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poka yoke
10 Feb 2021

Poka-Yoke Method in Manufacturing

Poka-Yoke is a Japanese word that means “mistake-proofing”. This method was first introduced by Shigeo Shingo while working at Toyota.
We all know that human errors cannot be completely removed. We always do some mistakes in our daily life inadvertently. We take care of those mistakes but even after this we repeat a few mistakes again and again.
These types of human errors are very common in the manufacturing industries. For example, a worker or operator may forget to assemble an important part in the final assembly or he may forget to execute any important process step such as pressing the coolant on switch while cutting operation on the machine. The mistakes may be due to wrong perception, incorrect execution such as setup error, operational error, measurement errors, use of incorrect process or part.

When we face these kinds of similar situations again and again then we have to find a permanent solution of that problem.
The use of Poka-Yoke aims to eliminate the root cause of such problems in the manufacturing industry. For example, the operator will not be able to assemble all the parts in the final assembly without a proper order or without taking all the necessary steps in the final assembly.

poka yoke
Here, I would like to discuss a practical example of the manufacturing industry. An operator on the gearbox assembly line usually forgets to insert the circlip in bearing housing. This circlip is used to hold the main shaft bearing in the bearing housing. In the absence of circlip, the bearing may come out and it may cause product failure.
This error is removed by providing a stopper on the assembly line conveyor. This stopper doesn’t allow the conveyor to move forward whenever the proximity sensor doesn’t sense the circlip. The operator has to put the circlip in front of the proximity sensor to move the assembly line conveyer. In this way, the operator will never miss the circlip in the gearbox assembly.

The Poka-Yoke method eliminates the part defeats by removing the possibilities of mistakes occurrence before it reaches the end-user. It not only reduces the rework but also improves the quality of product which may degrade due to rework.
Poka-Yoke was first introduced in the manufacturing industry but now we can see Poka-Yoke examples in all sectors. Poka-Yoke is also present in our daily life. For example, a cut mark on the mobile sim card is provided to remove the confusion of proper placement in the mobile phone.

It is also used in the car safety features, like an indication of door open when the car engine is in running condition or the seat belt is not fastened.

Besides this, we can see it in washing machines, microwaves, elevators, treadmills etc.
It is also used in electric switches like 3 pin switch and in computers like USB plugs.
The main purpose of writing this blog is to understand the concept of the Poka-Yoke method and to develop the ability for implementing it to our daily or professional life problems.

Dr. Amit Kumar
Associate Professor-ME Department