Inspection strategies for multistage production systems with time-varying quality

An economic, cost of quality model is formulated for a production system with multiple inspection locations and sampling. The model is applied to a thermal printer for digital photographs to determine when inspection of incoming material is appropriate. A simple dynamic model of quality is used, allowing for common-cause defects and the evaluation of sampling plans. The opportunity to correct quality problems more quickly when they are detected earlier is also considered. The cost structure used allows the costs of quality improvement, and not just that of defective units, to be considered.