Tabu search-based algorithm for the TOC product mix decision

The theory of constraints (TOC) is a management philosophy that maximizes profits in a manufacturing plant with a demonstrated bottleneck. The product mix decision is one application of TOC that involves determination of the quantity and the identification of each product to produce. However, the original TOC heuristic is considered to produce unrealizable solution when a manufacturing plant has multiple resource constraints. This paper presents a tabu search-based TOC product mix heuristic to identify optimal or near optimal product mix for small problem instances under conditions where the original TOC heuristic failed. The tabu search-based TOC product mix heuristic is further used to solve large problem instances typical of practical manufacturing scenario. The experimental results for small to medium size problem show that the tabu search-based TOC heuristic compares favourably with those of optimal methods. Large size problems for which optimal methods have not been established in terms of feasibility in computation times were also solved in reasonable times with good quality solutions, thus confirming that the proposed approach is appropriate for adoption by production planners for the product mix problem in the manufacturing industry.     

Introducing in-between decision points to TOC’s five focusing steps

This paper builds on the original five focusing steps as defined by Goldratt and Cox (1992) as one of the constructs of the theory of constraints (TOC). The shortcomings identified are the sequential nature suggested by the five seemingly sequential steps, the lack of clarity relating to decisions that allows moving to next or previous steps, the assumed inapplicability of the five steps to dealing with market- and non-physical constraints (such as policy and behavioural constraints) and the lack of clarity surrounding an ideal constraint location. Deductive reasoning is applied to existing literature to arrive at conceptual solutions to the identified problems. The paper transforms the five focusing steps into a decision map which still includes all five steps, but allowing appropriate decision points to guide application of this process. It expands the applicability of the five focusing steps to both market and non-physical constraints, as well as presenting a logical argument why the best possible constraint location is ‘the size of the market chosen to be served well’. Finally, further clarity is provided why exploiting and subordinating to the constraint is necessary before constraint elevation should take place.     

Implementing theory of constraints in a traditional Japanese manufacturing environment: The case of Hitachi Tool Engineering

This research presents a case study of a virtual ‘textbook’ application of the theory of constraints (TOC) in a Japanese tool manufacturing company. Hitachi Tool Engineering uses state-of-the-art technology to design and manufacture cutting tools known as End-mills. The plant described in this study is a classic V-plant and exhibited all of the standard problems of a traditionally managed V-plant, existing within the unique framework of Japanese work culture. Plant management applied the five focusing steps and used the operations strategy tools, including drum-buffer-rope and buffer management, to improve the system. Following the approach recommended by Eli Goldratt, the thinking process tools of current reality tree and evaporating clouds were used to help identify and resolve problems when the implementation encountered major obstacles. While the implementation was a huge success, the devastating effect of a core problem being left unresolved is well documented. The implementation generated significant improvements in work-in-process inventory, production lead time, on-time delivery, productive capacity, inventory turnover, product quality, sales volume, and profitability. Moreover, management has extended the introduction of TOC to the non-manufacturing functions and TOC is becoming the common company culture that bridges four culturally diverse manufacturing plants.     

Information technology in operations management: a theory-of-constraints approach

The theory of constraints (TOC) has recently gained much success in its application to industrial and service organizations. This paper applies the TOC principles to the management of information technology (IT) in the organization. The paper creates a four tiered model for the application of the TOC to IT, starting with TOC's throughput-driven business policy; on with the seven step resource management methodology; through the cost/utilization capital investment technique; and concluding with the drum-buffer-rope production activity procedure. We draw a framework and a methodology showing how IT can be more effective using the TOC way of management. In order to systematically explore the location of the organization's constraints we adapt to the TOC a synthesis of three established management frameworks: stakeholder analysis, the value chain and Boston Consulting Group's portfolio analysis model     

基于瓶颈的产品组合决策方法

产品组合决策关系到企业的效益。本文基于约束理论中确定瓶颈的方法,针对约束理论关于产品组合决策方法在多约束条件下的不可行性,提出了一种同时考虑主约束和最大次约束的启发式方法,分为五个步骤对其进行了详细的说明。文中还通过实例仿真来说明了新方法的可行性及简单、易用性。     

基于TOC的业务外包决策模型研究

建立了业务外包决策问题的数学模型,阐述了标准约束理论下业务外包决策过程,指出了多瓶颈情形下标准TOC方法的不足,提出了集成作业成本法的改进模型,较好地解决了多瓶颈问题,分析了新模型制定短期决策和长期决策的侧重点.实践证明,新模型制定的业务外包决策比标准TOC方法模型更合理有效,企业获取的利润更大.     

Performance of decomposition procedures for job shop scheduling problems with bottleneck machines

Decomposition procedures for job shop scheduling problems, such as the shifting bottleneck (SB) procedure, have shown promising results for a variety of shop environments. However, they have primarily been tested using problems where all machines are identical in terms of processing time distribution. Many practical scheduling problems involve bottleneck machines which become the focus of scheduling efforts, as suggested by the theory of constraints. In this paper we examine the performance of several variants of SB, some of which can be interpreted as naive implementations of the TOC approach to scheduling. Our results show that both the solution time and quality of SB methods improve markedly when bottleneck workcentres are present. However, scheduling bottleneck machines optimally and using simple rules at other machines leads to poor performance unless the workload of the bottlenecks significantly exceeds that of the non-bottleneck machines.     

基于制约的时间管理理论研究

针对作业成本法和制约理论的缺陷,同时利用二者的互补性,提出了基于制约的时间管理理论。在决策方面,该理论结合了作业成本法与制约理论的优点,通过分析特定环境下系统的时间、成本与现金收益之间的关系进行决策。在持续改善方面,该理论以制约理论为基础,结合作业成本法的作业分析技术以合理确定制约并对制约进行分类,通过对不同类型的制约采取不同的步骤以实现持续改善：对于非稳定制约,应采取措施尽快提升制约,使之发生转移;对于稳定制约,应在提升制约的同时,使非制约的行为服从于制约。     

A CBFSA approach to resolve the distributed manufacturing process planning problem in a supply chain environment

In this competitive world cost and lead time reduction are of prime concern for manufacturing firms. To achieve this objective manufacturing entities are adopting several management philosophies such as Total Quality Management (TQM), just-in-time (JIT), and theory of constraints (TOC). The present paper addresses the advanced computer-aided process planning (ACAPP) problem in a distributed manufacturing supply chain environment and aims at cost and lead times reduction under several technological constraints. To deal with the complexity of the problem the constraint based fast simulated annealing (CBFSA) algorithm has been explored in this article. Extensive computations have been performed over the well-known benchmarks of advanced planning problems and the results obtained prove the superiority of the proposed algorithm over the prior approaches.     

TOC构造过程模型驱动产品创新设计

简要分析了产品冲突问题的约束理论(theory of constraints,TOC)思维流程,介绍了发明问题解决理论(theory of inventive problem solving,TRIZ)创新设计过程。描述了TOC中5个逻辑图表及其相互之间的关系。提出一种将TRIZ与TOC相结合的产品冲突问题解决过程构造模型的设计方法,利用所构造的产品当前实现树、逻辑图表和TRIZ的矛盾冲突解决矩阵来解决产品冲突问题。实例证明TRIZ与TOC相结合的方法用于驱动产品创新设计是切实可行的。     

制约理论在管理会计中的应用一例

制约理论是当今美国和欧洲比较流行的一套管理哲理和持续改进方法。通过实际案例，根据Goldratt的5个关键步骤，找到系统的制约，利用开发和释放制约从而使系统的整体能力得以提高。     

Composition of module stock for final assembly using an enhanced genetic algorithm

The paper focuses on modelling and solving a design problem, namely the selection of a set of modules to be manufactured at one or more distant sites and shipped to a proximity site for final assembly subject to time constraints. The problem is modelled as a mathematical one, and solved by an appropriately designed genetic algorithm enhanced with a modified crossover operation, a uniform mutation with adaptive rate and a partial reshuffling procedure. The actual design problem is solved with 17 components. Larger problems may be solved without modifying the modelling steps, although they may require variation in terms of processing time, depending on the constraints that exist between the components.     

Formulation and solution of the drum-buffer-rope constraint scheduling problem ( DBRCSP)

This paper seeks to advance the current understanding of constraint scheduling in several ways. First, it describes the need for constraint scheduling in DBR systems. It then formally presents the production scheduling problem DBR attempts to solve and relates that formulation to prior research. Finally, it evaluates the quality of solutions produced by the solution algorithm incorporated by the Goldratt Institute (and now maintained by the TOC Center's Goal Systems Group) in their production software on a set of benchmark problems involving multiple constraints. The results show that generally good results can be obtained as long as the constraints are scheduled in the best sequence.     

Performance measurement in a theory of constraints environment

There is an increasing recognition of the critical role played by an organization's performance measurement system in achieving competitive success. The success of an organization may well depend upon the compatibility between the performance measurement system in operation at subordinate organizational levels and the organization's global goals. An increasing amount of research in operations management addresses the relationship between the operation's performance measurement system and its apparent incompatibility with global organizational goals. The performance measurement system associated with the theory of constraints (TOC) has been advocated by some researchers as a mechanism for linking operational objectives to the global goals of an organization. However, empirical research is lacking to determine and test the relevance of the proposed performance measurement system presented in TOC. This study examines the application of a TOC-based performance measurement system in an operating environment and reports on the results. A set of propositions are also provided to further future research.     

A simplified approach to solve quasi-statically moving load problems of elastica using end loaded elastica solution

Elastica problems with non-conservative moving forces are more complicated as compared to end loaded elastica problems. Established methods exist to solve an end loaded elastica problem. For solving a moving boundary problem, such methods need considerable modification or re-formulation. In this article, results of an end loaded elastica problem which is readily obtainable are used to solve two relatively involved moving boundary cases. The solution methodology involves a unique normalization procedure for the available elastic solution followed by few simple steps. One of the problems considered is three point bending of elastica with finite roller dimension. The other one being cantilever elastica under the action of wedge contact. Structural stiffening is observed in both the cases as a result of moving boundary condition as compared to when roller dimension is negligible or wedge makes only point contact. A structured approach may potentially originate from this kind of procedure to tackle more complicated moving boundary problems of elastica.     

Theory of constraint methodology where the constraint is the business model

This paper addresses the issue of business model (BM) management and its relationship to the theory of constraints (TOC). Coman and Ronen (Coman, A. and Ronen,B., 2007. Managing strategic and tactical constraints in the hi-tech industry. International Journal of Production Research, 38(7), 1631–1639) have extended TOC methodology to include the alignment of the organisation's competencies with the business arena's strategic constraints. The aim of this paper is to take TOC one step further and to combine it with the business models theory. Business models have become important value creators due to the proliferation of new and innovative business models (i.e. new ways of creating value). New firms with new business models are threatening and replacing established companies and conventional ways of doing business. Among these are the music, publishing, books, retail, airline and many other industries. This paper argues that in the wake of the World Wide Web, contract manufacturing and globalisation it not enough to manage the firms (internal, external or strategic) constraints. In addition, the management of the firm's BM as a potential constraint is a key factor in the modern management theory.     

Minimum cost design of framed structures by the mini-max dual method

Minimum cost design of a framed structure is considered by using the mini-mas dual method. Stress and/or displacement constraints are imposed as behavioural constraints. The minimum cost design problem has a discrete objective function and discrete design variables. A sequence of approximate optimization problems in created by using the first-order Taylor series expansion for displacements with respect to the reciprocals of cross-sectional areas and moments of inertia. Each approximate problem is solved in the dual space. Two simple structural examples are given to show the appropriateness and efficiency of the proposed procedure. Approximate solutions are obtained within five structural analysis.     

When less is better: Insights from the product mix dilemma from the Theory of Constraints perspective

Perhaps due to its origins in a production scheduling software called Optimised Production Technology (OPT), plus the idea of focusing on system constraints, many believe that the Theory of Constraints (TOC) has a vocation for optimal solutions. Those who assess TOC according to this perspective indicate that it guarantees an optimal solution only in certain circumstances. In opposition to this view and founded on a numeric example of a production mix problem, this paper shows, by means of TOC assumptions, why the TOC should not be compared to methods intended to seek optimal or the best solutions, but rather sufficiently good solutions, possible in non-deterministic environments. Moreover, we extend the range of relevant literature on product mix decision by introducing a heuristic based on the uniquely identified work that aims at achieving feasible solutions according to the TOC point of view. The heuristic proposed is tested on 100 production mix problems and the results are compared with the responses obtained with the use of Integer Linear Programming. The results show that the heuristic gives good results on average, but performance falls sharply in some situations.     

Cost minimization of 2D continuum structures under stress constraints by increasing commonality in their skeletal equivalents

It is well known that, for real-life engineering problems, minimum weight does not necessarily mean minimum cost, thus it is of practical value to simultaneously achieve both layout optimization and cost minimization of a structure. Towards this direction, the present paper discusses a procedure of four steps concerning 2D continuum structures under stress constraints only. The continuum is first substituted by an equivalent skeletal structure, which is then optimized using the Sequential Quadratic Programming (SQP) technique. In the sequel the optimized structural members of equal or near-equal cross-sections are appropriately grouped and finally all optimized structural members of imposed critical minimum or near-minimum cross-section are eliminated. Both grouping and elimination procedures were based on a simple statistical manipulation. The proposed procedure was applied to four test cases, namely the short and long cantilever, the MBB beam and the L-shape beam. The conclusion of the present work was that, for 2D continuum structures under stress constraints only, the proposed procedure provided the means for both layout optimization and structural cost minimization.     

TOC-based performance measures and five focusing steps in a job-shop manufacturing environment

Theory of constraints (TOC) views a company as a set of interdependent processes working in harmony to achieve the profit goal of the company as a whole, and thus it emphasizes total system performance over localized measures to guide operational decisions. This paper demonstrates the usefulness of employing TOCbased global performance measures to make operational-decisions (e.g. product mix, continuous improvement, inventory management, production planning and scheduling) to strengthen the internal supply chain in a relatively complex manufacturing environment, i.e. a job shop. An ARENA-based simulation model is presented and a number of scenarios are discussed that provide insights regarding the characteristic features of TOC, such as goals and necessary conditions, performance measures, five-focusing steps for continuous improvement, and drumbuffer-rope scheduling. These insights will assist managers in making important decisions regarding approaches to successful TOC implementations, and will provide academics with a broad range of future research opportunities.