Inspection and correction policies in setting economic product tolerance

Traditionally, inspection for quality of a product is performed only at the final stage of the production process. This means that any non-conformance has been manufactured at the time they are inspected. Recently, incorporating the complete inspection into the production process becomes available due to manufacturing automation and smaller production lot size. These also permit, for certain products, necessary correction or rework in order to meet product specifications or requirements. For being competitive, additional expenses come from inspection as well as correction should be minimized. In this paper, we consider an approach called product loss function, together with costs of inspection and correction, to develop an expected cost model. Optimization is done based on trading off the components of the model to select the most profitable tolerance. This optimization procedure not only leads to an optimum product tolerance, but also reflects the balance between manufacturer expenses to improve the quality of product and the loss suffered by a customer. Similarly, a different policy is applied and seeks the effect on tolerance. The effect of imperfect measurement on product tolerance will also be presented.