A Method for Optimizing the Precision of a Five-Axis Machine Tool Based on Tolerance

The tolerance of critical components in five-axis machine tools directly impacts the overall machining accuracy of the entire system. This paper presents a tolerance optimization method for machine tools that is grounded in sensitivity theory and the NSGA-II algorithm. First, a mapping model is established to relate tolerance parameters to geometric and spatial motion errors. Second, a gradient-based sensitivity index, which has a clear physical interpretation and high computational efficiency, is defined to quantify the influence of individual tolerances on the spatial motion errors. Recognizing the limitations of existing tolerance allocation methods, this study introduces the innovative concept of tolerance control cost (the sum of the products of tolerance sensitivity and tolerance value for each parameter), and an optimization model is formulated to minimize this while ensuring the spatial motion error meets the requirement. The NSGA-II algorithm is employed to solve this model. Simulation results demonstrate that the tolerances of components can be significantly relaxed (thereby indirectly reducing manufacturing costs) while still ensuring the desired spatial motion error of the entire machine, validating the feasibility and effectiveness of the proposed method.