M4E #37: Jidoka and Poka Yoke

One of the main principles behind the Toyota Production System is to avoid passing on defects in the production chain. This principle is called Jidoka, as we discussed in M4E #11. The following video from ETH Zürich reviews the Jidoka concept but it also introduces us to a new japanese term: Poka Yoke (you can jump to 5:00 if you think you already understand Jidoka). The main objective of a Poka Yoke is to avoid creating a defect and sometimes to alert as soon as possible when an error has occurred (although of course the first type is the most desired one). Find more about this concept in the video:

Time for Insights

• The term comes from the verb yokeru, that means to avoid, and poka, that means mistake. Hence the meaning of mistake avoidance when combining both words. Also, as told in the video, the first term used was baka yoke, meaning “idiot proofing”.

• As told before, Poka Yokes may be prevention-based or detection-based. The first type aims to design a process where the possibility of a mistake is avoided from the beginning. This is the case of an old USB that can only be plugged in one position but a better poka yoke is the case of a USB-C, where it doesn’t matter how you plug the connector. The second type is not able to avoid the mistake but to detect it to avoid sending a defective product to the costumer. A quality control process with its checklist or a computer vision algorithm looking for defects may be some examples.

• A brief reminder of poka yoke types depending on the method used:

  • Contact method. Depends on physical attributes and contact between pieces or tool to avoid making mistakes.

  • Motion or sequence method. It’s designed to only allow a specific sequence to be made.

  • Fixed-value method. It only allows to perform a fixed value of movements/operations or set up a fixed number of pieces.