Synchronous Measurement and Verification of Position-Independent Geometric Errors and Position-Dependent Geometric Errors in C-Axis on Mill-Turn Machine Tools

Abstract This paper proposes a synchronous measurement system of four position-independent geometric errors (PIGEs) and two position-dependent geometric errors (PDGEs) for the rotary axis in five-axis machine tools. The measuring instruments used in this system are a touch-trigger probe and two standard calibration spheres. The contribution of this paper is the simultaneous measurement of four PIGEs and two PDGEs (axial and angular positioning errors) can be directly analyzed through only one measuring process. It is expected to improve the shortcomings of previous studies that separately measured PIGEs and PDGEs. This paper analyzed the geometric errors of C-axis of a mill-turn machine tool MT-540. The process of calculation includes the establishment of the mathematical model of the machine and geometric error equations. Using the least squares method to solve the linear overdetermined system and calculate the values of the geometric errors. Before solving the geometric errors, the accuracy of the calculated process is ensured by using the simulated method. The simulation results also confirm the feasibility of this measurement system. Then using the data obtained from the experiment to calculate the geometric errors in the machine tool. During the experiment, the calibration procedure of the touch-trigger probe will be calibrated. After the calibration is completed, the mechanical coordinate values of the two standard calibration balls can be measured. The geometric error equations are programmed on the computer side, and the calibration spheres data obtained from the experimental measurement is substituted into the program to calculate the four PIGEs and two PDGEs.