مدل سازی بازرسی و تولید بهینه با حداقل تعمیر و ملاحظات دوباره کاری

This paper extends an integrated model of economic production quantity (EPQ) and preventive maintenance (PM) to incorporate possibilities of minimal repair and rework. Our model determines simultaneously the optimal number of inspections, the inspection interval, the EPQ, and the PM level. Numerical examples of Weibull shock models are given to show that allowing minimal repair and rework will raise the expected profit. Our analyses demonstrate that both minimal repair and rework significantly influence the optimal policy.

The classical economic production quantity (EPQ) model assumes that the production system is free of failures and that all items produced are perfect [1]. Many research efforts have been made to extend the classical EPQ model by loosening various assumptions. In a real world situation, the production process begins by producing lots in an in-control state, and it may become out-of-control by producing defective items. Rosenblatt and Lee [2] considered the effects of process deterioration on the optimal EPQ. They presumed that the time at which the process shifts from the in-control state to the out-of-control state follows an exponential distribution; they also found that the resulting EPQ is smaller than that of the classical model because the use of smaller lots produces fewer defective items. Porteus [3] obtained similar results. Hariga and Ben-Daya [4] extended the model to consider the case in which the deterioration of the process follows a general distribution. Salameh and Jaber [5] presented a modified inventory model which accounted for imperfect quality items when using the EPQ/EOQ formulae. Freimer et al. [6] developed the results that characterize the optimal run length and expected total cost with consideration of reducing setup costs and improving process quality. Jaber [7] also provided a mathematical model with numerical examples to investigate the lot-sizing problem for reduction in setups while considering reworks and interruptions to restore process quality.

The main contribution of this paper is in the integration of the problems in the areas of production, inspection, minimal repair, preventive maintenance, and inventory. It proposes a strategy for maximizing expected profit in an imperfect production system with the possibilities of minimal repair and rework. In today’s world that emphasizes green technology and environmental protection, being able to make defective products reusable means reducing resource waste and can also increase the company’s profit. The deterioration of production systems commonly exists in the manufacturing industry. For this kind of system, understanding the mutual relationships between production, inspection, minimal repair, preventive maintenance, and inventory can help managers to do more efficient operation control and quality assurance to increase their company’s competitiveness.