The meaning of "lean"

Michel Baudin, 8/11/97

Since, in "The Machine That Changed the World," Womack & Jones coined the term "lean production" as a synonym of "JIT," it has caught on and given the earlier label an obsolete connotation. Consultants who still talk about JIT are dismissed as stale moustache-petes peddling yesterday's panacea, while those who say the exact same things but call it "lean" get attention. As interest in JIT/lean production grows, this vocabulary engineering is also accompanied by scope creep: what started out with a focus on the factory expands to cover product design, office work, distribution, and services. And new terms follow: you now hear about "lean manufacturing," "lean management," "lean enterprise" and "lean thinking." It is safe to say that "lean life" is not far behind.

This expansion also involves dilution. By being generalized beyond anything Ohno could have the leisure to think about, his specific recommendations about on how to set up production lines or use people get watered down to little more than exhortations to be good. In their book "Lean Thinking," Womack & Jones came up with five principles as a thumbnail summary of "lean," based on such notions as a "value stream," that are not obvious to manufacturing people. Our job is to fix factories, and we need to be down to earth. What exists that can be called "lean" anything is about the production of goods, not airlines or insurance. Lean production is a bag of tricks invented by Ohno and people around him to make cars and car parts, and we need to adapt it to making soap, integrated circuits, or airplanes. For this purpose, it is useful to extract some guiding principles but we must express them in simple words with a clear and concrete meaning that shop floor people can relate to.

Following are a few points that we keep having to explain over and over again, which tells us that they are neither obvious nor trivial:

  1. People are the main driver of productivity. In some industries, such as semiconductors, many executives refuse to consider that the way operators are used on the shop floor matters. To them, people are cheap compared to equipment, and they are ready to use more than necessary as insurance that the equipment will keep running. The fact is that even expensive equipment is easier to replace than the people who know how to program, run, and troubleshoot it. A competitive advantage does not come from the possession of equipment but from excellence in using it, and this requires taking advantage of everything people have to offer, both muscles and brains. This requires them to feel trusted, respected, and challenged, which does not happen if they are treated like a disposable commodity and underutilized. The right pace and variety of work, engaging the individual without burning him or her out, impacts both productivity and quality.
  2. The key to profits is on the shop floor. Again, many executives will disagree with this statement, on the grounds, for example, that getting a product to market first is more important than making it cheaply. Their mistake is to assume that it doesn't matter how the shop floor works when your objective is fast time to market for new products. As much care is needed to set up a factory that will whisk through new products effectively as to reduce the production costs of a mature product. Waste does not usually take the form of big lumps that can be trimmed away, but rather is “marbled” through the manufacturing process, and can only be eliminated by paying attention to what happens at every step. When Toyota executives visit suppliers, they go to the shop floor and observe how operators and machines are working; to them, attention to shop floor detail is a strategy.
  3. All manufacturing is repetitive. This too is controversial. "We make to order and every unit is custom-engineered," we hear. But when we dig into the process we find that all units are identical until the last operation and customized only then. In all manufacturing operations, there is some form of repetitiveness which may not be obvious but must be sought out in process design. Being flexible, or agile, means being able to make whatever customers want, but it does not require the manufacturer to be actually able to make what anybody might order. It is sufficient to make what customers actually do order. Most of them order from a small range of options, that you produce repetitively on lines dedicated by product or product family, and for the few who actually order specials, you set up a separate, small-scale job-shop. Taking advantage of the structure of the actual demand enables you appear infinitely flexible without incurring the cost of being so.
  4. The work must flow through the shop. The equipment and layout must be designed around the flow of work through the shop and not the other way around, to eliminate the “hurry-and-wait” pattern for materials and the“stop-and-go” pattern for equipment and people. You must match actual production rates at each operation to the takt time, and move work between operations one piece at a time or in small lots with frequent setups. Transfers of parts from suppliers or between lines within the plant must be on a “pull” and not a “push” basis.
  5. Improve, don’t optimize. Engineers are trained in school to seek optimal solutions. The optimum, however, only exists within a mathematical model, and once you have reached it, by definition, no further improvement is possible. On the shop floor, there is no optimum and no limit. You can and should always improve operations, right up until the plant closes. In 1996, after 40 years of implementing JIT/lean production, Toyota redesigned its assembly lines in Japan, and improved operator productivity by 10%!

Are these statements all there is to it? Probably not. They are just our best shot so far.