Error Compensation And Accuracy Reliability Evaluation Of Five-axis CNC Machine Tools

CNC machine tools represent the technical level of precision manufacturing,and its accuracy and reliability are important indicators to measure the quality and safety performance of machined parts.It is of great significance for the development of CNC machine tools and the improvement of national manufacturing level to improve the machining accuracy and ensure the reliability of machine tools.The error variation law is analyzed and modeled,and the computer calculation,prediction and control are used to make a compensation for the opposite error in the process of machining,which can greatly improve the machining accuracy of the machine tool.This paper introduces the related process and technology of error compensation in detail,analyzes the influence of the position of the rotating axis on the comprehensive error of the machine tool,establishes the mathematical model,and evaluates the accuracy reliability of the machine tool by using the reliability theory.The main achievements are as follows:(1)The paper introduces the error compensation technology and analyzes the significant advantages of error compensation in improving the accuracy of machine tools.It shows the scientific and engineering nature of error compensation from the aspects of error and error source,error element modeling technology,error detection and optimization of temperature measurement point selection,establishment of machine tool motion model and comprehensive error,implementation scheme and effect test of error compensation control system.(2)Based on the theory of multi-body system,the comprehensive error model of five-axis CNC machine tool is established.Firstly,by using homogeneous coordinate transformation,the static and motion state of machine tool are analyzed and the static and motion characteristics matrices of machine tool are obtained.Secondly,considering the generation of error sources and the influence on the movement process of machine tools,the static and motion error matrices are established.Finally,the comprehensive error model of machine tool is obtained by the spatial coordinate relationship between the cutting point and the workpiece forming point in ideal condition and actual state.(3)Based on the orthogonal polynomial regression method,a polynomial model which can be used for error compensation is established.Orthogonal polynomials are used for statistical analysis of machine tool comprehensive error data,significant regression terms are retained,regression coefficients are calculated and regression functions are obtained.The comparison shows that the regression model has a good fit degree for the original data points,the fitting residual is greatly reduced and the fluctuation is lower than the original error,which has a good effect in error modeling compensation.(4)Based on the reliability theory and reliability method,the reliability of machine tool accuracy is analyzed.The random error variables in the machine tool precision function are iterated by the checking point method,and the reliability index within the allowable error is obtained,which shows that the machine tool precision has high reliability.After sampling and analyzing the error variables by Monte Carlo method,the conclusion of the checking point method is verified again.