在風險環境下考量供應商異質性的供應商選擇模型

此研究係探討當供應商的價格、品質、交期等條件具有異質性時，買方該如何取捨，以極小化本身的總攸關成本。Ruiz-Torres & Mahmoodi (2007)考量個別供應商失敗機率不等的情況，針對買方提出最佳的供應商選擇模型，惟其模型中未考慮品質與交期二項重要的選擇標準，亦未能進一步決定個別供應商的訂購量，並運用商用軟體快速求解。本研究運用決策樹方法(decision tree approach)建立一般化的數學模型，用以決定應選擇那些供應商，以及個別供應商的最佳訂購量。本研究模型除了改善RM模型的不足之處，同時也利用實際的例子清楚說明買方總攸關成本的組成項目，包括預期損失成本與預期營運成本，進而協助買方決定原料的合理採購價格，並選擇合適的供應商，以極小化總攸關成本。研究結果顯示，雖然低廉的進貨價格可以節省預期營運成本，但供應品質不佳通常也會產生較高的預期損失成本；因此，管理者應衡量其中的替換效果來選擇供應商。最後，我們以台灣某光罩製造商為例，經由所提之模型運算後，將該公司的供應商報價分成四個階段，並分別說明各階段的最佳供應商選擇策略，同時，我們也證明一味地增加供應商數目未必有助於總成本之節省。

關鍵字

供應商選擇；原料取得；風險分析；採購管理

並列摘要

The purpose of this research is to investigate how buyers find the appropriate suppliers from the presence of heterogeneity in supply terms, including price, quality, delivery and so on by considering minimal total relevant cost. Buyers' total relevant cost were separated into expected loss cost and expected operating cost. They had taken into consideration the different levels of failure risk for suppliers and proposed models to determine the optimal number of suppliers. However, their models did not involve quality and delivery, two critical standards in supplier selection. In addition, these models cannot be used to determine the order quantity and rapidly solved by LINGO. We utilize the decision tree approach to develop a mathematical model. The proposed model can be easily applied to determine which suppliers should be selected and how many units should be purchased from them. We not only resolve the drawbacks in the existing models, but also illustrate the compositions of total relevant cost, including expected loss cost and expected operating cost, to help buyers to determine the appreciate suppliers under the minimization of the total cost. The results indicate that lower acquisition prices may imply worse quality and delivery and result in higher expected loss cost although they decrease the expected operating cost. Therefore, managers ought to evaluate the effect of trade-off to determine the suppliers. Finally, the application of suggested model is demonstrated through a photo mask manufacturer in Taiwan. We divide the supplier's quoted price into four intervals and individually show the best strategy of supplier selection. Moreover, we also prove that increasing the number of suppliers is not necessarily a good policy for total cost reduction.