供應商代管庫存與跨國供應鏈模式之探討：以緊固件產業為例

Exploring VMI and international Supply Chains: A Case of Fastener Industry

供應商代管庫存（Vendor Managed Inventory, VMI）模式，始於80年代中期威名百貨（Wall－Mart）與寶僑（P&G）的合作。藉由供應鏈成員彼此之資訊分享與協同合作，以VMI模式協助整體供應鏈降低成本、加快回應速度、提升營運效益及客戶服務滿意度。緊固件（Fastener）為螺絲、螺帽、鉚釘等結合性零件之泛稱，在存貨價值分類中屬於C類產品，其產品生命週期亦較長，適合實施VMI模式。美國緊固件產業於90年代中期導入VMI模式，並於97年由臺灣緊固件業第一大出口貿易商：友信國際股份有限公司首先導入臺灣。
本研究以友信為研究個案，針對緊固件跨國供應鏈之企業動態模式，做傳統客戶自管庫存模式（CMI）與VMI兩種管理模式之比較，並在各種情境下作模擬分析。首先是四種需求型態下，傳統安全庫存配置之模擬分析。其次是梯狀突增需求下之最佳化庫存配置模擬分析。最後是不同客戶交易條件下，供應商庫存最佳化配置模擬分析。
存貨與斷線為緊固件業經營上之兩大風險，存貨多寡直接反應成本增減；缺料所造成客戶生產斷線不僅必須支付停產罰款更可能失去客戶。因此本研究以存貨持有成本、存貨週轉率與訂單達成率為執行VMI模式之關鍵績效指標。模擬實驗結果顯示，由海外客戶及整體供應鏈之角度，VMI供應商代管庫存營運模式之營運績效均優於傳統模式，尤以海外客戶績效改善幅度最為顯著。同時經由此模型之建構，亦能夠協解決國內業界在VMI推廣與缺乏風險評估的問題。

Vendor Management Inventory (VMI) is one of the most widely discussed partnering initiatives for improving multi-firm supply chain efficiency. Also known as continuing replenishment or supplier-managed inventory, VMI became popular in mid -1980’s, pioneered by the famous retailing case of Wall-Mart and Procter & Gamable. Through sharing inventory information and collaborating work in procurement, VMI allows suppliers manage inventories for their customers, thus streamlining the entire supply chain process and leading to cost reduction for the overall supply chain. VMI can apply to a product with large transaction volume and relatively long product life cycle, and the fastener industry falls into this category. VMI was first implemented in the fastener industry in the early to mid-90’s, and later was applied in Taiwan by QST International. Considering the system dynamic model of international fastner supply chain, a case study of QST was conducted in this article. The purpose is to compare VMI with the traditional inventory management practice. The comparison is based on simulation experiments in various scenario designs. By setting up a safety stock environment, this study first examined supply chain performance in four different demand patterns. Then the supply chain performance was assessed by simulating a precipitate demand increase. This study finally addressed the supply chain performance in different terms of transaction with overseas customers. Inventory cost and shut-down penalty are two major risks in fastener business operation. The amount of inventory has a direct influence on cost in the supply side. Material shortage will have customers shut down their production line, and suppliers in turn face penalty and loss of faith. Consequently, this article selects inventory cost, inventory turnover rate and order fulfillment rate as the key performance index (KPI) as the comparison criteria. The findings based on the simulation experiments indicated that optimum replenishment parameters of VMI model are established through scenarios design, dynamic simulation, parameters tuning and KPI measuring. Furthermore, a systematic modeling approach provides Fastener VMI players with feasible methodology in solving real world VMI problems.