مدل سازی موجودی محموله برای یک آیتم وخامت در حالی که خریدار محدودیت ظرفیت انبار دارد

In this article, we consider a single-manufacturer–single-buyer supply chain problem in which the manufacturer produces a single deteriorating product and delivers it to the buyer on the basis of a consignment policy. An integrated inventory control model, jointly determining the manufacturer's production batch and the replenishment lot sizes, is proposed to minimize the manufacturer's total cost per unit time. Both scenarios of the buyer with and without warehouse capacity constraint are presented. The characteristics of the model are discussed. In addition, the impacts of the buyer's warehouse capacity constraint on the manufacturer's total cost, production batch, and replenishment lot sizes are also presented through numerical illustrations. This model generalizes those published results and enables managers to move from a reactive mode to a proactive one by taking the supplier's perspective.

This research was motivated by problems encountered in the subject of our case study, Chang Gung Memorial Hospital, a medical center in Taiwan affiliated with the authors’ university. Currently, the hospital's supply chain department utilizes consignment purchasing policy on certain surgical materials used by cardiac, orthopedic, and ophthalmology units. Having gained a lower inventory holding cost and enjoying more flexible cash management in procurement, the hospital's top management would like to extend the consignment program to as many other medical materials as possible. The consignment purchasing policy has been utilized in automotive manufacturing and health care industries for years (Fenton and Sanborn, 1987 and Valentini and Zavanella, 2003). The APICS Dictionary defines consignment as “the process of the supplier placing goods at a customer location without receiving payment until after the goods are used or sold” ( Blackstone, 2008). In the consignment purchasing policy, the buyer provides warehouse space for the supplier to stock, thus allowing the latter generous savings in inventory carrying costs; on the other hand, the buyer can defer payment until those stocks are actually consumed. This implies that a consignment program might create a condition of shared benefits for both the supplier (manufacturer) and the buyer (consignee). As with most consignment agreements, the buyer is responsible for any loss or damage of stocked goods, and the supplier is no longer responsible for storage or material handlings. For this reason, it is no surprise that the supplier would like to stock as much inventory as possible in the buyer's warehouse. In contrast, the buyer would rather stock a lower level of inventory as long as it is sufficient to buffer against demand uncertainty. Thus, how to negotiate and reach an agreement between both parties regarding the consigned inventory levels becomes a critical issue. None of the previous studies have incorporated the major buyer characteristics such as maximum available warehouse space, which may largely impact optimal vendor behaviors in consignment policy. Lee and Wang (2008) were the first to take into account this important factor. They studied the impact of the buyer's warehouse capacity constraint on the manufacturer's total costs, when both the supplier and buyer in the supply chain agree to adopt a consignment purchasing policy. In this paper, we extend our results in Lee and Wang (2008) to a case in which the product is deteriorating. We consider a single-manufacturer–single-buyer supply chain problem where a manufacturer produces a single deteriorating product and then delivers it, in a constant lot size, to the buyer on the basis of a consignment policy. An integrated inventory control model, jointly determining the manufacturer's production batch and the replenishment lot sizes subject to the buyer's warehouse capacity constraint, is constructed to minimize the manufacturer's total cost per unit time.

Consignment purchasing policy is popular and prevalent in manufacturing and health care industries. In this paper, we proposed a joint economic lot size model to simultaneously determine a single manufacturer's production batches of a deteriorating item and replenishment lot sizes to a single buyer under consignment contract. The objective of this inventory model is to minimize the supplier's total cost, subject to the buyer's warehouse capacity constraint. The model developed is realistic and general in the sense in which known results such as Braglia and Zavanella (2003) and Lee and Wang (2008) are special cases of our proposed model. Our findings conclude that the time-weighted inventory on the supplier's (buyer's) side is equal to the units of deterioration loss in the supplier's (buyer's) warehouse divided by its inventory deterioration rate. In addition, when the buyer's warehouse capacity is increasing, the manufacturer's total cost is monotonically decreasing; however, once the buyer's warehouse capacity reaches a threshold, any further increase will not have any effect on the manufacturer's total cost. The proposed model enables managers to move from a reactive mode in a complex consignment supply chain to a proactive one by taking the suppliers’ perspective.