The point of going Lean is to eliminate waste. Toyota defined three broad types of waste: muri, mura and muda.
Muda is Japanese for waste. It refers to any human activity, which absorbs resources, but doesn't directly add customer value. Non-value-adding activities and results should be eliminated.
Mura is the variation and inconsistency in quality and volume in both products and human conditions.
Muri is the unreasonable work management imposes on workers and machines because of poor organization. Muri is the act of pushing a person or a machine beyond its natural limits (carrying heavy weights, moving things around, dangerous tasks, even working significantly faster than usual) Muri also includes bad working conditions and is almost always a cause of multiple variations.
Taichi Ohno, long considered the father of the Toyota Production System, identified what are called the seven wastes (an eighth waste was later added):
- Over Production: producing too much of a product or service or before it is needed
- Transportation: movement of materials, products or information that does not add value
- Inventory: more information, project, material on hand than the customer needs right now
- Waiting: inactive or lost time created when material, information, people or equipment is not ready.
- Motion: any motion that is not necessary to successfully complete an operation or task
- Defects: work that contains errors, rework, and mistakes or lacks something necessary
- Over-processing: efforts that create no value from the customer's viewpoint
- Skills: underutilization of employee skills and knowledge.
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