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  • 學位論文

探討經濟批量排程問題下報廢品與重工之整合性生產與產品檢視模式研究

Integrated Production and Inspection Models with Scrap and Rework in the Economic Lot Scheduling Problem

指導教授 : 宮大川
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摘要


本研究探討多個產品在單一生產設備上產品檢驗策略與重工與否之經濟批量排程問題(Economic Lot Scheduling Problem, ELSP)。傳統的經濟批量排程問題假設生產程序是完美的,但由於生產設備往往會隨著時間而性能衰退,變得不穩定,而產生一定比例的不良品,故此假設在實務上並不可行。因此,建置不良品檢驗程序與何時建置不良品檢驗程序更形重要。除此之外,針對不完美的生產程序所產生的不良品是否考慮重工的問題,亦是一重要課題。本論文在考慮不良品是否重工的前提下,分別針對三種建置不良品檢驗程序的策略,探討不良品報廢、不完美修復與缺貨問題對經濟批量排程問題的聯合影響 假設生產之初,生產設備是處於操控狀態。但隨著時間的增加,生產設備因為性能衰退,會隨機的轉為失控狀態,因而產生一定比例的不良品。本論文假設兩種處理此些不良品的方式:(1)全部視為報廢品,予以丟棄,不能重工;(2)部分不良品視為報廢品,部分不良品則可以重工;但仍有部分重工件因修復失敗而報廢。在第一種不良品的處理方式下,根據不良品的檢驗策略,可以分為: (1a) 不檢驗不良品;(1b)在生產程序結束後,始檢驗不良品;(1c)在生產過程中100%檢驗不良品。在第二種不良品的處理方式下,亦有三種不良品的檢驗策略:(2a)考慮在不檢驗不良品的情形下,在存貨耗盡前/後進行不良品的離線重工;(2b)在生產程序結束後,進行不良品的檢驗,檢驗完後,始進行不良品的離線重工;(2c)在生產過程中100%檢驗不良品,生產完後,始進行不良品的離線重工。 本文利用共同週期法求解不完美生產系統下多樣產品之經濟批量排程問題,目標是求解一個最佳化的共同週期時間使得每單位時間的期望總成本最小。本研究提出一個求解程序,以求得一個近似最佳解,並且在目標方程式中代入指數方程式的近似式以推導封閉解,再利用基因演算法驗證本研究所提出的求解程序的有效性。最後利用數值範例以說明最佳化的共同週期時間的推導。同時從此些數值範例中可以看出生產程序愈不可靠,共同週期時間則愈短。在不考慮重工的狀況下,若是可靠的生產製程,則宜採取不檢驗不良品策略;若生產製程不可靠,則宜採取生產程序結束後始檢驗不良品的策略。但在考慮重工的狀況下,則宜採取不檢驗不良品的策略。

並列摘要


In this research, we consider the imperfect production processes of the Economic Lot Scheduling Problem (ELSP) which deals with multi-product produced on a single production facility. The basic assumption of the classical ELSP model is that the production process is perfect. In fact, this assumption may not be valid for most of the manufacturing environments. Owing to aging, many production processes may deteriorate to produce defective products. Due to imperfect production processes, decisions regarding whether and when to implement a screening process are typical of every inventory problem. Besides, rework of defective products, which may eliminate waste, reduce disposal costs and comply with environmental legislation, is also an important topic. This research is concerned with the joint effect of scrap, imperfect repair, and shortage on the ELSP involving three types of screening processes with or without rework considerations. In general, a production facility is assumed to be in control at the start of a production run. Owing to aging, it may deteriorate and shift at a random time to an out-of-control state, and consequently produces a fixed fraction of nonconforming items. There are two situations to handle the defects in this research: (1) these defective items cannot be repaired or reworked, and thus must be scrapped with an additional cost; (2) some proportion of defective items cannot be reworked and must be scrapped. The rest of these defective items can be reworked off line. However, since the repair process is imperfect, scraps are produced during the manufacturing and/or rework processes. In the first situation, three models are presented to consider whether and when to implement a screening process, which are: (1a) no screening process, (1b) after-production screening, and (1c) in-production screening. On the other hand, there are several models are proposed in the second situation with various screening options that are (2a) under no screening process with repair before/after depletion, (2b) after-production screening with repair right after screening, and (2c) in-production screening with repair right after production. In this research, a Common Cycle (CC) approach is applied to solve ELSP under imperfect production process. The objective is to determine an optimal common production cycle time that minimizes the expected total cost per unit of time. A solution procedure is developed to find near-optimal solutions for the models. By approximating exponential functions included in the objective functions, certain closed-form solutions can be developed. A genetic algorithm heuristic is implemented to verify the effectiveness of the solution procedure we proposed in this dissertation. Numerical examples are presented to illustrate the derivation of the optimal common production cycle time. These results show apparently that the less reliable a production process is, the shorter a production common cycle time should be. Without rework considerations, strategy without screening is properly adopted when the process is reliable. As the process becomes less reliable, after-production screening process is implemented. On the other hand, with rework considerations, strategy without screening is properly adopted.

參考文獻


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