This is a short chapter. The chapter seems to act as a thematic bridge. Taiichi Ohno begins by talking about the importance of making a mindset shift in order to achieve breakthrough kaizen results, and ends the chapter by talking about the misconception of economies of scale. In the chapters following this one Taiichi Ohno argues against large volume production based on equipment utilization, traditional cost accounting, and local optimization. He introduces that theme by saying This is not common sense. Get ready for a different way of thinking.
When a misconception becomes accepted as common sense progress stops, says Taiichi Ohno. For example there may be a way of doing things that is not great but is low risk so that becomes the accepted norm. Even if the rewards are small, if the risk is small then this is often the preferred method under “common sense”.
Ohno argues for a change of mindset “to go beyond common sense”. He says that it’s better to go after the big reward, recognizing that there may also be big risks. These big risks simply need to be counteracted. It takes courage to step outside of common sense, but this is the way “to go beyond”.
Whether it’s top management, middle management, workers, or labor union representatives, people tend to accept common sense, even if it is wrong. People may think a certain method is the best, or even know that it is not but accept that it can not be changed.
If you do kaizen based on an extension of your current thinking, your results will be limited to 10% or 20% improvement. Ohno says you have to turn your thinking upside down. To find a new path to success, a mindset revolution is required from everyone in the organization.
This is particularly true when implementing one-piece flow. People think its common sense that making a large batch of parts is quicker than working on one piece at a time. In fact, traditional cost accounting will tell you that after a changeover it’s cheaper to run 10,000 pieces on a press instead of 1,000 pieces. It’s no wonder that misconceptions hide within “common sense”.
At the closing of the chapter Taiichi Ohno relates the story of a question he once received. “If Toyota was able to reduce changeover times on a press from 1.5 to 2 hours down to 10 minutes, why not produce a 20,000 piece run instead of a 10,000 piece run?” The argument was that now that you have more available press time you should produce more in the time saved through SMED and quick changeover kaizen.
Ohno ends by saying that this is such a different way of thinking so that giving a direct answer to this question would have been useless. Yes, that may be what the arithmetic says… was Ohnos answer.