Optimal allocation of process tolerances and stock removals

Tolerance charts have been used as an effective tool to ensure that a specific processing sequence is appropriate for a product of the required dimensions. Different arrangements of manufacturing tolerances and amount of stocks to be removed at each machining operation result in different production costs. Instead of existing heuristic, experience-based methods, this paper presents a new approach by means of which process tolerances and stock removals are simultaneously allocated through an optimization program. In approaching the optimal design, a cost function, the value of which varies with design variables (process tolerance and stock removal at individual cuts), is chosen as the objective to be minimized. During the searching process, the variables are subject to the constraints derived from dimension chains associated with a tolerance chart.