Research On Identification And Compensation Method Of Sphericity Error And Squareness Error Of Five-axis CNC Machine Tool

At present,Computer Numerical Control(CNC)machine tools mostly adopt the form of multi-axis linkage for parts processing,the processing efficiency has been further improved,and they are mostly used in the processing of precision parts in aerospace,automotive and other fields.However,the simultaneous machining of CNC machine tools with multi-axis linkage makes the error of the machine tool to be coupled,which will undoubtedly affect the accuracy of the processed parts and cannot meet the requirements of use.Therefore,this article aims to propose a rapid detection method for measuring and identifying the error of the translational axis of a multi-axis CNC machine tool during three-axis linkage and to improve the machining accuracy of the CNC machine tools through error compensation.In this paper,the machine tool error modeling,translational axes error identification experiment and geometric error compensation are studied respectively.The main contents of this article are as follows:In the process of establishing the comprehensive error model of CNC machine tools,the theory product of exponential formula is adopted,which is different from the traditional homogeneous transformation matrix method.There is no need to establish a local coordinate system,in the global system contains three translational axes squareness errors of the machine tool.The integrated machine tool error model simplifies the process of error model establishment and calculation.This paper presents a rapid method for measuring the squareness errors of the translational axes of CNC machine tools based on the spherical S-shaped paths of the Double Ball-bar(DBB).Different from the existing detection method in which the squareness error is measured multiple times in the plane with the linkage of two translational axes,the proposed error detection method adopts the linkage of the three translational axes of the machine tool and requires only one installation,avoid the influence of installation errors in multiple installation measurements,to make the error detection data collection more accurate and comprehensive.Only one experiment can identify the three squareness errors of the translational axes of the machine tool.Combined with the experimental data,the error is calculated based on the pseudoinverse matrix method,and the measurement result is verified by NC compensation using a spherical spiral path different from the error measurement.The error compensation path is installed and positioned in the same way as the error measurement path,without repeated installation.The compensation experiment adopts the method of comparative experiment verification.The machine NC code before and after error compensation is tested separately,and the experimental data collected in the two experiments are compared to verify the effectiveness of the detection method.Since the detection and compensation paths of the proposed DBB are both spatially irregular spherical paths,the coordinate transformation method and the method of equal division of the experimental path are respectively proposed,which solves the problem that the distance between the two bases is not constant and the movement speed is not synchronized with the machine tool.The accuracy of the experimental data and error detection experiment is improved.The influence of the sphericity error of machine tools on the machining accuracy is studied.The evaluation method based on the minimum zone sphere is proposed to solve the sphericity error of the machine tool.Because the experimental measurement path is carried out in the sphere,after studying the influence of the squareness errors on the machining accuracy of the machine tool,the influence of the sphericity error of the machine tool on the machining accuracy of the machine tool is explored.In this paper,the location and radius of the center of the least square sphere are determined based on the least square method,and the sphericity error is given.The existing evaluation methods mostly use the least square method to calculate the sphericity error,but because the least square method only estimates the position of the center of the sphere,the result of the error calculation is inaccurate,so this paper takes the position of the center of the least square sphere as the basis uses the minimum zone sphere method to further search and determine the sphere center position,find a more accurate sphere center position that meets the requirements,and use the new sphere center position as the basis for error calculation,which further improves the sphericity error calculation result.