Early prediction method for assembly precision of mechanical system and assessment of precision reliability

Assembly precision is an important index, because it can ensure the quality of mechanical products and the final basis, and determine the overall performance of the products. In the early design stage, the prediction of assembly precision of schemes is significant. Therefore, considering part processing error, we proposed a prediction method for assembly precision of mechanical transmission system. Based on meta-action theory and small displacement torsor (SDT) model, common geometric elements were analyzed under multi-tolerance coupling and the error transfer of joint-surface for meta-action unit. Thus, we established the error model of joint-surface and qualitatively determined the potential error’s accumulative transmission paths of transmission system. We also quantitatively built the assembly precision prediction model of transmission system combining with the Jacobian-Torsor method, and calculated the precision reliability value. Finally, the effectiveness was verified by an example of NC machine tool’s transmission system. The method provides a way of thinking about solving the precision prediction and reliability evaluation of mechanical transmission systems in the early design stage and a basis for the final assembly precision prediction, simulation and testing of mechanical products.