COMBINING THE TAGUCHI'S QUALITY LOSS FUNCTION AND DIFFERENT COST-TOLERANCE FUNCTIONS FOR ASSEMBLY TOLERANCE OPTIMIZATION

摘要

In the engineering practice, tolerance is defined as the maximum deviation from a nominal specification within which the component is still acceptable for its intended purpose. For practical considerations, tight tolerances increase the cost of production, while larger tolerances are less costly, but they are usually associated with poor performance. In a mechanical assembly, the allocation of tolerances among the components can significantly affect the resulting manufacturing costs. Designers often assign tolerances arbitrarily or base their decisions on insufficient data or deficient models, which result in many problems at the stage of manufacturing. In recent years, much research has been done to find the least cost-tolerance allocation by employing cost versus tolerance functions. In order to evaluate the total cost of an assembly accurately, combining the Taguchi's quality loss function with the cost-tolerance function is necessary. For most of the tolerance allocation researches, the same cost-tolerance function for each component in an assembly was assumed. However, in a manufacturing assembly, each component may have different cost-tolerance functions associated with it. To determine the optimal tolerances for individual components becomes more challenging. The purpose of this research is to combine different cost-tolerance functions with quality loss functions to determine the optimal tolerances for individual components so that the total assembly cost is minimized subject to a specified constraint.