Poka-Yoke is not a Joke

A 10 minutes reading about How Stove Knobs Position Can Save a Million Lives and Why Everybody MUST start to value a Poka-yoke working environment.


Disclaimer: The following writing is based on writer’s actual experiences working as Automation Engineer for some manufacturers. In order to respect and protect the companies confidentiality, the name and picture of the related product and companies will not be shared.



Before reading further, I want you to choose by heart which of these designs do you prefer:

Slightly, the difference between those two designs is minor. Now, let’s think again, is the design you choose makes people-in-hurry tend to shut the fire at the correct knob? Will left-handed user get the same comfort by the design you choose?

No matter how hard we practice or we spend money on safety equipment, mistake and misunderstanding are inevitable. People grow with different languages and different habits. And not all people are born with perfect sight, there are 3 million population of color blind, suggesting that color indicator is not effective to these 3 million users.

Checklist becomes one of the most used tool to avoid mistakes. It is easy for everybody to follow this method, especially those who grow with consistent habit and strong self-discipline. Ironically, it is usually generating more confusions that, ergo, not a fully “Error-Proof” method. Moreover, checklist method is also not “Fraud Proof” because how easy it is for people to submit checklist without providing the evidence for each points

Poka-Yoke is firstly coined by Shigeo Shingo in Toyota Production System. Poka-Yoke is often literally dubbed as “Error-Proof”. Although the translation is accurate, nonetheless it strips the sense of its practicality. The simplicity is the crucial aspect that differs the idea of Poka-Yoke from “Error-Proof”. In Poka-Yoke concept, the design won’t be too much text, too much color code, or too much steps. Its intuitiveness to any kind of users whether it’s a man/woman/senior/children/foreign/person with impairment, disability, or handicap, makes Poka-Yoke becomes valuable aspect in Japanese Manufacturing. Back to our stove knobs, for casual user it seems the design is just mere a design. Either way, the stove will function similarly. But in reality, the design is a great asset to save million lives and million dollars too. Let’s talk about this more in detail.

Accident is No Laughing Matter


Other than passport and tickets, connector plug converter becomes one of the must-to-bring item during traveling. Even if you forgot to bring it, you can find it quick in the airport whereas it is the most needed item to carry other than neck pillow and foot warmer. Imagine if power connector plugs have similar shape and size wherever you go, so you don’t need to buy or carry converter. Sounds like a nice dream, but actually it is disastrous idea.

Type B plug can be 100-127 V. Type B has three legs where the third opening is function as ground to lead the escaping electric current to the ground. This is commonly used in USA and Canada. Type C is almost always 220-240V, which is commonly used in Europe, Asia and South America. If you are using 110V appliance to type B power supply, as soon as the power is switched on, the overvoltage may occur and you must do a fire drill immediately. As you can see, the third opening in type B other than protect the user by providing ground, it gives different shape plug that is Error-Proof enough to avoid misconnection. No matter how poor your sight is or how outdated you are to technologies, you won’t ever experience a fire caused by connecting your phone charger to local plug during travelling. Thanks to a Poka-Yoke Design on this plug.

From One Scratch to One Planet

As you go to stationary store, you might find a box of green 2B pencils that its lead opacity is ideal for shading multiple choices in National Examination. We are talking about the green 2B pencil with golden ring on its tip and golden engraving of its brand. The price of the pencil is not as expensive as the artist’s pencil, but the design of its body looks like an expensive pencil, the green and golden color reminds us to Harry Potter’s House of Slytherins. As the lead’s quality is mainly important, the golden ring on its tip is not less-important than the lead. The golden ring is function as the aesthetic of the pencil. Nothing less, nothing more. In the manufacturing, smudged or cropped or shifted 5mm golden ring is considered as fail product though its lead quality has met the standard and usable for shading multiple choices on exam. So this ‘fail product’ will be going to the trash bin once its flaw detected by vision sensors.

In 2019, it is estimated, there are 10 million factories in the worlds. Yearly, it may reach $ 8 trillion worth waste caused by manufacturer. So, It is not an exaggeration fact one scratch in a product can become one damage to a Planet.

The good news is, most manufacturer are already aware of pollution and willing to make solution to improve that. For product that contains papers, woods, and other organic materials, the waste issue can be minimized by donating the products. The other way to reduce the waste for smaller size product, if the damage is still tolerable, the manufacturer would do a rework. Now, what if there is an undesirable scratch in the body of car parts? The problem is even more complex than the pencil and I’d rather discuss it further on the next point.

Of Course, It’s about Money too

In automotive product, people demand safety, comfort and luxury. A single scratch on car body may be perceived by the customer as a failure on providing safety and comfort and it is not worth million dollar to purchase the car.

The condition above becomes the main reason why a 2 cm scratch in a body part that weighted 90 kg is considered as huge damage. In a year, automation manufacturer can produce averagely 90 millions vehicle. Automotive industries are expecting to keep up the number, discarding the pandemic affected the production. In order to achieve this targeted total production, machine and workers are expected to be able to produce the part in a single flow without producing waste, reworking or analyzing error in the production. Most importantly, the process must not produce more waste in order to avoid the penalty the manufacturer must pay for the industrial waste. And this penalty we are talking about costs thousand to million dollar. It is indeed not a small amount of money.


This is not a joke or exaggeration. This is painful truth about how one small damage can generate more global problem. And the idea of Poka-Yoke is still overlooked by non-Japanese factories.

Be it in hospital, in airport, in oil rig, or even in a casual birthday party, Poka-Yoke is not a joke. Fortunately, there are so many resources you can study more about applying Poka-Yoke into the existing working environment. Best book to improve safety and error-proof working environment: Meltdown: Why Our Systems Fail and What We Can Do About it by Chris Clearfield and Andras Tilcsik. Best book to learn further about Poke-Yoke: A Study of the Toyota Production System by Shigeo Shingo


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