| This art: Introduction Lean manufacturing & thinking (1) |
Lean: The value adding organization |
| ^ More articles about Lean can be found using the yellow dropdown menu above left. This is the opening, introductory article. | ||
| Introduction
lean manufacturing Lean manufacturing is a method for improving industrial processes which, just as the Theory of Constraints (TOC) and Quick Response Manufacturing (QRM), was developed using a logistics management line of approach. Lean concentrates on minimizing waste. A process flow diagram (value stream mapping) is used to identify which industry processes add value to the products or services provided by your company, and which don’t. The goal is to make the “value stream” as large as possible. Often it turns out to be smart to let materials, documents or semi-manufactured items flow through the company in as steady a stream as possible (flow manufacturing), at a speed dictated by market demand (pull) Lean manufacturing originated in Japan, where it was first applied by Toyota. Later, Lean was further developed and promoted by researchers of the Massachusetts Institute of Technology (MIT) in the US; see the lean cycle of Womack & Jones. The value adding organization Lean manufacturing was originally only applied by companies and institutions with flow-driven production and with many consecutive steps . Many production steps means there are plenty of points where wastage can be minimized, especially if the company is part of a supply chain! Examples of these early Lean adopters can be found in the automotive, metal and electronics sectors. Since its early days, Lean evolved into a process management method that is generally applicable – even outside production. For example, Value Stream Mapping and lean management is useful in almost any organization, including hospitals. Lean can also be applied in the design phase of products, as Philips does when they speak about “Lean Product Innovation”. |
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By Dr Jaap van Ede, business-journalist, founder business-improvement.eu
According to Aerdts, lean manufacturing used to have quite a negative connotation about ten years ago.  ^ The design of the Lean assembly line at Eaton makes sure that there is room for only one intermediate piece of stock. The result is a one-piece flow. (Photo: Eaton Automotive, Montfoort) Japan Curiously, the name ‘lean manufacturing’ was not introduced by the Japanese, but by two Americans, James P. Womack and Daniel Jones from the Massachusetts Institute of Technology. Aerdts says, 'The same applies to just-in-time, one of many methods that complement Lean. That expression was also introduced by Western researchers, who were describing Japanese production methods.' The first version of this article was published in 2005 in the Dutch specialist journal PT Industrial Management. The article is updated regularly on this website.
Value stream mapping In lean manufacturing only those processes for which a client is willing to pay are regarded as profitable. Any other activities are essentially waste, and should be restricted as much as possible. ' Value stream mapping is the most important tool to achieve this', Aerdts explains. 'You map your company processes in a flow diagram, using arrows and blocks. At each point you indicate how much of your valuable time is actually being spent on the product, and how much time is wasted on other aspects, such as waiting and transport. If you do this for an average company then it’s quite normal to find that less than 1% of the time is spent on adding value! The goal of lean manufacturing is to raise that percentage. You can do this, for example, by combining production steps at one workstation, or by decreasing the stock between workstations.' This idea is not completely new. Long ago Henry Ford (1863-1947), the father of the modern assembly lines, already suggested that machines should be placed as close to each other as possible, so that no stocks could fit between them. Aerdts agrees. 'We’re constantly re-examining old production concepts. I still learn something new from that every day. Think of methods that were invented in the 20th century, such as demand-driven production and flow manufacturing. These concepts are now being used to minimize sources of waste.' Once a companies starts to apply lean manufacturing, they tend to stick that label on any other process improvement method they might use. This broad use of the term “Lean” can lead to confusion. Lean cycle in five steps
Womack & Jones distinguish the following five steps in the lean improvement cycle:
Many processing steps Broad application Lean Manufacturing: the jargon
The goal of Lean manufacturing is to make a company’s value stream as big as possible. Seven categories of waste should therefore be reduced as far as possible: overproduction, inventory, manufacturing faults, manufacturing disruptions, waiting times, transport and unnecessary movement. The last category includes looking for materials or tools in the workplace. The above mentioned sources of waste can be identified by applying Value Stream Mapping. After that, there are many tools which can be used to reduce these wasteful activities. Many of those tools are based on a (sometimes much older) production concepts, which were developed in the 20th century.
The concepts above are typical in lean manufacturing but can also be applied in combination with other process improvement methods. Many other concepts, less exclusively related to Lean, can also be used to reduce waste. Several popular methods are:
Case study: Eaton Automotive
Eaton Automotive in Montfoort, the Netherlands, produces mirror controls for cars. 'More then ten years ago, we were still a family business,’ says Onno Oenema, Assembly Engineering Manager. 'Straight after the takeover by the American company Eaton, in 1995, we became firmly committed to lean manufacturing. Soon after that we attended courses in value stream mapping. We didn’t need help from an external consultancy firm, because support came and still comes from America. Eaton is a big company, comparable to General Electric. We have our own in-house knowledge center for lean manufacturing and quality control.' Oenema thinks that Americans are very good at introducing process improvement methods. 'They simply enforce change,' he says. 'Their corporate culture permits that. It’s far more hierarchical than what we Northern Europeans are used to. That’s why the EU is lagging behind when it comes to Lean. But now there is growing interest in Lean thinking. The Dutch Association of Suppliers, the NEVAT, has recently started to organize Lean symposia.' After lean manufacturing was introduced in his factory, Oenema quickly saw significant changes. 'The most obvious waste eliminated was our inventory of intermediate parts. We make about a hundred types of mirror controls. These all contain about twenty synthetic parts, that we have to spray paint and assemble. Before Lean, we had a storage rack, fifty meters long and four meters high, filled right up with stock. Sometimes we had enough inventory for a whole week of production! Now, our inventory per article never exceeds the amount which is sufficient for four hours of production. So we just don’t need that huge storage rack anymore.' The freed space came in handy during a revision of the factory lay-out. 'Once we’d mapped our value stream and our various production processes, it became clear that our work floor organization was illogical', Oenema continues. 'Now we’ve aligned our machines in flow. Parts and materials enter the factory at one end, and the finished products exit at the other end.'
Eaton makes a distinction between takt time and machine time. 'The takt time is determined by customer demand,' Oenema explains. 'As a rule, we never produce faster than the speed at which the customer’s orders arrive. Our machine cycle time must equal the takt time at least, but should preferably be faster. If our workers have finished a particular operation, then they can start doing something else.' Information on the machine’s performance is visible on boards besides each machine. A multidisciplinary team – with engineers, operators and maintenance technicians – implements improvements autonomously and continuously. 'This approach has led to considerably fewer machine breakdowns and less product rejection.' The machine performance information is crucial to identify and address the causes of the most frequently ocurring breakdowns. 'That’s why we invested in software that automatically updates the data.' Since the work flow is demand-driven, batch sizes are smaller and change-overs occur more frequently. This has had most impact on the operation of the spray painting machines. Oenema: 'Because we need to swap the dies now much faster than before, the application of SMED is very important to us.' Lean manufacturing doesn’t need to be restricted to the factory floor. Currently Eaton is looking for potential improvements in assembly equipment design. This department designs all the machines the company uses to assemble the mirror controls. 'We first examined the design process. Value stream mapping has thrown a clear light on quite a lot of non-value added time, specifically waiting times. That’s interesting, as everyone in the design department always seems to be extremely busy! The root cause turned out to be missing information, when a design is passed on from one designer to another.' The aim is to re-organize the design steps in as logical a sequence as possible. 'We’ve devised a standard protocol, with the aim to implement lean manufacturing concepts at every phase of the machine design process, such as Poka Yoke or SMED-principles', Oenema says. 'This early management is already having effect. We’ve designed a manual assembly line for a sister-company in Ireland. While doing that, we made sure there is only space between the machines to store one intermediate part' |
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© C.J. van Ede 2006-2010 (NL/Europe/Worldwide) |
Update: 25-10-2011 | |
