Poka Yoke

Poka-yoke: (POH-kah YOH-kay) Japanese for mistake-proofing; a poka-yoke device is any mechanism that either prevents a mistake from being made or makes the mistake obvious at a glance. The term was introduced by Shigeo Shingo, who was one of the industrial engineers at Toyota. He has been credited with creating and formalizing Zero Quality Control (ZQC), which relies heavily on poka-yoke. The term has been widely used internationally for over a decade.

For example, people sometimes forget to put their cars in park before leaving them. Car makers now build their cars so that you can't remove the key from the ignition unless the transmission is in park.

Sometimes this means adding steps, and sometimes it means eliminating steps.

Applications to software for early defect detection: http://www.campbell.berry.edu/faculty/jgrout/pokasoft.html ( BrokenLink )

Much more information, with many examples: http://www.campbell.berry.edu/faculty/jgrout/pokayoke.shtml ( BrokenLink )

One common example is making it very hard to physically install a device incorrectly. IDE cables, plugs, etc. Failure to use this techinique in designing the accelerometers used on NASA's Genesis probe (they had to be x-rayed to determine orientation!) led to a rather quick landing.

This is related to the original meaning of Murphy's Law: Murphy was an engineer, and his law was stated in terms of connectors that can be coupled incorrectly, will. (if I am recalling it correctly). His point was that if you make things to be connected, make them in such a way that they can't be put together incorrectly.

That reminds me of a true story from more than one hundred years ago. One day a steam railway locomotive returned from repair. Someone was given the job of filling it with water and lighting the fire. After some time he reported to his foreman that the pressure gauge was on zero. While he was doing this the boiler exploded causing casualties. The pressure gauge had completed a circle to the wrong side of the zero stop because the safety valve had been installed the wrong way round.

I will fill in the reference later -- JohnFletcher

See DiscoverDefectsEarly, FailFast

CategoryDiscovery