應用限制理論與作業基礎成本法於聯產品決策之研究

A Study on Applying the Theory of Constraints and Activity-Based Costing to Joint Products Decisions

賴建文(Chien-Wen Lai)

指導教授 ： 蔡文賢

國立中央大學/管理學院/企業管理學系/博士(2006年)

摘要

論文摘要內容：
連續性生產程序之企業，相同製程，可同時產出數種不同的聯產品，例如化學業、石油業或肉類加工業，分離點後的聯產品，可能立即出售，也可能經額外加工程序後再出售，是否繼續加工涉及企業有限資源的分配，為使利潤最大，此種決策需考慮繼續加工的邊際貢獻、產能資源限制以及市場需求等因素，本研究應用限制理論及作業基礎成本法，就聯產品之生產特性，從短期、中期及長期等三種不同構面來設計決策模式，以制定最適聯產品組合之相關決策。
為制定短期決策，限制理論假設管理者對人工成本與製造費用無控制能力，並將其視為無需分攤的固定成本，本研究首先根據限制理論，針對不熟悉數學規劃的管理者，設計出一套演算法來制定短期聯產品生產組合決策，此演算法共有七大步驟，透過順位比率的計算，使這些步驟能在決策過程中考慮到所有的瓶頸資源，以便找出可得到最適解的最佳途徑，由於其方便性與易了解性，此種以限制理論為基礎的演算法得以成為制定短期聯產品組合決策的實務性工具。
相對於限制理論，作業基礎成本法研究作業與資源耗用間的因果關係，以提供更正確的成本資訊，在長期構面下，當管理者對人工與製造費用作業資源有完全控制能力時，作業基礎成本法的決策模型可得到極大化的長期利潤。然而在一般的中期決策構面下，管理者對人工與製造費用資源，會有不同程度的控制力，若超額產能無法消除或移作他用，作業基礎成本法的決策模型將高估其利潤，反之，若超額產能可消除或移作他用，限制理論的決策模型將低估其利潤，為將管理者對資源之控制力整合至決策過程，本研究設計出一個較一般化的作業基礎成本法決策模型，以放寬原來模型中的嚴格假設，使管理者能在一般環境下，充分利用其瓶頸資源，以制定最佳中期聯產品生產組合決策。
在長期構面下，當生產聯產品之公司缺乏足夠產能以因應市場需求時，為了滿足客戶訂單與極大化公司利潤，管理者應研究產能擴充與部分產品外包的可行性，針對此項決策，本研究利用數學規劃，透過正確的成本分析，設計出一個作業基礎成本法決策模型，使公司能維持內部生產與外包的均衡，同時透過有效率的資源分配以取得競爭優勢，藉由此模型，生產聯產品之公司可制定有關是否繼續加工、產能擴充或部分產品外包的長期決策。

關鍵字

聯產品 ； 作業基礎成本法 ； 演算法 ； 外包 ； 限制理論

並列摘要

Abstract
A particular decision making process that is needed by most firms who produce joint products is the one requiring an assessment of desirability of further processing joint products beyond the split-off point. Especially in a situation in which market demands exceed the company’s production capacity. The thesis includes three studies to deal the joint products related decision problems from three different perspectives.
In the short-term perspective, an algorithm is developed for optimizing a joint products further processing decision under the Theory of Constraints. Especially for those schedulers who do not be expert in linear programming techniques. To fit the jointly produced characteristic of joint products and the sequentially produced characteristic between each joint product and its further processing product, the algorithm is composed of seven steps. These steps consider every bottleneck resource to the decision-making processes by computing a priority ratio to establish its priority sequence. Basing the priority sequence of the most constrained resource, the initial master production schedule is developed. Then the following steps find the best path to reach the optimal solution under the guidance of all bottleneck resources. Due to its accessibility and comprehensibility, the TOC-based algorithm developed by this thesis is a practical tool for obtaining the short-term optimal decision.
In the medium-term perspective, the thesis models the decision-making processes for the joint products further processing decision with Activity-Based Costing and the Theory of Constraints. However, the stringent assumptions of the ABC and TOC may not exist in the general medium-term decision circumstances. A general ABC model is developed which incorporates management’s discretionary power over labor and overhead resources into joint products further processing decision. With the general ABC model in this thesis, the firms who produce joint products would fully utilize the constraint resources and this would lead to a medium-term optimal joint products further processing decision in most practical environments.
In the long-term perspective, the thesis develops an ABC joint products decision model which incorporates capacity expansions and outsourcing features, by using a mathematical programming approach. With the model presented in the thesis, we can evaluate the comparative benefits of expanding the various kinds of capacity and outsourcing simultaneously. By applying this model, the companies who produce joint products can derive a long-term optimal decision about further processing, capacity expansions or outsourcing.

並列關鍵字

Algorithm ； ABC ； TOC ； joint products ； outsourcing

參考文獻

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