多工位装配过程夹具系统公差和维护综合优化设计

提出一种面向二维多工位装配过程、综合考虑装配夹具系统全寿命周期成本、产品零件孔制造成本和产品质量损失成本的公差和维护综合优化方法。分析多工位装配尺寸偏差传递关系，建立多工位装配过程产品质量损失模型。然后根据4-2-1夹具定位原则，构建考虑夹具磨损过程损失的夹具定位销副偏差统计数字特征模型。继而发展了以夹具系统全寿命周期成本、零件孔制造成本和和产品质量损失成本为装配总成本最小化的定位销公差、零件孔公差与更换周期优化模型。以汽车侧围装配过程为例，分别研究定位销公差、零件孔公差、定位销更换周期、配合间隙、平均磨损率和磨损率方差对装配总成本的影响，并优化设计定位销公差、零件孔公差和定位销更换周期。所提出的综合优化设计方法比采用定位销等公差设计、零件孔等公差设计、定位销与零件孔等公差设计和定周期更换设计的装配总成本分别减少了16.25%、11.31%、39.93%和13.54%。该方法为产品装配夹具系统高质量低成本设计提供了一种新的途径。

Integrated Optimized Design of Tolerance and Maintenance Planning for Fixture System in Multi-station Assembly Processes

Based on the assembly total cost including the fixture system life-cycle cost, the part hole fabrication cost and the product quality loss cost, the optimization method of integrated tolerancing and maintenance planning for two-dimensional multi-station assembly processes is developed. The relationship of dimensional variation propagation for two-dimensional multi-station assembly processes is analyzed, and the quality loss model of multi-station assembly processes is built. According to the fixture locating principle of 4-2-1, the deviation statistics feature model of the pin-hole locating pair is presented. Then the optimization model of integrated tolerancing and maintenance planning is proposed, in which the assembly total cost is minimized including the fixture system life-cycle cost, the part hole fabrication cost and the product quality loss cost. Automotive body side aperture assembly is given as an example to study the influences of the locating pin tolerance, the part hole tolerance, the pin replacement cycle, the fit clearance, the mean wear-out rate and wear-out variance on the assembly total cost. Furthermore, the locating pin tolerance, the part hole tolerance and the replacement cycle are optimized and designed. Compared with other separated designs such as uniform tolerance of locating pin, uniform tolerance of part hole, uniform tolerance of locating pin and part hole, and fixed replacement cycle separately, the assembly total cost of the integrated design method descreaes by 16.25%, 11.31%, 39.93% and 13.54% respectively. It provides a new way of designing high-quality and low-cost fixture system for product assembly.