An Identification Method of Squareness Errors Based on Volumetric Error Model in Machine Tools

In the machine tool, geometric errors would largely influence the machining accuracy. The geometric errors include the Position Dependent Geometric Errors (PDGEs) and the Position Independent Geometric Errors (PIGEs), and the squareness errors are important PIGEs influencing the volumetric error largely. The measurement of the squareness errors are usually with low accuracy considering the overall error modeling and compensation. The other PDGEs such as the straightness errors and angle errors of corresponding axes are coupled with squareness errors or the Abbe errors are integrated in the measurement process of squareness errors, which is usually ignored in the overall error compensation. New method to obtain the accurate value of squareness errors to improve the volumetric accuracy is investigated considering the aspects. This paper proposes a new method to measure and identify the squareness errors of machine tools considering the volumetric accuracy based on the volumetric error model. The volumetric error model based on screw theory is proposed and then the identification method for the squareness errors is deduced in theory considering a 3-axis horizontal machine tool. Experiments with the measuring method and other traditional measuring methods have verified that the 3 identified squareness errors are in accordance with the measured squareness within the accuracy range. Moreover, the 6 face diagonal errors are calculated with the identified squareness errors and other squareness errors in different methods, which are compared with the measured face diagonal errors. It shows that compared with the traditional measurement of squareness errors, the proposed method shows more effective in the volumetric error evaluation process.