Poke-Yoke prevents errors

Poka-yoke is a Japanese term for ‘fail-safing’ or ‘mistake-proofing’ – avoiding inadvertent errors by forcing correct completion of an activity. The concept was originated by Shigeo Shingo as part of the Toyota Production system.

Poka-yoke aims either to give a (very obvious) warning that an error is being made or has been made, or wherever possible, to actually prevent it being made. Often the cost of the latter is greater, so ‘control poka-yoke’ may be limited to situations where frequent erros may be made, or the consequences of an error are particularly significant.

So, a 'control poke-yoke'preventserrors; a 'warning poke-yoke' detects errors

Where a ‘warning poka-yoke’ is used, the aim is to let an operator tell ‘at a glance’ that all is not right – and allow the operator to recover the mistake.

Poka- yoke ‘devices’ can be very simple. An example is intermediate storage receptacles into which the parts for a single assembly are counted before the assembly begins. At the end of the assembly process, any part left in one of these receptacles is a clear sign that something is missing from the assembly.

In the same assembly situation, a ‘control poka-yoke’ might be the redesign of a component so that it can only be inserted into the assembly in the correct orientation or, if this is not possible, the colour-coding of compents to show more clearly where different items connect.

A common, everday example of a poka-yoke device is the switch in a car’s automatic gearbox which prevents the engine being started if the gearbox selector is set to anything other than Park or Neutral.

A particular advantege of the poka-yoke approach is that it provides 100% inspection and therefore should automatically lead to ‘zero defects’ leaving the process.

It need not beexpensive. Toshiba, one of the biggestsupportersof Poka-Yoke, has a number of mistake-proofing devices at each workstation .. .but aims toimplementeach one for less than $150.


Productivity is my 'bag' ... it is what I know about. I am President of the World Confederation of Productivity Science -http://www.wcps.info and Director of the National Productivity Centre in the UK http://www.natprodcentre.com - go to this site for some good free resources and some (paid for but low price) e-learning on productivity. I also edit the International Journal of Productivity & Performance Management. My views on productivity and on learning (which I think are related) are su...

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