Locators’ Layout Optimization For Flexible Sheet Metal Workpiece Using The Genetic Algorithm

Automotive body which assembled by numerous automobile panels is an important part ofthe vehicle. The manufacturing quality of it affects directly the final quality, as wind noise,tightness, dynamic property, and appearance of the automotive. The errors occurred in theassembly process of automotive body come mainly from the manufacturing deviations ofautomobile panels and the positioning errors in the detection and welded assembly process. Themain contents in this paper were to optimize the location positions of the inspection fixture andwelding clamp fixture. With the optimized location plan, the errors caused by positioningcould be reduced and the manufacturing errors of automotive body could be remained at alower level correspondingly.Automotive panels have some characteristics, such as small relative thickness, hugeoverall dimension, flexible and so on. Because of these characteristics, the “3-2-1” locatingprinciple, traditionally used in the locating of rigid part, could not be enough to control thedeformation of automotive panels during locating process. With the improvement ofautomobile’s manufacture level, major breakthroughs have been made in the study ofautomotive panels’ locating design. In recent years, The “N-2-1” locating principle which isaccepted by most of the vehicle manufacturing enterprises and scholars is widely used in thelocator’s layout for the flexible sheet metal workpiece, where N, the number of locators onprimary datum, is the key to sheet metal fixture design. At present, locator’s layout is frequentlydecided by experience, and often leads to unsatisfactory locating precision in sheet stampingand assembly.In this paper, a genetic algorithm, which was programmed using APDL (ANSYSParametric Design Language), was proposed to lay out the N locators for the flexible sheetmetal workpiece. This method was successfully applied in the study of the locators’ layout offlat and curved surface workpiece, by analyzing the phenomenon of deviation amplification onobserving point in curved surface workpiece. A method of considering the deviation ofworkpiece was proposed to optimize locators’ layout, and the results shown it had a guidingsignificance to the optimization method of locators’ layout of flexible sheet workpiece.