製造商為了滿足市場上消費者對於產品多樣化的選擇，必須不斷研發設計新產品，在研發過程中當然必須考慮到製造程序，在製造程序中又必須加以考慮產線設備的運作狀態。因製造商常會忽略對設備進行維護作業進而導致設備無預警的停機，進而損失既有的產能外也將支出一筆龐大的設備維護費用，所以製造商必須透過設備維護計畫來降低設備失效次數以減少設備的維護費用同時可確保設備的正常運作。本論文為探討製造商產線上的系統設備為雙零件組成的系統設備，考慮雙零件組成方式為並聯與串聯系統兩種形式。雙零件組成的系統設備在運作時發生失效即以小修方式處理，為減少失效次數製造商須規劃預定置換時程進行雙零件系統置換作業，依據上述的維修置換策略，本論文分別建構出並聯與串聯系統的個別置換與群體置換成本模式，尋求雙零件系統之最佳置換時程使得期望單次更新成本率為最低，研究結果可供製造商在規劃產線上的系統設備維護保養計畫之參考依據。

In order to provide consumers with the choice of a variety of products, manufacturers must continue to develop new products. The development process must take the manufacturing process into account and consider the operational status of the production line equipment. Without a proper plan of equipment maintenance, it may cause the unexpected shutdowns of the production line and spend the extra maintenance cost. Therefore, this thesis investigates the case when the equipment of manufacturer is a two-component system which is connected in parallel or series. The replacement policies under consideration are individual and group. When a component fails during the operation, it is rectified by a minimal repair. In order to reduce the number of failures, a scheduled replacement may be required to replace the component preventively at the pre-specified time. Under this maintenance scheme, the mathematical formula of the expected total cost rate for a two-component system is derived, and then the optimal preventive replacement policy is obtained such that the expected total disbursement cost rate is minimized. Finally, some numerical examples are given to illustrate the impact of the optimal preventive replacement on the total disbursement cost rate.

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