCP optimized detection trajectories in the linkage performance detection ability of five-axis machine tool.(3)A method to trace linkage error of five-axis machine tool based on image recognition and trajectory similarity is proposed.The tool tip error trajectories of 8 shape trajectory s3 T is used as the object,the linkage errors is divided into 75 categories by the difference of the tool tip error trajectories in serious linkage performance states.The characteristic parameters from normalizing tool tip error trajectories are extracted based on the Fourier Descriptor.The linkage error type of five axis machine tool can be figured out by matching the characteristic parameters' between the desired tool tip error trajectories and database trajectories.Then,the accurate linkage error value could be traced through similarity.The experiment is carried out to verify that this linkage error tracing method based on image recognition and trajectory similarity could be used to trace the linkage performance differences of five-axis machine tool accurately,and provide the guidance for the optimization of servo system parameters of five-axis machine tool.