Research On Dynamic Accuracy Detection Method Of Five-axis CNC Machine Tools Based On The S-shaped Test Piece

The S-shaped test piece is the first international testing standard proposed by Chinese machine tool industry,which is used to assess the comprehensive machining performance of five-axis CNC machine tools,especially to make up for the shortcomings for traditional test piece in the dynamic accuracy detection of five-axis CNC machine tools.However,at present,there are few studies on the detection mechanism,method and index for dynamic accuracy of five-axis CNC machine tool based on the S-shaped test piece.In order to popularize the application of S-shaped test piece in the dynamic accuracy detection of five-axis CNC machine tool,the research on the dynamic accuracy detection method for the five-axis CNC machine tool based on the S-shaped test piece is systematically conducted from the following aspects:(1)Based on the simplified dynamic error transfer function for the electromechanical coupling model of the five-axis CNC machine tool,delay continuous method(DCM)is proposed,which makes the dynamic error of servo feed system can be quantitatively expressed by mathematical formula.At the same time,linear combinatorial value(LCV)index and combinatorial LCV(CLCV)index are proposed based on the DCM to directly evaluate the effectiveness of dynamic accuracy test piece.The proposed two indicators can not only be used to evaluate the requirements of dynamic accuracy test piece on the linkage performance of five-axis CNC machine tools,but also can be used to assess the needs of any part on the dynamic performance of fiveaxis CNC machine tools before machining.Moreover,the existing test pieces can be optimized and better new dynamic accuracy test pieces can be proposed based on the LCV index and the CLCV index,which has important theoretical significance and practical application value.(2)A novel approach to calculating the dynamic error distribution reflected on dynamic accuracy test pieces is proposed,which makes the dynamic error distribution reflected on dynamic accuracy test pieces can be expressed quantitatively.The superiority of the S-shaped test piece in dynamic error detection of servo feed system for five-axis CNC machine tool compared with other test pieces can be proved theoretically.(3)The effect of multi-axes synchronous dynamic error of five-axis CNC machine tool on tool pose error is analyzed.Then,the mapping model between tool pose error and dynamic error reflected on test pieces is established.Based on this model and the analysis results on NC machining instruction characteristics of S-shaped test piece,11 sets of experiments were designed to simulate the dynamic error distribution reflected on machined S-shaped test piece in the case of mismatched linkage performance.The above experiments are used to quantitatively study the effect of linkage performance between different axes on the surface dynamic error distribution of S-shaped specimens,which provides a theoretical basis for the dynamic error tracing of five-axis CNC machine tool based on S-shaped test piece.(4)A set of statistically significant sensitivity indices for the surface dynamic error of S-shaped test piece are established to analyze the relative importance of dynamic error terms with inter axial linkage.The contribution of the tool pose error caused by the dynamic error source of inter axial linkage to the surface dynamic error of the machined S-shaped test piece is quantified,then,the dynamic error term of the key inter axial linkage is accurately evaluated.Based on the sensitivity index,a dynamic error tracing method for five-axis CNC machine tools is proposed,which provides important theoretical guidance for precision design and dynamic error identification of five-axis CNC machine tools,and has practical engineering application value.