DESIGN OF A PROCESS-CONTROL SCHEME FOR DEFECTS PER 100 UNITS BASED ON AOQL

A process control scheme is developed in which decisions as to the frequency of sampling are made based upon the choice of an Average Outgoing Quality Limit. The scheme utilizes plotted points on a U-control chart for defects and the theory of runs to determine when to switch among Reduced. Normal, Tightened, and 100 percent inspection. The scheme is formulated as a semi-Markov process to derive steady state equations for the probabilities of being in Reduce, Normal, Tightened, or 100 percent inspection and for Average Outgoing Quality and Average Fraction Inspected. The resulting system and the computer programs used to derive it are discussed.