Simultaneous Determination of Production Cycle and Inspection Schedules in a Production System

Classical Economic Manufacturing Quantity (EMQ) models have usually ignored the possibility of process deterioration and the existence of defective items in the production lot. Moreover, the use of machine inspection for maintenance and restoration purposes has not been considered. On the other hand, past studies on maintenance models do not consider the length of a production run to be a decision variable. This paper addresses the problem of joint control of production cycles or manufacturing quantities and maintenance by inspection. A simple relationship has been developed to determine the effectiveness of maintenance by inspection. Furthermore, when maintenance by inspection is adopted, it is shown that the optimal inspection intervals are equally-spaced. The problem of simultaneous determination of EMQ and the inspection schedules is solved by using an approximation to the cost function. The resulting EMQ is found to be an adjustment to the classical EMQ. Finally, the relationships between different parameter values and the magnitudes of the cost penalty for using the classical EMQ are examined.