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The Three Methods of Poka-Yoke

This sounds like a game you play, but the term poka-yoke is really a Japanese term and it means “mistake-proofing.” As a quality tool, the concept behind it is that everyone makes mistakes because we are all human. Poka-yoke either eliminates or at the very least greatly reduces the opportunity for us to make a mistake. This action will instantly reduce defects that stem from mistakes. This action will make the day-to-day processes run smoothly with decreased time, and this alone will make manufacturing cost less money and improve the quality of the product.

Here are the three methods to know:

  • The Contact Method: This method will physically put a deterrent using the shape, size or color of the item. For example, if one constant mistake is that a part is placed upside down on the product, the design is altered so that the only way to place the part is the correct way because it only fits if placed correctly. This could include a switch that limits or prohibits incorrectly installing parts.
  • The Constant Number Method: This could also include a fixed number of parts used. If a set number of movements are not made, there is an alert. Another example would be that a certain number of parts are at each step in the process. If you have parts left over, that means something went wrong. All parents have experienced this at one time or another while building a bike or a piece of furniture for their kids.
  • The Sequence Method: A set amount of prescribed steps are in said process before the next stage is rendered. This could be boxed opening in a certain sequence, color coding, and tagging, and then inspecting to ensure that important steps were completed. The theory behind poka-yoke is if it can’t eliminate the chance of error completely, then there should be an immediate warning. 

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