Research on the tolerance allocation of machine tools based on adaptive genetic algorithm

The current modeling methods of machine tool's geometric precision often ignore the effects of adjustment, lacking of scientific and feasible approaches to allocate the tolerance of machine tools. This paper adopts the state space model to describe the actual assemble process of a machine tool, and the adjustments in the assemble process are considered. Thus a more accurate model is set up. By introducing the index of the species diversity, an adaptive genetic algorithm for tolerance allocation is built up. The method was applied in the tolerance distribution of the angular tolerance in TGK46100. Firstly, the relationship of assembly accuracy requirements and angle error of large parts is constructed. Then taking the total cost of parts machining as the objective function and using the adaptive genetic algorithm, the optimal angle tolerance is obtained. The results show that, compared with the deviation accumulation method without considering the assembly adjustment, the machining accuracy of parts is relaxed and the maximum relaxation rate reaches 12%, with an average of 36.4%. Hence the parts manufacturing cost is reduced when the final assembly accuracy requirements are met. This research provides an accurate modeling method for machine tools' tolerance distribution.