含可控制參數及服務水準限制式的連續性檢查存貨模型之研究

從1970年初，及時(JIT)生產管理系統開始在日本製造業引起廣泛的重視後，由於它對於消除浪費，提高生產力及提升產品品質有極卓越的表現，引起歐美及台灣製造公司爭相仿效與研究。其理念乃是認為透過持續不斷的學習與努力可改進系統中造成浪費的因素，進而使浪費減至最低。欲達成JIT的目標，投資資金以降低訂購成本、縮短前置時間、改善製程品質水準等活動，被認是可行且有效的方法。因此，在以往文獻探討中常被視為不可控制的參數，如訂購成本、製程的品質水準及前置時間等，在實務中其實是可以透過投資資金加以控制的。另一方面，在實際的存貨問題中，缺貨成本常包含契約規定的缺貨懲罰成本，顧客因缺貨造成不便而對銷售商要求數量折扣，商譽的損失以及失去潛在顧客而引起的損失等。這些因為缺貨而引起的諸多成本及損失往往難以精確的估計。本論文係研究在採用服務水準限制式替代目標函數的缺貨成本項下，探討訂購成本、製程品質水準如何透過投資資金加以控制，以及降低訂購成本與縮短前置時間兩者之間的關係並非獨立，建構六個存貨決策模型，其中共同的決策變數有訂購數量、請購點與前置時間。第二章將目標函數中的缺貨成本項以服務水準限制式替代，討論投資資金以降低訂購成本與縮減前置時間的存貨模型。第三章建構一個含服務水準限制式，在製程不完備的情形下，討論如何改善製程品質水準及縮短前置時間的存貨模型。第四章建立含服務水準限制式及在製程不完備的情形下，考慮訂購成本的降低與前置時間有關(包含訂購成本與前置時間之間的關係為線性關係和對數關係)的存貨模型。在每一章利用演算法找出使全年期望總成本有最小值的最適解。

關鍵字

存貨；前置時間；服務水準；品質

並列摘要

The Japanese experience of using Just-In-Time (JIT) production shows that there are advantages and benefits associated with their efforts to control lead time. Japanese manufacturers are known for their strong and lasting partnership with their suppliers. This helps reduce lead time and is one of the sources of success of their JIT philosophy. The successful JIT is through the various effects and continuous improvements that efficient usage of resources the high quality products in the most economical manner, so as to gain the competitive advantages for business enterprise. Many activities, such as reducing the setup cost, shorting the lead time, and improving the quality of production processes and products, are recognized as the feasible and effective ways to achieve the goal of JIT. In other viewpoints, the factors (setup cost, lead time, and quality) mentioned above are often assumed as fixed constant and uncontrollable in the traditional inventory models, but are controllable in practice. On the other hand, in many practices, the stockout cost often includes intangible components such as loss of goodwill and potential delay to the other parts of the inventory system, and hence it is difficult to determine an exact value for the stockout cost. In this thesis, we employ a service level constraint to replace the shortage cost in the objective function, and discuss the problem. In chapter 2, we discuss the problem the problem of investing capital in reducing setup cost, where the setup cost is treated as one of the decision variables in the model. In chapter 3, we further consider the possible relationship between quality and lot size, and investigate the quality improvement problem in which the quality level is viewed as a controllable factor and is one of the decision variables. In chapter 4, we assume lead time and ordering cost reductions act dependently, and discuss the same problem as in chapter 3. For all models proposed in this thesis, we utilize the numerical examples to illustrate the effects of inventory systems associated with investing capital in changing the values of parameters.

並列關鍵字

Inventory ； Lead Time ； Service Level ； Quality

參考文獻

[3] Chung, K. J. and Chiu, P. P. (1998), “Economic Production Quantity Model Involving Lead Time as a Decision Variable,” Master thesis, National Taiwan University of Science and Technology.

[1] Ben-Daya, M. and Raouf, A. (1994), “Inventory Models Involving Lead Time as Decision Variable,” Journal of the Operational Research Society, Vol. 45, No. 5, pp. 579-582.

[2] Candace, A. Y. (1987), “Planned Leadtimes for Serial Production System,” IIE Transactions, Vol. 19, No. 3, pp. 300-307.

[4] Gallego, G. and Moon, I. (1993), “The Distribution Free Newsboy Problem: Review and Extensions,” Journal of the Operational Research Society, Vol. 44, No. 8, pp. 825-834.

[5] Hariga, M. and Ben-Daya, M. (1999), “Some Stochastic Inventory Models with Deterministic Variable Lead Time,” European Journal of the Operational Research, Vol. 113, pp. 42-51.

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含可控制參數及服務水準限制式的連續性檢查存貨模型之研究

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