مدل مقدار تولید اقتصادی برای محصولات رو به وخامت/ ناقص و خدمات با دوباره کاری

In this paper, two economic production quantity (EPQ) models are proposed for deteriorating/imperfect items with rework process. The production process is imperfect, and imperfect quality items are reworked to become serviceable. At the same time, the remaining good quality items may deteriorate. The inspection of deteriorated items is also imperfect, so that deteriorated items may be sold to customers, which will create negative impact on corporate image. In the first model, a single production-rework plant system is considered. The optimal production times and the economic production quantities are obtained analytically. In the second model, a system that consists of n production plants and one rework plant is considered. A solution procedure is developed in order to obtain the optimal operating cost. Numerical examples are provided to compare the performance of the two systems.

Serving high quality products and providing good service can always attract customers and keep them coming back. However, in reality, production processes are often imperfect. For economic and environmental reasons, imperfect quality items are reworked to become serviceable again. Due to unsuitable inventory condition or other reasons,the remaining good quality items stored in inventory face deterioration. In order to provide good service to customers, inspection is carried out to screen out deteriorated items. However, such inspection may not be perfect and only part of deteriorated items can be screened out. The remaining deteriorated items will then be sold to customers. It will lower customer satisfaction and is harmful to corporate image (Abratt and Mofokeng, 2001 and Smith and Taylor, 2004).

In this paper, two economic production quantity (EPQ) models were proposed for deteriorating/imperfect quality items with rework process. The inspection process for deteriorating items was assumed to be imperfect. We first developed a model for a single production plant system which is also capable of processing rework. The approximated optimal cycle length and total operating cost per cycle were obtained. The economic production quantity was analytically presented. We then developed an aggregated model for a system that consists of n local production plants and one central rework plant. Two cases of rework processes were discussed and a solution procedure was developed. Numerical examples were provided to illustrate the solution procedure. Sensitivity analyzes were also conducted in order to present the implications and insights of the proposed models. The results suggested that under certain scenarios, separating the rework capability from the production plants may reduce the total operating cost.