Abstract: The automobile body is made of sheet metal stamping parts which are welded and assembled hierarchically. The sheet metal of the automobile body has a great flexibility. The deformation caused by external load will directly affect the transmission and accumulation of assembly deviation and finally affect the assembly accuracy and function. This paper focuses on the problem of inconsistency in the window lifting process, and a 3D assembly tolerance analysis model including finite element deformation is established to reveal the influence of sealing resistance and the rigidity of the inner panel of the door on the assembly state of the lifter. Based on the benefit ratio of tolerance optimization as the evaluation indicator to determine the optimization plan, an optimized tolerance design and an improved lifting consistency are realized. The results show that when the surface profile of the matching surface of guide rail and bracket is tightened to 0.5mm and the position of the mounting hole of glass and bracket is tightened to 0.9mm, the assembly tolerance of the door model conforms to the set goal and meets the requirements of lifting smoothness.

Key words: flexible assembly, 3D tolerance optimization, glass lifter, finite element simulation