Tolerance Allocation of Sheet Metal Assembly Using a Finite Element Model

A tolerance allocation scheme for automotive body assembly must consider both product tolerance requirements and manufacturing capabilities. The design/functional requirements are considered to be the dimensional requirements of the product, and the manufacturing capabilities are considered to be the tolerance allocated. However, customer demand for quality requires tight tolerance, which current sheet metal manufacturing cannot deliver. Thus, a high product cost is incurred to satisfy customers' high requirements in relation to sheet metal products. In this paper, a generic finite element tolerancing methodology is developed for sheet metal assembly. This methodology is capable of determining the maximum allowable manufacturing tolerance for components before assembly, which satisfies the product requirement as a whole. This method enables a tolerancing scheme to be used in state of the art automotive body panel design.