Joint Determination of the Imperfect Maintenance and Imperfect Production to Lot-sizing Problem

This paper deals with an integrated model for the joint determination of both economic production quantity (EPQ) and level of preventive maintenance (PM) for an imperfect production process. This process has a general deterioration distribution with increasing hazard rate. The effect of PM activities on the deterioration pattern of the process is modeled using the imperfect maintenance concept. In this concept, it is assumed that after performing PM, the aging of the system is reduced proportional to the PM level. After a period of time in production, the process may shift to out-ofcontrol states, either type I or type II. A minimal repair will remove type I out-of-control state. If type II out-of-control state occurs, the production process has to stop followed by the restoration work. Examples of Weibull shock models are given to illustrate that performing PM results in a lower cost than no PM action.