Mistake Proofing Using Poka Yokes

Even after all the careful planning, Murphy’s Law, which states that “anything that can go wrong will go wrong,” remains a major headache to management. To counter this, one of the most effective solutions is the Japanese method called “Poka Yoke,” which means mistake or failure proofing.

Although many techniques of Poka Yoke were known a long time before, the term itself was coined and systematized by Shigeo Shingo, an industrial engineer in Japan during the 1960s. He was one of the key proponents of the quality management revolution that propelled Japan’s manufacturing industry.

The main idea of Poka Yoke is the prevention or minimization of errors by designing the process so that mistakes can be avoided or detected as soon as possible without relying on correct human behavior. It anticipates possible human errors and builds safeguards against it. Because of this, Poka Yoke once meant “fool-proofing”. However, the negative connotation forced the more politically correct definition “mistake proofing.”

Poka Yoke And Business

Adopting Poka Yoke techniques produces large improvements in quality, not only in manufacturing enterprises but also for those in the service industries. Surprisingly, most of the techniques require little or no capital investment. Management will just need to have a determined quality mindset to sustain this effort.

The creation of suitable Poka Yokes is for everyone in the organization. Even the lowest ranking worker may be able to come up with good ideas for mistake proofing. It is therefore best to get everyone involved.

Poka Yokes are often divided into two basic approaches. The first is the prevention Poka Yoke, also called “shut out type.” This works by notifying or stopping an action or process before an error is committed. Here are just a few of the everyday applications of this concept:

•There are many items that are designed to be child-proof. One of the most common examples is the safety door locks on cars.

•The anti-lock braking system in many new cars works by automatically controlling the pressure exerted on the brakes so that it would not lock.

•In the industrial paper cutters used in printing press, the operators normally operate the cutter by pressing with two hands. This prevents the blade from cutting off his hand due to carelessness.

•The fuses and circuit breakers found in every home, office and factory prevent fires from occurring by stopping the flow of electricity if it reaches dangerous levels.

•Even the simple window envelope is a good example of a prevention Poka Yoke. The addressee is typed on the letter and is seen thru the window and so it is impossible to send the letter to the wrong recipient.

The second basic approach is the detection Poka Yokes, also called “attention approach.” This type stops or gives notice of an error or problem so as to prevent further damage. In this case, there is already something wrong going on.

•In a car’s dashboard, there are many warning lights that indicate a potential problem like overheating. Normally the driver could take some corrective action before the condition worsens.

•Notice that just before you cross some parts of the LRT, there are horizontal bars that are of the same height clearance as the LRT. If your vehicle happens to be too high, it will hit the horizontal before it hits the LRT. This will cause less damage to your vehicle and to the LRT.

•The fire sprinkler systems in buildings automatically turn on when sign of a fire is detected, or if a certain temperature is reached. There is less cost or damage if a prevention approach is used. Even though it would seem to be obvious that prevention should be preferred over the detection approach, oftentimes there are technical or financial reasons why this is not possible or suitable.

Once you have settled on whether to use the prevention or detection approach, you must then determine what type of Poka Yoke is needed to improve the process. There are at least three types of Poka Yokes to choose from:

1.Contact type. This is the use of a physical property like shape, size, etc. for detection or prevention of error. An example of this is when an attachment is designed not to fit in a wrong socket.

2.Constant number type. When a fixed number of actions are not accomplished, a warning is shown or it does not work. This is commonly used in data entry forms to make sure it is complete.

3.Performance sequence type. This is to make sure that all the necessary steps are performed in the proper sequence. An example of this is a step-by-step check list.

*Originally published by the Manila Bulletin. Written by Ruben Anlacan, Jr. (President, BusinessCoach, Inc.) All rights reserved. May not be reproduced or copied without express written permission of the copyright holders.