A novel assembly tolerance analysis method considering form errors and partial parallel connections

As one of key enabling technologies in digital twin-based assembly precision analysis, three dimensional (3D) assembly tolerance analysis technology has increasingly become an important means for predicting the assembly accuracy and verifying the assembly quality of mechanical assemblies. However, current methods exist some deficiencies that (i) the traditional model mostly cannot cover geometric tolerances or form errors in 3D assembly tolerance analysis, and (ii) a loss of assembly accuracy can be caused by ignoring these parallel connections in the assembly deviation propagation. To address these issues, this study proposes a novel assembly tolerance analysis method considering form errors and partial parallel connections with assembly accuracy and reliability guarantees in mechanical assemblies. First of all, through the integration of the unified Jacobian-Torsor model and skin model shapes, the resulting integrated Jacobian-skin model shapes model is presented, which contains the two advantages of easy-to-use tolerance propagation and geometric tolerance representation. Secondly, a novel improved approach combined with progressive contact method and algebraic operation is introduced into the assembly deviation propagation, which can realize the calculation of assembly relative positioning errors in both serial and partial parallel connections. Meanwhile, an overall calculation scheme of the proposed method is elaborated for assembly tolerance analysis with a statistical way, which is used to obtain the final deviation results of the assembly functional requirements (AFRs). At last, a typical mechanical assembly involving three parts is used as a case study to illustrate the effectiveness and feasibility of this solution.