Single-station Assembly Variation Analysis Based On Sheet Metal Parts Of Automobile Body

As one of the four component parts of vehicle，the quality of auto-body directlyinfluences the appearance, quality and performance of automobile. Auto-body is assembledby compliant sheet metal parts. The assembly variation of each assembly part throughpropagation will have an effect on the quality of the final product. In the traditional modelof assembly variation analysis, there are two reasons that lead to an inaccurate result ofassembly variation. One is that most scholars mainly adopted the point contact to analyzethe welding of assembly parts rather than surface contact which is a more accurate method,another reason is that localization deformation caused by the fixture positioning is alwaysneglected.Therefore, as the basis of total body assembly variation analysis, the accuracy andefficiency of single-station assembly variation analysis has important significance for thecontrol of assembly variation of vehicle. To solve the above problems, with processinganalysis of assembling auto-body compliant sheet metal, this paper studies the weldingsmall plane contact model, reveals the transfer and accumulation mechanism of variationand builds the flexible assembly variation analysis model based on power balance method.Based on the “N-2-1” locating principle, this work proposes a method to optimize thewelding point of assembling the compliant sheet metal. Considering the deformation of thekey point of the part by multi-position force, this work generates the optimal locating pointby genetic algorithm on the primary plane, which can minimize the effect coefficient whenit is suffered from multi-position force on positioning point.Finally, a fixture is designed and manufactured. The fixture adopted the variablepositioning strategy which is applied to analyze compliant sheet metal. The fixture, whichmakes three-dimensional anchor point adjustable, uses the T slot of adjustable positioningand establishes multiple anchor point, which can realize the positioning strategy changing from “3-2-1”to“N-2-1”. The assembly variation model is successfully applied to theassembly variation analysis of auto-body’s taillights, which verifies that the model iscorrect. It makes the control of assembly deviation of components more effective whichcan improve the accuracy and efficiency of simplex post assembly variation analysis. Theresult of this paper has significance for single-station assembly variation analysis ofcompliant sheet metal.