Abstract: According to the topology of large CNC gantry guideway grinder, a geometric error propagation model including 21 parameters is established by the theory of multi-body system and coordinate transformation method, and the model is verified by tests that it has ideal prediction accuracy. Limit state function of the reliability of machining accuracy to meet grinders design requirements is built on the geometric error propagation model. Reliability approximately model is established by response surface method with error samples from 25 sets of position of the grinder working stroke and the reliability of the machining accuracy of each group working position is analyzed. With the mean and minimum of 25 items of reliability as the index for judging the machining accuracy performance of grinders, the sensitivity analysis is obtained for the minimum reliability corresponding to the grinder working locations. The importance degrees of the factors that affect machining accuracy are sorted by sensitivity. According to the results of the analysis, the distribution of error variables is optimized gradually by following the principle of accuracy proportionality until the mean and minimum of the reliability meet the design requirements. The optimization in precision distribution for large CNC gantry guideway grinder is verified feasible through numerical examples.

Key words: Error propagation model, Limit state function, Optimization in precision distribution, Response surface method, Sensitivity analysis