Quality loss function based manufacturing process setting models for unbalanced tolerance design

In many manufacturing processes, unbalanced tolerance design is a common occurrence where the deviation of a quality characteristic in one direction is more harmful than in the opposite direction. Traditionally, the manufacturer of a component would set the process mean at a target value, but this method fails to minimise the expected quality loss. In order to minimise the expected loss of quality, the process mean should be shifted a little from the target value. Two specific models of quality loss functions are discussed; when the standard deviation of the quality characteristic remains constant, and when the standard deviation of the qualify characteristic is proportional to the process mean.