Taiichi Ohno starts by explaining the difference between an automatic loom “working” and “moving” or “running”. Working implies that jidoka prevents it from making defects. A machine “running” and producing defects is not a machine “working”. If the machine makes a defect, it should stop. The difference between automation and jidoka (autonomation) is that in the former the machine is “running” and in the latter it is “working”.
According to Ohno the definition of autonomation (jidoka) is as follows: “A machine that incorporates an automatic stop device is called autonomation.” His schooling was in mechanical engineering at a polytechnic high school, and during a class on textile manufacturing he was taught the definition of autonomation (jidoka).
“For decades I believed that for a machine ‘to work’ meant to have an automatic stop device, such as sensors, built in to shut the machines off” says Taiichi Ohno. He explains that his polytechnic high school was near Kariya, which is the location of Toyota Loom Works. “My teacher on textile manufacturing must have studied their autonomation (jidoka). There were probably no other schools teaching this definition.”
Ohno explains that this thinking led to the idea of having operators stop the lines manually when it was difficult or impractical to attach sensors to a manual operation. This also resulted in moving conveyors with “stop the line” pull cords and andon lights built in.
He relates the story of a President of one of the companies he was instructing in kaizen who complained that Ohno would only teach them how to stop making things, not how to make things. What a simple yet powerful lesson in built-in quality!
The whole point of stopping is to make problems visible. The first step is to instruct the workers when to stop the line. The idea of jidoka with built-in quality through the autonomous stop capability begins with making it easy for workers to shut the machines off.
Once the workers begin to shut the machines off frequently, managers and engineers will think harder about how to prevent workers from stopping the machines. This leads to quality kaizen by reducing the reasons that workers need to stop the lines.
Taiichi Ohno observes that this style of assembly line is rare in the world, and even in Japan. One of the first things that Daihatsu and Hino (Toyota group companies building trucks) were told to do was to install stop buttons on the lines. The next step was to make the lines stop without human intervention.
Taiichi Ohno says that to do kaizen you have to think of ways to keep the worker from stopping the line. This is not to be confused with preventing the worker from stopping the line when they should, but rather it is to eliminate why workers would stop the line for reasons of quality, safety or inability to complete the task within takt time.
In the 1950s the kaizen and cost reduction efforts at Toyota led by Ohno focused on the fundamentals of quality and safety. Quality defects are pure cost, and any improvement in quality defects led directly to cost reduction.
Taiichi Ohno says “When we first started doing this I used to tell the workers on the assembly lines at the Motomachi factory ‘If you feel tired, shut the machines off!’ That way the team leader or supervisor would have to think of ways to prevent the worker from getting tired.” That is the humanistic way to do kaizen.