Comprehensive Analysis and Evaluation of the Geometric Errors of the Rotating Axis of Five-Axis Double-Pendulum Machine Tools Based on S-shaped Samples

The geometric error of the rotation axis of a multi-axis machine tool is highly sensitive among the geometric errors of the machine tool. Therefore, establishing an evaluation system for geometric errors of rotation axes is important for improving the machining accuracy of workpieces. First, a model for predicting the geometric error of the rotation axis was established based on the multi-body system theory, and then the mapping relationship between the geometric error of the rotation axis and each region with curvature changes in the S-shaped sample was identified. Next, based on the average value in seven different regions with curvature changes in the S-shaped sample, the weights of the mapping regions were calculated. Subsequently, the weights of the 12 geometric errors of the rotation axis ( epsilon(x)(A), epsilon(y) (A), epsilon(z) (A), delta(x)(A), delta(y)(A), delta(z) (A), epsilon(x) (C), epsilon(y)(C), epsilon(z) (C), delta(x)(C), delta(y) (C), and delta(z)(C)), and the weights of two rotation axes were identified to establish a comprehensive evaluation system for the geometric errors of rotation axes. Finally, an S-shaped specimen was machined and subjected to on-machine measurement experiments on a five-axis CNC machine, and two rotary axes were evaluated using the established evaluation system. The results show that the maximum average difference between the actual and theoretical values for the S-shaped samples is within reasonable limits. Further, the comprehensive performance of the machine's rotation axes was evaluated step by step based on the theoretically calculated weight values.