Geometric Error Identification And Compensation Of Three-axis Machine Tool

Multi-axis CNC machine tools are widely used in aerospace,industrial robots,shipbuilding,vehicle engineering and other fields because of their high precision,strong adaptability,and efficient processing.They are called the " Industrial machine tool" of modern manufacturing.In order to obtain the distribution of linear axis geometric errors of three-axis CNC machine tools,this article focuses on three-axis CNC machine tool kinematic error modeling,three-axis CNC machine tool error identification algorithm,error detection and compensation,and three-axis CNC machine tool accuracy field construction.The main work of this paper is as follows:In terms of kinematic modeling of three-axis CNC machine tools,a double ballbar based error detection method is proposed for the current problems of high cost and low identification accuracy for detecting linear axes.First,from the angle of error definition,the influence of position independent geometric errors on the identification of position dependent geometric errors is eliminated,and 18 error models are selected.On this basis,based on product of exponentials and the three-axis CNC machine tool-double ballbar testing kinematic chain,a two-axis linkage comprehensive error model was constructed.The model can obtain all error elements by identifying the error-sensitive direction of the double ballbar,without identifying in the non-error-sensitive direction,and improving the accuracy and efficiency of identification.In terms of error identification of three-axis CNC machine tools,a mixed-order Chebyshev polynomial pre-fitting model is proposed to solve the problem that the integrated error model cannot be decoupled due to the position-related geometric error and geometric characteristics.At the same time,in order to improve the accuracy of the identification error elements,an installation error identification model is established,and the installation error is identified through the linear regression method.By combining the comprehensive error model,the pre-fitting model,and the simplified rod length model,the comprehensive error coefficient model is established,and 18 error elements are solved and identified through 5 pseudo-inverse algorithms.In terms of error detection and compensation,the experiment was carried out on the XK714 D three-axis CNC machine tool.The decoupling of the comprehensive error coefficient model was completed through the bi-orthogonal axis experiment,and 18 error elements were identified.The identification results were carried out according to the NC code compensation method.The compensation results show that the comprehensive errors of XY,XZ,YZ bi-orthogonal axis experiments are reduced by82.02%,91.63%,and 70.6% respectively after compensation,verifying the effectiveness of the geometric error identification method proposed in this paper.The residuals of the Chebyshev polynomial pre-fitting model before and after the improvement are compared,and the results show that the mixed-order Chebyshev polynomial pre-fitting model has higher accuracy.In terms of the accuracy field of three-axis CNC machine tools,the XK714 D threeaxis linkage comprehensive error model is constructed according to the product of exponentials,the three-axis CNC machine tool accuracy field is constructed based on experimental data,and the error distribution of the accuracy field is analyzed.