考量回廠率下零組件需求預測與備貨模式之研究—以汽車業為例

消費者選購商品時，考慮的因素除了產品本身的品質，也包括了售前和售後的服務品質，而其逐漸重視產品維修及保固的概念，更是帶動了「服務性零組件」產業的興起。服務性零組件如同主產品有其生命週期，每個階段皆有其需求型態，且重視的議題也有所不同。本研究以汽車產業為例，並針對第一階段導入期探討存貨預測模型，於導入期之零組件需求呈現不斷上升的狀態，又缺乏歷史銷售資料作為預測之依據，而需求波動大的特性更使零組件之需求難以估計，因此本研究希望能在符合訂單滿足率的條件之下，減少零組件的存貨總量，並使消費者需求獲得最大的滿足。本研究首先利用最小平方法之概念找出合適的T（車齡基礎單位）以估計各車齡之回廠率，將汽車銷售資料乘上對應之回廠率求出各期預估的回廠總車輛數；得到預估回廠總車輛數後，將此數據當做自變數、實際零組件需求量當做依變數，選擇R2最高的迴歸方法，將預測當期的預估回廠總車輛數代入，即可預估零組件需求量。接著，本研究再以將指數平滑法的概念導入均方誤差中，做為需求端安全庫存量之依據。最後根據零件採購資料，設定平均訂購週期和平均前置時間與變異，規劃出一套完整之汽車零組件定期盤存制存貨模式。與汽車產業中一具代表性之個案公司現行的存貨政策進行比較後，顯示出本研究之需求預測模式能準確評估導入期不斷上升的零組件需求量，在一定的訂單滿足率下大幅減少總存貨量，以相對較少的存貨量滿足顧客零組件之需求，並有效降低庫存成本。

關鍵字

服務性零組件；零組件生命週期；需求預測；回廠率

並列摘要

When buying the products, consumers consider not only the quality of the products but also the before-sales and after-sales service. They put more emphasis on the maintenance and warranty. Therefore, service parts industry becomes more and more important and inventory issues of service parts industry become much popular than before. Service parts are like the products that have the life cycles. This thesis focuses on the phase-in period of the service parts to reduce the total inventory under the high fill rate when the demand of service parts is increasing during this period. First, in order to calculate to return rate to factory service, we use the concept of least square method to find a T. Multiplying factory return rate by corresponding sales amount is the estimated total amounts of returning automobiles for each period. Then, use the regression method with highest R2 to forecast demand of service parts. Second, introduce exponential smoothing method into mean square error to be the basis of safety stock. Finally, according to the service parts procuring data, we can find the average order cycle, average and lead time and variation of lead time, and build a complete auto service parts periodic inventory model. Comparing with the performance of the model H Company using, new demand forecasting model can forecast more accurately the increasing demand in phase-in period and reduce the total inventory amounts with high fill rate. By means of new forecasting model, H Company can satisfy the customers’ demand of service parts with less inventory amounts and lower the cost of inventory.

並列關鍵字

service parts ； parts life cycle ； demand forecasting ； return rate to factory service

參考文獻

1.林翰輝，考慮需求不確定下庫存管理模式—以汽車維修零件為例，國立台灣大學商學研究所碩士論文，2007

2.吳沛軒，考量零件生命週期下汽車售後零組件需求預測與備貨模式，國立台灣大學商學研究所碩士論文，2008

3.陳育珊，考慮產品生命週期末端之服務性零組件最後訂購模型—以汽車產業為例，國立台灣大學商學研究所碩士論文，2009

4.滕喆安，服務性零組件最後訂購情況下最適服務水準之研究－以汽車產業為例，國立台灣大學工業工程研究所碩士論文，2009

5.John R. Moore, J.R., “Forecasting and Scheduling for Past-Model Replacement Parts”, Management Science, 18, 4, (1971), 200-213

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考量回廠率下零組件需求預測與備貨模式之研究—以汽車業為例

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