Identification of geometric errors of rotary axes on 5-axis machine tools by on-machine measurement

Geometric error is among the most important fundamental elements that significantly affect the machining accuracy of multi-axis machine tools. This paper developed an efficient, accurate, and automatic geometric error measurement and identification method for rotary axis of a five-axis machine tool based on on-machine measurement by using a touch-trigger probe with a test piece. Before on-machine measurement, the test piece is installed and pre-machined to a designated geometry. Then, the coordinates of the reference points on the test piece are indirectly measured at different rotary axis positions. The geometric errors of each rotary axis then can be identified individually and the calculation algorithm is easy to establish and solve. Due to the special features of this method, neither the geometric inaccuracy of the test piece nor its installation error on the workbench affects the geometric error measurement and identification results. Geometric errors of a five-axis machine tool with double table rotary axes are measured as an example to validate the efficiency and effectiveness.