Lean Manufacturing and Six Sigma Definitions

Glossary terms, history, people and definitions about Lean and Six Sigma


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TWI is an acronym for Training Within Industry.

It was created by the United States Department of War, running from 1940 to 1945 within the War Manpower Commission. The purpose was to help war-related industries whose personnel were being drafted into the US Army at the same time the War Department was ramping up additional orders. The shortage of trained and skilled personnel at precisely the time they were needed most would impose a hardship on those industries, and that only improved methods of job training would be able to handle this challenge.

It was later incorporated into Japan after World War II, led by Lowell Mellon from TWI Inc., who had been a TWI instructor in the United States during the war. It was later popularized in the Toyota Production System with the help of Isao Kato.

There are three main parts to TWI:

  1. Job Instruction (JI) – a method for trainers (supervisors and experienced workers) to train inexperienced workers faster. The instructors were taught to break down jobs into closely defined steps, show the procedures while explaining the key points and the reasons for the key points, then watch the student attempt under close coaching, and finally to gradually wean the student from the coaching. Download a free template from BPI
  2. Job Methods (JM) – a method for workers to objectively evaluate the efficiency of their jobs and to methodically evaluate and suggest improvements.
  3. Job Relations (JR) – a method for supervisors to deal with workers effectively and fairly.



Using the t-shirt folding process video above, here is an example of a Job Instruction sheet.


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