Optimal Tolerance and Clearance Allocation in Mechanisms to Minimize Manufacturing Cost

Abstract

Abstract A procedure has been developed for the optimal allocation of tolerances and clearances in complex assemblies. The objective is to minimize manufacturing costs and sensitivity to variations in the design variables. The assemblies considered are single loop planar and spatial mechanisms including those with analytically defined surface contact joints. The procedure, to be used in early design stages, allows the incorporation of manufacturing tolerances and clearances based on actual manufacturing process and cost information. This allows the designer’s intent and the manufacturing and process capabilities to be tied together in the development of the product or assembly. The allocation of tolerances is done with the idea of minimizing the overall “life cycle cost” of the assembly, which not only involves the actual manufacturing cost but also the cost involved in maintaining the design variables within tolerable values. A multicriteria optimization procedure is used to handle the two aforementioned conflicting objectives. The kinematic analysis of mechanisms with clearance joints is performed using an iterative procedure along with an equivalent “clearance link” model.