Geometric accuracy enhancement of five-axis machine tool based on error analysis

Abstract

The characteristics of geometric error affect both the positions and orientations of a five-axis machine tool, which are very important for precision manufacturing. It is necessary to conduct quantitative analysis for the above characteristics to improve the precision of the five-axis machine tool. In this paper, the synthetic volumetric error model of the five-axis machine tool with a turntable-tilting head has been established, which describes the effect of 43 geometric error terms on position and orientation error vector intuitively. The multidimensional output of geometric error vectors in the workspace of the machine tool is sufficiently taken into account, and global quantitative sensitivity analysis is introduced to determine the effect of each geometric error on the precision of the machine tool. The results showed that geometric errors of the rotary axes are dominant sensitivity factors, reaching 59.32 and 51.59% of sensitivity indices of the position and orientation error vector, respectively. Furthermore, geometric error terms that are noncritical and critical are extracted according to the result of mutual information analysis. Those geometric errors were removed from the geometric error compensation model, which are at the same time insensitivity errors and nonsignificant geometric errors. The geometric error compensation results show that the accuracy of the machined parts with complex curved surfaces was improved 56.22% after error compensation based on sensitivity and mutual information analysis. This research provides a feasible methodology for analyzing the effect of geometric errors and determining the compensation values of the machine tool.