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27Бережливое производство (Lean) и Теория Ограничений (ТОС). Может ли Теория ограничений быть частью концепции Бережливого производства?
Мухина Мария Владимировна
магистр, ведущий специалист по закупкам, компания «Русские Газовые Турбины», maria.v.mukhina@gmail.com
Литература по менеджменту предлагает различные методики улучшения производительности предприятий, тогда как руководители компаний зачастую хотели бы иметь одну универсальную методику, которая могла бы предоставить все необходимые ответы и решения. Однако, остается нерешенным самый главный вопрос - какая методика лучше других и какую методику руководителю компании выбрать. Данная статья анализирует концепцию бережливого производства (Lean) и Теорию Ограничений (ТОС), что в них похожего, а чем они отличаются друг от друга и также, чем данные концепции дополняют друг друга. Данное исследование основано на обзоре научной литературы, где Lean преподносится как теорема, не требующая доказательств, тогда как ТОС - иногда сомнительная теория с малым количеством подтвержденных результатов. Аналитическая часть статьи представляет собой способ интеграции ТОС в Lean и, кроме этого, аргументы в пользу того, что ТОС на самом деле является неотъемлемой частью Lean. Будущие возможные научные исследования в смежных областях по настоящей теме завершают данную статью. Ключевые слова: TOC, Теория Ограничений, Lean, Бережливое производство, JIT, Точно в срок, производство
Introduction
Due to the emergence of global competition in last century, the manufacturing companies started to study and implement new improvement approaches [24]. Lean production principles developed by Japanese engineers in the 1940s, have become a basis for popular lean concept being an effective approach for cost reduction through the elimination of needless activities or elements in production. Production systems have come a long way from Ford's mass production to lean production [20]. Crute at al. (2003) call the current era the "Lean production era" due to its spreading from automotive sector to all manufacturing industries, for example aerospace, with such giants as Boeing, Airbus, BE Aerospace, Rolls-Royce etc. that implemented the concept. Furthermore, lean improvements are supported by national research programs, for instance in the USA and UK [4].
The evolution of the Theory of Constraints (TOC) started in the late 1970s by Dr. Eliyahu M. Goldratt, Israeli physicist, who first named his theory Optimized Production Timetable (OPT), later to Optimized Production Technology and finally to TOC [15]. However, quick adaptation of OPT in the USA after its presentation in 1980 revealed lack of its understanding and, consequently, failures concerned with that. The mentioned failures forced Goldratt to publish "The Goal", explaining the main principles and techniques of TOC, the first book of TOC's series [18]. Further studies of TOC have led to ambiguous results: Naor at al. (2013) claim that TOC is a good practical approach needed to be "embraced as a scientific body of knowledge" and write about the lack of a theoretical foundation for TOC; some scholars question the novelty of TOC and argue that TOC is more a philosophy than an established theory [15, 18] try to summarize the literature and results on TOC implementation due to its absence until 1998, concluding that the links between TOC and other theories are to be examined; other scholars compare TOC with JIT, MRP, Six Sigma, ABM [7, 8, 9, 19, 22, 25]. Their conclusions are generally the same: further research is required.
Company managers are interested more in practical application of techniques and their results rather than in scientific aspect of theories, desiring to have one multi-purpose approach solving all the issues. Nave (2002) addresses the question on what methodology of TOC, Six Sigma or Lean a company should choose, pointing out that methodology selection is dependent on the company's culture.
Reviewing the literature on TOC and Lean shows an interesting trend of various scholars and practitioners trying to compare TOC with Lean, aiming to find the best applicable technique. The mentioned comparisons revealed distinctive features of TOC and Lean used further in this paper. However, the nature of "the best" is doubtable from the beginning, as everyone has their own opinion and understanding of "the best". Hence, the paper is focused on incorporation of TOC and Lean, providing arguments that the nature and purpose of TOC and Lean are intrinsically the same. The comparison presented in the paper target combining TOC and Lean, rather than their contrasting.
Research question.
Can TOC be a part of Lean?
Methodology/Design.
The paper is based on the relevant literature review, in the frame of which the remarkable improvements of TOC and Lean integration are discovered and presented further as well. The paper consists of a theoretical part sourced from the literature, and analytical part with analysis, comparisons and arguments aiming to answer the stated research question. The future research area is discussed in the paper's conclusion.
Delimitation
The paper is focused on studies of Lean and TOC concepts in terms of their application into production. The reason of such delimitation is that both concepts started from shop floor targeting production processes.
Theoretical framework
Description of Lean concept
Lean thinking or the Toyota Production Systems (TPS), as it is sometimes called , was developed by "production genius" Taiichi Ohno, Japanese engineer at Toyota, who believed in
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Socratic method of developing managers through asking questions rather than giving answers or ready-made instructions [2]. The authors see the greatest opportunity for Lean in simplification and decentralization [2]. According to Melton (2005: 662), the system is based 'around the recognition that only a small fraction of the total time and effort to process a product added value to the end customer'. This approach was very different from the existing one in the West focused on large volume manufacturing of standardized products with minimal product changeovers [17]. Moreover, Lean contradicts the traditional accounting system because the latter reports on past performance and fails to reflect accurately the improvements made with Lean [2].
There are five well-known principles of Lean:
1. Identify value. This comes from marketing where established that customers buy results, not product. The purpose is to understand who the customer is and what the customer is ready to pay for [19].
2. Identify the value stream. This is all the way from raw material to end customer, the whole supply chain. "You are only as good as the weakest link; supply chain compete, not companies"[2].
3. Create a flow. To simplify the flow as much as possible, keep it moving, set a priority system of value adding activities over non value adding. Flow is dependent on strategy. Flow is a central concept of Lean [19].
4. Pull. It means quick response to the customers' rate of demand on both micro and macro levels of the company. For example, to have more staff during sales (micro) and have stock at an intermediate point in the supply chain to be more flexible providing good customer service. The customers should pull products through the chain [19].
5. Perfection. If it implements all four steps above, a company delivers a right product at right time, at right price. Keep the processes being perfect (Nave, 2002).
The Lean method is focused on the identification and elimination of waste in the company [5]. Waste is anything other than the minimum amount of equipment, materials, parts, space and worker's time, which are absolutely essential to add value to the product (Fujio Cho, former president of Toyota). Bicheno and Holweg, (2009) give an interesting explanation of waste in the form of a question: "Who is TIM WOOD?" The letters of the name stand for waste in differing areas: Transport, Inventory, Motion, Waiting, Overproduction, Over-Processing and Defects. According to the authors, the company should first try to avoid
System of thinking people
Goal, Policy, Strategy
FLOW: JIT QUALITY
S Whys
Ksnban Fall-Sale
Continuous Value Stream Mapping Respect for
Improve- SMED Lint Stop people
ment A3
Takt Time PDCA
Stability: SS, Visual Management, 7 Quality tools, Standard Operating Procedures (SOPs]
Challenge, Kaizen, Teamwork, Gemba
Figure 1. - The house of Lean. Adapted from [2]
waste and only later look to reduce it. Another focus of Lean is improving the flow of information and materials in the company[5].
Bicheno and Holweg, (2009) illustrate the Lean system as a house called "Lean Enterprise house" [2]. The figure below presents the combination of Lean philosophy with certain Lean techniques, providing the deeper view on what the Lean approach is about:
According to Bicheno and Holweg (2009) the philosophy of Lean starts with thinking people because only people can make a sustainable system. Further, continuous improvement and respect for people are two crucial factors for Toyota way due to the difficulty to stay away from inertia. The foundation emphasizes the importance of continuous change for better (Kaizen), ongoing challenge to react to changing environment, working together (Teamwork), and going to a shop floor and see yourself (Gemba). Value stream flow and quality control can be achieved by using different techniques of Lean [2]. Cudney and Elrod (2011) assert that the most commonly used Lean tools for eliminating waste and achieving flow are: value stream mapping (VSM), standard work, 5S housekeeping, single minute exchange of dies (SMED), and visual management. Bicheno and Holweg (2009) highlight the improvement cycle PDCA -Plan, Do, Check and Act as one of the essentials of Lean.
Finally, implementation of Lean tools and techniques helps to minimize wasted efforts and non-value adding activities through high level of collaboration and cooperation [16].
Description of TOC concept
TOC concept is a management philosophy, catching the attention of both academic and business communities. The concept of TOC is presented in "The Goal",
the book where the TOC's philosophy and techniques are given in Socratic and narrative format; it became mandatory reading in many management courses in the USA [18].
TOC focuses on system improvement where the system (chain) is interdependent links (processes) and the weakest link is a constraint. The performance of the entire chain is dependent on the performance of the weakest link[19].
Chou et al. (2012) provide the five focusing steps of TOC concept presented below. The steps focus on system improvement [19].
1. Identify the system's constraint or constraints. It is recommended to use VAT analysis, a constraint management procedure to determine the general flow of products or parts [7].
2. Decide how to exploit the constraint. The technique how to manage resources to maximize throughput is Drum-Buffer-Rope, where the Drum is the production's pace set by the constraint, the buffers protect over the uncertainty, and the rope is a communication process [7].
3. "Subordinate" all other resources to the constraint. Buffer management, which means a scheduled process regulating work in the shop. The priority system should be established, prioritizing the constraint over all resources and policies [7].
4. "Elevate" the constraint by, for example, having an additional machine or working more on the constraint [7].
5. Go back to the step 1, but do not allow inertia to cause a system constraint.[7]
Besides the five focusing steps, TOC has a tool called "Thinking Processes" (TP) aiming to make people faster identify the core of problems and find better solutions [15]. Lepore and Cohen, (2007) claim that TP could be the key to managing in changing
Theory LEAN TOC
Pulpóse Increase profit by adding value from customer's perspective Create flow and remove waste Increase profit by increasing throughput Manage flow through constraints and increase throughput
Steps 1 Identify value. 1. Identify constraint.
2. Identify value stream. 2. Exploit constraint.
3. Mow. 4. Pull. 3. Subordinate processes. 4. Elevate constraint.
5. Perfection 5. Repeat steps
b'ocus Flow Constraint
Measures Cost Lead time Throughput Inventory
Value added percentage Operating expenses
( haицг Eliminate waste and add value The weakest link of the system
Effects Improved quality Improved quality
New accounting system New accounting system
Main measure - flow Main measure - throughput
Less inventory Less inventory
Less variation Less variation
Figure 2. Similarity and distinctive features of TOC and Lean
and complex environment and a part of continuous learning.
Mabin and Balderstone (2003) explain TP that consists of five logic diagrams, look like a tree, and "a cloud". The authors claim that the trees are if/yes/then algorithms: current reality tree (CRT), future reality tree (FRT), prerequisite tree (PRT), transition tree (TT), then evaporating cloud (EC) and a set of logic rules, the Categories of Legitimate Reservation (CLR). Kasemset, (2011) assert that all the above mentioned tools deal with identifying undesirable effects (UDE) and deduce the causes of them, what to be done to improve the causes, and how the improvements could be implemented. Simply, TP can help a manager to answer the questions: "What to change?", "What to change to?", "How to cause the change to happen?" [11].
Mabin and Davies (2008) claim that using TP tools via cause-and-effect thinking following strict logic rules, combining with personal intuition and knowledge, could be applied to any kind of problems, tackle them with high efficiency.
Finally, TOC is in conflict with the traditional accounting system because TOC perceives the system as a whole, while the traditional accounting system asserts that every single product must be profitable [12]. The literature on TOC has however been criticized, emphasizing future research [8].
Literature review on TOC and Lean comparison and integration
There are some studies on TOC where the scholars compare or integrate TOC with Lean techniques. For example, Sale and Inman (2003) analyze the performance of various respondents, using TOC, traditional manufacturing, JIT and JIT/TOC. Watson and
Patti (2008) also compare JIT and TOC between the simulation of certain tools of both concepts, Kanban and DBR. Gupta and Snyder (2009) review the literature on TOC, MRP and JIT, comparing the mentioned concepts. Gupta et al., (2003) integrates TOC and ABM (Activity Based Management) approaches. Gupta and Snyder (2009) refer to Valmont Industries reports about successful integration of TOC's software (OPT) into existing MRP. Alsmadi (2014) integrates ABC (Activity Based Costing) and TOC enhancing decision-making in a Lean concept and providing managers with more accurate information on pricing, production etc. Huang et al. (2014) also apply integrated TOC and ABC into information system of a company. Kasemset (2011) reviews literature on TOC and quality improvement with a combination of TOC, Lean and Six Sigma. Librelato et al., (2014) integrate Value Stream Mapping and TP of TOC. Moreover, there is a book issued recently by Srinivasan (2012) on how to build Lean supply chain with TOC (Selviaridis, 2014). All the authors stress the significant improvements in the area of their study due to TOC application.
In addition, Rattner (2002) writes about the possibility to integrate TOC in Lean between 2nd and 3d steps of Lean.
Finally, according to Bicheno and Holweg, (2009) accounting, design and supply chain practices have been added recently to Lean. Other theories like Six Sigma (a technique to reduce variation) became now a part of Lean known as Lean Six Sigma [2].
Analysis on integration TOC and Lean.
The similarity and distinctive features of TOC and Lean based on the literature review are identified, summarized and presented below.
As seen from the table above, the two concepts have much in common but focus on different parameters: flow and constraint. Both philosophies are based on strict logic and Socratic methods, according to Naor et al. (2013) and Bicheno and Holweg, (2009), targeting the same - to improve flow and throughput. Based on description of "mechanism" of TOC and Lean in the theoretical framework, it is obvious that the approaches of both concepts are different but fully compatible. For example, TOC deals with bottlenecks and shared resources, scheduling around them, while Lean tries to avoid any bottlenecks, creating clear value stream with no shared resources. TOC is able to identify where to start with the improvements faster because the constraints, according to Goldratt and Cox (1992), for example in the shop floor, are visible due to huge inventory in front. However, Lean's mapping tools help to understand the whole system clearer. Therefore, Lean and TOC do not contradict, but supplement each other.
Lepore and Cohen, (2007) and Bicheno and Holweg, (2009) claim that both philosophies emphasize on contradiction to the traditional accounting system based on a difference in assumption of the system, as traditional accountants believe that improving a part as a separate thing, the whole system improves. By contrast, Lean and TOC perceive the system as a whole, value stream view in Lean and throughput system in TOC.
According to Bicheno and Holweg (2009), PDCA (Plan, Do, Check and Act) is one of the essentials of Lean. Five focusing steps of TOC are very similar with PDCA of LEAN, but more focused. Both approaches aim to identify issues, deal with identified issues, learn from them and repeat the cycle again and again; the goal being to create a perfect flow and value for the customers at the end. In addition, five focusing steps of TOC or its improvement cycle are in line with continuous change for better of Kaizen.
Furthermore, one of the fundamental principles of Lean is the emphasis on solving the problems' root causes [5]. Thus, TP of TOC and 5Whys technique of Lean are different approaches applied for achieving a similar purpose.
Lean today is more than a theory; it is a philosophy and system that is in ongoing interaction with the environment. Lean is developing continuously in terms of employment, attention to quality, just-in-time methods [2]. Extension of Lean to Six Sigma implies a certain degree of flexibility of Lean even though traditional Lean tends to ignore variation.
Due to such flexibility of Lean philosophy
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and capability to embrace other theories thus enhancing its own power, the techniques of Lean and TOC can also be incorporated to increase the performance of the company. For example, Sale and Inman (2003), Gupta and Snyder (2009), Gupta et al., (2003), Alsmadi (2014), Huang et al., (2014), Kasemset (2011) and Selviaridis (2014) write about considerable improvements in companies performance due to application of TOC or its combination with various techniques of Lean. Moreover, the integration of TOC between the 2nd and 3d steps of Lean mentioned by Rattner (2002), improves the value stream due to constraints elimination. In this case, TOC would identify constraints providing improvements to value stream, and TOC's performance measures would support Lean.
The literature review on TOC and Lean discloses that the scholars initially tried to compare TOC with Lean's techniques aiming to identify distinguish features of TOC and find the best applied concept [7, 9, 19, 22, 25,]. The recent studies, in turn, show the integration of TOC with Lean's techniques [1, 7, 10, 11, 23]. Consequently, the academic community understands and is researching the potential of integrating the two philosophies.
Finally, based on the similarities identified in the nature of TOC and Lean as well as their capability to be incorporated, it is possible to claim that TOC can be a part of Lean. Moreover, the integration of TOC and Lean can lead companies to higher level of performance.
Conclusion
Lean is a global philosophy employing different tools, applied and discussed extensively in business and academic communities. TOC, in turn, with its techniques can be integrated into Lean, enhancing some aspects of the performance of companies already using Lean. In the current rapidly changing environment, internal and external constraints are inevitable; that is why TOC with its focus on constraints can be a useful technique for application with Lean.
The paper addressed the issue on incorporating TOC and Lean. The methodology of Lean and TOC was described based on relative literature review. In the analysis part, Lean and TOC were compared and analyzed aiming to reveal similarities rather than contradiction of these two philosophies. Data gathered through the comparison and literature review showed the possibility to incorporate TOC into Lean proved that TOC could be a part of Lean supporting and enhancing the latter and improving the companies' performance.
However, the studies presented in the paper were focused on Lean and TOC in
terms of production processes (Lean is also known as Toyota Production System and TOC itself started from the factory floor). Therefore, there exist opportunities for future research on TOC, TOC's TP and Lean techniques in terms of project management, supply chain management, enterprise resource management.
Lean and the Theory of Constraints. Can the Theory of Constraints be a part of Lean? Mukhina M.V.
Russian Gas Turbines LLC Management literature provides various techniques on how to improve companies' performance while managers would like to have one universal tool, which gives all the required solutions. However, the main pending issue remains -what method is superior amongst others and what method to choose. This paper discusses Lean and the Theory of Constraints (TOC), their similarity and distinction, and how they can be complementary to each other. The research is based on academic literature review, in which Lean seems a theorem not to be evidenced, while TOC sometimes is a doubtable theory with lack of confirmed results. The analytical part presents the way of TOC integration into Lean and, moreover, the arguments that TOC is inherently a part of Lean. The paper is concluded with future possible research area on the subject matter. Key words: TOC, Lean, Theory of Constraints, JIT, concept, value chain, production
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