Five-axis Machine Tool Rotation Axis Geometric Error Measurement And Identification Research

With the continuous development and progress of the manufacturing industry,especially the rapid development of the aerospace field,five-axis machine tools are widely used in the processing and manufacturing of complex curved surfaces such as aero-engine parts.There are two rotating axes in five-axis machine tools,and the error elements are many and affect each other.In order to improve the machining accuracy of five-axis machine tools,aiming at the geometric error modeling of five-axis CNC machine tools,the geometric error measurement and identification method of the rotating axis of the machine tool and the error compensation technology are studied.The specific research contents are as follows:(1)The geometric error of the five-axis machine tool is studied,the geometric error model of the five-axis machine tool is established based on the screw theory,and the error screw is introduced in the modeling process to model the geometric errors of the machine tool.The geometric error model of the machine tool based on the helical theory is consistent with the results based on the multi-body system theory,and there is no need to establish a local coordinate system in the modeling process,and the tool and workpiece only need to refer to the machine tool coordinate system.(2)The radial,tangential and axial error measurement modes of the BC rotation axis based on the ballbar are adopted.The mathematical model of error in this mode is established,and the analytical solutions of 8 position-independent geometric errors(PIGEs)and 12 position-dependent geometric errors(PDGEs)of the two rotating axes are obtained through identification.All the geometric errors of the two rotating axes can be obtained at the same time,which lays the foundation for the subsequent error compensation.Combined with the previously established machine tool error model,the effects of eight PIGEs on the ballbar measurement trajectory were simulated and analyzed.(3)Based on the differential transformation theory,the influence of the displacement of the motion axis on the tool space change is studied,and the relationship between the two is established.The geometric error compensation model is established,and the motion amount of each motion axis after compensation is obtained by the least square method.Comparing with the method of compensating the direction vector first and then compensating the position vector,it is proved that the proposed compensation method can compensate efficiently.(4)Taking the Mikron MILL E 500 U five-axis machine tool as the research object,the radial,tangential and axial measurement experiments were carried out on the BC rotary axis with the help of the ballbar,and 8 PIGEs and 12 PDGEs of the BC rotary axis of the machine tool were obtained through geometric error identification.After the error compensation,both the position error and the angle error are greatly reduced,which fully demonstrates the accuracy and effectiveness of the established geometric error model,the proposed measurement mode and the corresponding error compensation method.