Influences of linear and angular compensation on volumetric accuracy of precision machine tools

Abstract

Geometric errors of machine tools are one of the main contributors for machining inaccuracies. A multi-step error measurement and compensation method is proposed in this paper to investigate the effects of different geometric errors on volumetric errors. The kinematic error chain is built using multi-body system theory (MBS) and homogenous transformation matrices first. Then, the original geometric errors without any compensations are measured and the deviations of tool tip caused by different geometric errors are calculated. Furthermore, various compensation strategies considering diverse geometric errors effects are carried out in the machine tool to validate the predicted volumetric errors. The multi axis calibrator, which can detect six errors of a translational axis in one measurement, is used to measure the variations of 18 errors of translational axes and volumetric diagonal errors of a three axes machine tool. Besides, the squareness errors were measured by a ball-bar. The pragmatic effects of positioning, straightness, angular and squareness errors on volumetric errors are derived from comparisons between various compensation results. Results reveal that linear errors effect the whole volumetric positioning errors while the angular errors mainly effect the volumetric positioning errors of the region far from reference coordinate point.