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It has been suggested that Lean Systems be merged into this article or section. (Discuss) |
Lean manufacturing is the production of goods using less of everything compared to traditional mass production: less waste, human effort, manufacturing space, investment in tools, inventory, and engineering time to develop a new product. Lean manufacturing is a generic process management philosophy derived mostly from the War Manpower Commission which led to the Toyota Production System (TPS)Womack, James P., Jones, Daniel T., and Roos, Daniel (1991), The Machine That Changed the World and also from other sources. It is renowned for its focus on reduction of the original Toyota \'seven wastes\' in order to improve overall customer value but has some key new perspectives on how to do this. Lean is often linked with Six Sigma because of that methodology\'s emphasis on reduction of process variation (or its converse smoothness) and Toyota\'s combined usage (with the TPS). Toyota\'s steady growth from a small player to the most valuable and the biggest car company in the world has focused attention upon how it has achieved this.
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For many, Lean is the set of TPS \'tools\' that assist in the identification and steady elimination of waste (muda), the improvement of quality, and production time and cost reduction. The Japanese terms from Toyota are quite strongly represented in "Lean". To solve the problem of waste, Lean Manufacturing has several \'tools\' at its disposal. These include continuous process improvement (kaizen), the "5 Whys" and mistake-proofing (poka-yoke). In this way it can be seen as taking a very similar approach to other improvement methodologies.
There is a second approach to Lean Manufacturing, which is promoted by Toyota, in which the focus is upon improving the \'flow\' or smoothness of work (thereby steadily eliminating mura, unevenness) through the system and not upon \'waste reduction\' per se. Techniques to improve flow include production levelling, "pull" production (by means of kanban) and the Heijunka box. This is a fundamentally different approach to most improvement methodologies which may partially account for its lack of popularity.
The difference between these two approaches is not the goal but the prime approach to achieving it. The implementation of smooth flow exposes quality problems which already existed and thus waste reduction naturally happens as a consequence. The advantage claimed for this approach is that it naturally takes a system-wide perspective whereas a \'waste\' focus has this perspective, sometimes wrongly, assumed. Some Toyota staff have expressed some surprise at the \'tool\' based approach as they see the tools as work-arounds made necessary where flow could not be fully implemented and not as aims in themselves.
Both Lean and TPS can be seen as a loosely connected set of potentially competing principles whose goal is cost reduction by the elimination of waste.Toyota Production System, Taichi Ohno (1988), Productivity Press, p 8, ISBN 0-915299-14-3 These principles include: Pull processing, Perfect first-time quality, Waste minimization, Continuous improvement, Flexibility, Building and maintaining a long term relationship with suppliers, Autonomation, Load levelling and Production flow and Visual control. The disconnected nature of some of these principles perhaps springs from the fact that the TPS has grown pragmatically since 1948 as it responded to the problems it saw within its own production facilities. Thus what one sees today is the result of a \'need\' driven learning to improve where each step has built on previous ideas and not something based upon a theoretical framework. Toyota\'s view is that the methodology is not the tools but the method of application of muda, mura, muri to expose problems systematically and to use the tools where the ideal cannot be achieved. Thus the \'tools\' are, in their view, \'workarounds\' adapted to different situations which explains any apparent incoherence of the \'principles\' above.
The TPS has two pillar concepts: JIT (flow) and autonomation (smart automation).Taichi Ohno (1988), p 4 Adherents of the Toyota approach would say that the smooth \'flow\'ing delivery of \'value\' achieves all these improvements as a side-effect. If production \'flows\' perfectly then there is no inventory, if customer valued features are the only ones produced then product design is simplified and effort is only expended on features the customer values. The other of the two TPS pillars is the very human aspect of \'autonomation\' whereby automation is achieved with a human touch.Taichi Ohno (1988), p 6 This aims to give the machines enough \'intelligence\' to recognise when they are working abnormally and flag this for human attention. Thus humans do not have to monitor normal production and only have to focus on abnormal, or fault, conditions. A reduction in human workload that is probably much desired by all involved since it removes much routine and repetitive activity that humans often do not enjoy and where they are therefore not at their most effective.
Lean implementation is therefore focused on getting the right things, to the right place, at the right time, in the right quantity to achieve perfect work flow while minimizing waste and being flexible and able to change. These concepts of flexibility and change are principally required to allow production leveling, using tools like SMED, but have their analogues in other processes such as R&D. The flexibility and ability to change are not open-ended, and therefore often not expensive capability requirements. More importantly, all of these concepts have to be understood, appreciated, and embraced by the actual employees who build the products and therefore own the processes that deliver the value. The cultural and managerial aspects of Lean are just as, and possibly more, important than the actual tools or methodologies of production itself. There are many examples of Lean tool implementation without sustained benefit and these are often blamed on weak understanding of Lean in the organization.
Lean aims to make the work simple enough to understand, to do and to manage. To achieve these three at once there is a belief held by some that Toyota\'s mentoring process (loosely called Senpai and Kohai relationship), so strongly supported in Japan, is one of the best ways to foster Lean Thinking up and down the organizational structure. This is the process undertaken by Toyota as it helps its suppliers to improve their own production. The closest equivalent to Toyota\'s mentoring process is the concept of Lean Sensei, which encourages companies, organizations, and teams to seek out outside, third-party "Sensei" that can provide unbiased advice and coaching, (see Womack et al, Lean Thinking, 1998).
Most of the basic goals of lean manufacturing are common sense and documented examples can be seen back to at least Benjamin Franklin. Poor Richard\'s Almanack says of wasted time, "He that idly loses 5s. [shillings] worth of time, loses 5s., and might as prudently throw 5s. into the river." He added that avoiding unnecessary costs could be more profitable than increasing sales: "A penny saved is two pence clear. A pin a-day is a groat a-year. Save and have."
Again Franklin\'s The Way to Wealth says the following about carrying unnecessary inventory. "You call them goods; but, if you do not take care, they will prove evils to some of you. You expect they will be sold cheap, and, perhaps, they may [be bought] for less than they cost; but, if you have no occasion for them, they must be dear to you. Remember what Poor Richard says, \'Buy what thou hast no need of, and ere long thou shalt sell thy necessaries.\' In another place he says, \'Many have been ruined by buying good penny worths\'." Henry Ford cited Franklin as a major influence on his own business practices, which included Just-in-time manufacturing.
The concept of waste being built into jobs and then taken for granted was noticed by motion efficiency expert Frank Gilbreth, who saw that masons bent over to pick up bricks from the ground. The bricklayer was therefore lowering and raising his entire upper body to get a 5 pound (2.3 kg) brick but this inefficiency had been built into the job through long practice. Introduction of a non-stooping scaffold, which delivered the bricks at waist level, allowed masons to work about three times as quickly, and with less effort.
Frederick Winslow Taylor, the father of scientific management, introduced what are now called standardization and best practice deployment: "And whenever a workman proposes an improvement, it should be the policy of the management to make a careful analysis of the new method, and if necessary conduct a series of experiments to determine accurately the relative merit of the new suggestion and of the old standard. And whenever the new method is found to be markedly superior to the old, it should be adopted as the standard for the whole establishment" (Principles of Scientific Management, 1911).
Taylor also warned explicitly against cutting piece rates (or, by implication, cutting wages or discharging workers) when efficiency improvements reduce the need for raw labor: "…after a workman has had the price per piece of the work he is doing lowered two or three times as a result of his having worked harder and increased his output, he is likely entirely to lose sight of his employer\'s side of the case and become imbued with a grim determination to have no more cuts if soldiering [marking time, just doing what he is told] can prevent it." This is now a foundation of lean manufacturing, because it is obvious that workers will not drive improvements they think will put them out of work. Shigeo Shingo, the best-known exponent of single-minute exchange of die (SMED) and error-proofing or poka-yoke, cites Principles of Scientific Management as his inspiration (Andrew Dillon, translator, 1987. The Sayings of Shigeo Shingo: Key Strategies for Plant Improvement).
American industrialists recognized the threat of cheap offshore labor to American workers during the 1910s, and explicitly stated the goal of what is now called lean manufacturing as a countermeasure. Henry Towne, past President of the American Society of Mechanical Engineers, wrote in the Foreword to Frederick Winslow Taylor\'s Shop Management (1911), "We are justly proud of the high wage rates which prevail throughout our country, and jealous of any interference with them by the products of the cheaper labor of other countries. To maintain this condition, to strengthen our control of home markets, and, above all, to broaden our opportunities in foreign markets where we must compete with the products of other industrial nations, we should welcome and encourage every influence tending to increase the efficiency of our productive processes."
Henry Ford continued this focus on waste while developing his mass assembly manufacturing system:
Ford\'s success has startled the country, almost the world, financially, industrially, mechanically. It exhibits in higher degree than most persons would have thought possible the seemingly contradictory requirements of true efficiency, which are: constant increase of quality, great increase of pay to the workers, repeated reduction in cost to the consumer. And with these appears, as at once cause and effect, an absolutely incredible enlargement of output reaching something like one hundredfold in less than ten years, and an enormous profit to the manufacturer.(Charles Buxton Going, preface to Arnold and Faurote, Ford Methods and the Ford Shops (1915))
Ford (1922, My Life and Work) provided a single-paragraph description that encompasses the entire concept of waste:
I believe that the average farmer puts to a really useful purpose only about 5%. of the energy he expends.... Not only is everything done by hand, but seldom is a thought given to a logical arrangement. A farmer doing his chores will walk up and down a rickety ladder a dozen times. He will carry water for years instead of putting in a few lengths of pipe. His whole idea, when there is extra work to do, is to hire extra men. He thinks of putting money into improvements as an expense.... It is waste motion— waste effort— that makes farm prices high and profits low.
Poor arrangement of the workplace--a major focus of the modern kaizen--and doing a job inefficiently out of habit-- are major forms of waste even in modern workplaces.
Ford also pointed out how easy it was to overlook material waste. As described by Harry Bennett1951, Ford: We Never Called Him Henry:
One day when Mr. Ford and I were together he spotted some rust in the slag that ballasted the right of way of the D. T. & I [railroad]. This slag had been dumped there from our own furnaces. \'You know,\' Mr. Ford said to me, \'there\'s iron in that slag. You make the crane crews who put it out there sort it over, and take it back to the plant.\'
In other words, Ford saw the rust and realized that the steel plant was not recovering all of the iron.
Design for Manufacture (DFM) also is a Ford concept. Per My Life and Work
Start with an article that suits and then study to find some way of eliminating the entirely useless parts. This applies to everything— a shoe, a dress, a house, a piece of machinery, a railroad, a steamship, an airplane. As we cut out useless parts and simplify necessary ones, we also cut down the cost of making. ...But also it is to be remembered that all the parts are designed so that they can be most easily made.
The same reference describes just in time manufacturing very explicitly.
While Ford is renowned for his production line it is often not recognized how much effort he put into removing the \'fitters\' work in order to make the production line possible. Until Ford a car\'s components always had to be \'fitted\' or reshaped by a skilled engineer at the point of use so that they would connect properly. By enforcing very strict specification and quality criteria on component manufacture he eliminated this work almost entirely, this reduced manufacturing effort by between 60-90%.David A. Hounshell, From the American System to Mass Production, 1800-1932 (John Hopkins University Press, 1984), 248 and subsequent However Ford\'s mass production system failed to incorporate the notion of "Pull" and thus often suffered from over production.
Toyota\'s development of ideas that later became Lean may have started at the turn of the 20th century with Sakichi Toyoda in their textile business with looms that stopped themselves when a thread broke, this became the seed of "Autonomation" and "Jidoka". Toyota\'s journey with JIT may have started back in 1934 when it moved from textiles to produce its first car. Kiichiro Toyoda, founder of Toyota Motor Corp., directed the engine casting work and discovered many problems in their manufacture. He decided he must stop the repairing of poor quality by intense study of each stage of the process. In 1936, when Toyota won its first truck contract with the Japanese government, his processes hit new problems and he developed the "Kaizen" improvement teams.
Levels of demand in the Post War economy of Japan were low and the focus of mass production on lowest cost per item via economies of scale therefore had little application. Having visited and seen supermarkets in the US Taiichi Ohno recognised the scheduling of work should not be driven by sales or production targets but by actual sales. Given the financial situation during this period over-production had to be avoided and thus the notion of Pull (build to order rather than target driven Push) came to underpin production scheduling.
It was with Taiichi Ohno at Toyota that these themes came together. He built on the already existing internal schools of thought and spread their breadth and use into what has now become the Toyota Production System (TPS). It is principally from the TPS, but now including many other sources, that Lean production is developing. Norman Bodek wrote the following in his foreword to a reprint of Ford\'s (1926) Today and Tomorrow: "I was first introduced to the concepts of just-in-time (JIT) and the Toyota production system in 1980. Subsequently I had the opportunity to witness its actual application at Toyota on one of our numerous Japanese study missions. There I met Mr. Taiichi Ohno, the system\'s creator. When bombarded with questions from our group on what inspired his thinking, he just laughed and said he learned it all from Henry Ford\'s book." It is the scale, rigour and continuous learning aspects of the TPS which have made it a core of Lean.
While the elimination of waste seem like a simple and clear subject it is noticeable that waste is often very conservatively identified. This then hugely reduces the potential of such an aim. The elimination of waste is the goal of Lean, and Toyota defined three types of waste: muda or nonvalue-added work, muri or overburden and mura or unevenness.
To link these three concepts is straightforward. Firstly, Muri focuses on the preparation and planning of the process, or what work can be avoided proactively by design. Next, Mura then focuses on implementation and the elimination of fluctuation at the scheduling or operations level, such as quality and volume. The third — Muda — is discovered after the process is in place and is dealt with reactively. It is seen through variation in output. It is the role of management to examine the Muda, or waste, in the processes and eliminate the deeper causes by considering the connections to the Muri and Mura of the system. The Muda – waste – and Mura – inconsistencies – must be fed back to the Muri, or planning, stage for the next project.
A typical example of the interplay of these wastes is the corporate behaviour of "making the numbers" as the end of a reporting period approaches. Demand is raised, increasing (mura), when the "numbers" are low which causes production to try to squeeze extra capacity from the process which causes routines and standards to be modified or stretched. This stretch and improvisation leads to muri style waste which leads to downtime, mistakes and backflows and waiting, thus the muda of waiting, correction and movement.
Observers who have toured Toyota plants have described their aim as \'learning to see\' these wastes in order to carry back a new vision of \'ideal\' to their parent companies.
The original seven muda \'deadly wastes\' are:
Some of these definitions may seem rather \'idealist\' but this tough definition is seen as important. The clear identification of \'non-value adding work\', as distinct from waste or work, is critical to identifying the assumptions behind the current work process and to challenging them in due course. In the words of Taiichi Ohno "eliminate muda, mura, muri completely".Toyota Vision and Philosophy,[1] Breakthroughs in SMED and other process changing techniques rely upon clear identification of where untapped opportunities may lie if the processing assumptions are challenged.
With a tools based approach
| With a muri or flow based approach (as used in the TPS with suppliersThe Gold Mine, F & M Ballé, The Lean Enterprise Institute, 2005, p196).
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Whilst Lean is seen by many as a generalization of the Toyota Production System into other industries and contexts there are some acknowledged differences that seem to have developed in implementation.
Lean, as a concept or brand, has captured the imagination of many in different spheres of activity. Examples of these from many sectors are listed below.
Lean principles have been successfully applied to call center services to improve live agent call handling. By combining Agent-assisted Voice Solutions and Lean\'s waste reduction practices, a company reduced handle time, reduced between agent variablity, reduced accent bariers, and attained near perfect process adherence. Dennis Adsit (2007) Cutting Edge Methods Target Real Call Center Waste, isixsigma.com, http://www.isixsigma.com/library/content/c070611a.asp
A study conducted on behalf of the Scottish Executive, by Warwick University, in 2005/06 found that Lean methods were applicable to the public sector, but that most results had been achieved using a much more restricted range of techniques than Lean provides. [2]
The challenge in moving Lean to services is the lack of widely available reference implementations to allow people to see how it can work and the impact it does have. This makes it more difficult to build the level of belief seen as necessary for strong implementation. It is also the case that the manufacturing examples of \'techniques\' or \'tools\' need to be \'translated\' into a service context which has not yet received the level of work or publicity that would give starting points for implementors. The upshot of this is that each implementation often \'feels its way\' along as must the early industrial engineers of Toyota. This places huge importance upon sponsorship to encourage and protect these experimental developments.
Just-in-time (JIT) is the most used and recognized lean manufacturing technique. For many years just-in-time has been misused or misunderstood for many American manufacturing companies. According to the book, "Running Today\'s Factory", some people think that JIT means Just Implement Techniques, in other words, use "best practices". The correct definition of just-in-time is having the right part at the right place in the right amount at the right time. This technique shortens cycle times, decreases the amount of inventory that a company carries, leads to low work-in-process (WIP), and creates a flexible atmosphere for the type or amount of product that a company would like to run and most of all streamlines work flow through a manufacturing facility. Davis, Dale; Standard, Charles (1999). Running Today\'s Factory, A Proven Strategy for Lean Manufacturing. Hanser Gardner Publications, 293. ISBN 1-56990-257-7.
Those areas below are linked to this subject:
Closely related methodologiesTerminology |
Areas of implementation outside ProductionTQM Other |
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