Poka Yoke technique is one of the most precious gems in the crown of Lean management. It is a way of ensuring quality without actually having a quality assurance process, rather preventing defects to appear in the first place.
Also called: poka-yoke, fail-safing. Mistake proofing, or its Japanese equivalent poka-yoke (pronounced PO-ka yo-KAY), is the use of any automatic device or method that either makes it impossible for an error to occur or makes the error immediately obvious once it has occurred. It is a common process analysis tool.
When you shop online, the credit card number you input has to be accurate, otherwise you cannot complete your order. That’s an example of error proofing, or mistake proofing.
Error proofing is best when it prevents error from occurring. If that’s not possible, the next best thing is to facilitate the work so that errors are minimized. Lastly, if errors do take place, then detection should be made obvious and immediate, or be automated.
There are basically three levels of error proofing. Here they are in order of preference.
- Prevention.
- Facilitation.
- Detection.
The first and most preferred is error proofing by prevention. An example is the traction control system in cars. It works actively full-time to prevent wheels from over spinning on slippery roads or low friction surfaces. Regardless of how good or bad the weather is, or the driver is. Prevention-based error proofing is also possible in processes. For example, in-store pickup of a prepaid online order. In addition to showing a driver’s license, the same credit card must be scanned for the system to authorize and process the pick up.
If prevention is not possible, then the next choice is error proofing by facilitation. An example of this is anti-lock brakes, in which the car helps facilitate your application of brakes in an emergency, so it is done efficiently, effectively, and the brakes don’t lock up. Similarly, in processing transactions, dedicated pre-programmed buttons such as those on point of sales systems, for items/products are used. Also, you can connect your point of sales system to inventory management. It can help you track inventory and prompt you when and how much to order. Facilitation-based error proofing makes it easier and it minimizes errors, but it does not prevent non-compliance due to forgetfulness or human error such as pressing the wrong button by mistake.
If prevention or facilitation is not possible, then employ the third choice, error proofing by detection, where detection of errors is immediate, either by being made obvious or by automated detection. An example is the annoying beeping sound and warning light in your car to alert you when you forget to put on your seatbelts. Another example, is the fuel gauge where the warning light comes on when the gas tank is low with a range of less than 30 miles left.
To summarize, if prevention is not possible, use a combination of facilitation and detection. An example is a combination of anti-lock brakes, seatbelts, and airbags. So prevent errors if possible. If not, minimize errors or at the very least, detect and mitigate these effects immediately.