Abstract: The machining accuracy of computer numerically controlled (CNC) machine tools is an important factor affecting product quality. To improve the machining accuracy reliability of multi-axis CNC machine tools, based on the product-of-exponential (POE) theory, the geometric error model and machining accuracy reliability model of machine tools are established. Using the improved first-order second-moment method, the machining accuracy reliability of machine tools is analyzed, as well as the sensitivity of geometric error terms. A universal accuracy allocation method to optimize the machining accuracy of machine tools is proposed, which not only gives the physical meaning of machine tools’ perpendicularity error but also solves the problem of matrix singularity. Taking a large guideway gantry grinder as an example, according to the sensitivity analysis results of geometric error terms, the machining accuracy reliability of the grinder was improved by optimizing and adjusting the parameters of main geometric error terms. The results show that the accuracy allocation method proposed in this paper is both effective and practical.

Key words: accuracy allocation, improved first-order second-moment method, machining accuracy reliability, product-of-exponential model