What is Poka Yoke?

Definition

Poka Yoke (pronounced Poh-kah YOH-kah) is a concept of mistake proofing processes to result in zero defects. The concept originated at Toyota and is credited to Shigeo Shingo an engineer at Toyota (and author of various books on lean methods using the Toyota production method).

Why is Poka Yoke important

The concept of Poka Yoke is a fairly simple one – mistakes will not turn into defects if “worker errors are discovered and eliminated beforehand”. Poka Yoke depends on creating simple yet effective visual methods of inspecting the quality of what is being produced and deploying simple efficient systems for highlighting and preventing defects. Often Poka Yoke depends on three different types of inspection (as defined by Shingo) – these are:

* Judgment inspection – sorting the defects out of the acceptable product
* Informative inspection – Operators inspects their work or the work of the prior operator – thus ensuring quick feedback along the production line and the rework of defects at a stage where they are easier to fix.
* Source inspection – ensuring that the conditions for a quality production environment exist.

Prior to deciding where to place mistake proofing systems it’s important to be able to identify the process step where the defect occurs (often where information inspection is being used this is made easy because it is likely to be the previous step).

Poka Yoke represents an easy to implement and rewarding system of mistake proofing – and you may be surprised to learn that various examples exist in day to day life. For example paint that goes on pink then dries white offers a visual tool to check for areas that haven’t been painted – old style floppy disks being designed in such a way that they could only be inserted one way are all forms of Poka Yoke.

While Poka Yoke is usually low cost, improvements can be dramatic – defining a sensible easy to implement method of removing defects can improve both production runs whilst having a rewarding impact on an organisations bottom line.