Abstract: 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.

Key words: Maintenance planning, Multi-station assembly processes, Quality loss, Tolerance design, Variation propagation