Early prediction method for assembly precision of mechanical system and assessment of precision reliability
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ORIGINAL ARTICLE
Early prediction method for assembly precision of mechanical system and assessment of precision reliability Xin Yang 1 & Yan Ran 2 & Zhichao Wang 1 & Zongyi Mu 1 & Genbao Zhang 2 Received: 9 July 2020 / Accepted: 4 November 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract 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. Keywords Assembly precision . Error analysis . Prediction method . Precision reliability
1 Introduction Assembly errors are formed by the cumulative transfer of multiple local error sources based on the topological structure of mechanical products [1–3]. However, the structure of mechanical products is often complex and changeable. Complex mechanical products often contain thousands of parts. The geometric elements and matching forms among parts are also various [4, 5]. Therefore, setting up a general assembly error analysis model has become an urgent problem to be resolved in the manufacturing industry. In this paper, the tolerance modeling is carried out for the machining errors of transmission system’s parts firstly. Accurately describing the geometric elements is the key of tolerance modeling according to the tolerance value [6, 7]. Whitney [8] established the assembly * Yan Ran [email protected] 1
College of Mechanical Engineering, Chongqing University, Chongqing 400044, China
2
State Key Laboratory of Mechanical Transmissions, Chongqing University, Chongqing 400044, China
error transfer model, who applied the homogeneous transformation matrix used for posture operation in robotics for assembly tolerance analysis. Zhou et al. [9, 10] set up the error transfer model and quality evaluation method based on the assembly sequence, solved the accumulated errors of assembly according to the error transfer
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