What is Poka Yoke is a common question. As is true with many Japanese terms, they carry a level of mystery and intrigue that is not really merited. You see, in North America, Poka-Yoke is more commonly known as mistake-proof or error-proof.
But even that doesn’t really carry the full meaning of the Japanese term. There’s a little bit more.
Idiot-proof would be a more accurate term that is in the spirit of what the Japanese Poka-Yoke means, but not in a mean way. What I mean is that no matter who the person is, what their physical or cognitive ability, can they perform the activity and process and there are enough robust prevention measures such that the person doesn’t make a mistake?
That’s what Poka-Yoke really means.
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Below are the other elements of the Toyota Production System.
Poka-Yoke and Zero Defects
In terms of identifying defects, eliminating defects, and preventing defects – the former two have a cost. While preventing defects have some costs, it is the only true way any firm can approach zero defects – that is by preventing defects all-together.
In other words, the costs grow exponentially as there are fewer and fewer defects, but Poka-Yoke allows us to reach that by preventing defects in the first place.
Poka-Yoke and Role in Lean
Poka-Yoke is an approach that can be taken as a countermeasure to known and verified root causes. In other words, once the root causes are known through root cause analysis and the 5 Whys, then Poka-Yoke can be an applied countermeasure to make sure the error doesn’t happen again. So, think of this structure and how Poka-Yoke fits in the larger framework of Lean:
- Defect: My 1 year old keeps getting up during dinner and disrupts family dinner time.
- Root Cause: My 1 year old has free reign over everything.
- Countermeasure: Prevent my 1 year old from having free reign. To do that, I can get a baby seat with a seat belt appropriate for a 1 year old.
This is just a simple example, but you get the point.