Economic production quantity model for randomly failing production process with minimal repair and imperfect maintenance

This study applies periodic preventive maintenance (PM) to economic production quantity (EPQ) model for a randomly failing production process having a deteriorating production system with increasing hazard rate: minimal repaired and reworked upon failure (out of control state). The minimal repair performs restorations and returns the system to an operating state (in-control state). It is assumed that, after each PM, two types of PM are performed, namely imperfect PM and perfect PM. The probability that PM is perfect depends on the number of imperfect maintenance operations performed since the last renewal cycle. Mathematical formulas for the expected total cost are obtained. For the EPQ model, the optimum run time, required to minimize the total cost, is discussed. Various special cases are considered, including the maintenance learning effect. Finally, a numerical example is presented to illustrate the effect of PM and setup, breakdown and holding cost.