The bare necessities of lean: 10 things your lean guru may not tell you about making just-in-time work.

The current intense interest in lean manufacturing represents a validation of industrial engineering principles and practice. However, as with many popular management movements, there is a lot of misinformation and confusion regarding the application of lean principles. As the lean manufacturing message spreads, it becomes diluted and altered, causing lean implementations to fall. The result of effective lean implementation is to increase productivity, and productivity equals wealth. There are 10 important ideas and features that in-time systems require to achieve this result.

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1 Lean manufacturing is a philosophy.

Due to the prodigious amount of information available about lean tools and techniques, many people don't realize that lean manufacturing is a philosophy--the philosophy of avoiding waste in the manufacturing system. Taiichi Ohno made that philosophical message clear in his book Toyota Production System, in which he stated that the preliminary step toward applying that system is identifying waste completely. He then described the seven types of waste in a manufacturing system: overproduction, time on hand (waiting), transportation, processing, stock on hand (inventory), movement, and making defective products.

Industrial engineers are trained to develop systems that avoid waste, and Ohno acknowledges the contributions of industrial engineering to his development of the Toyota Production System: "IE is a system and the Toyota production system may be regarded as Toyota-styled IE," he writes. In addition to the issue of eliminating waste, Ohno stressed the idea of continuous improvement, believing that IEs study systematic approaches to improvement.

2 Reducing process variation is more important than reducing cycle time.

W. Edwards Deming once said, "If I had to reduce my message for management to just a few words, I'd say it all had to do with reducing variation." Stable processes and standardized work are needed before other lean tools will work well. In fact, a simple example using queuing theory shows that reducing process variation is more important than cycle time in improving throughput. However, while reducing process variation is usually mentioned, it is not often discussed in much detail in the popular lean literature for two reasons: First, processes vary from industry to industry, and in order to improve a process you must be knowledgeable about the process physics and chemistry. Second, for labor-intensive processes, you should be trained in work methods engineering. Most graduates of accredited industrial engineering programs have this training.