Poka-Yoke | you can’t go wrong

Summary

Poka-Yoke: a simple idea that eliminates defects. Yes, makes it impossible to make an error. We are surrounded by Poka-Yoke kind of devices. This article explains what Poka-Yoke is and shows a few examples of Poka-Yoke devices as well as Poka-Yoke methods.

What is Poka-Yoke?

Even if you have never heard of Poka-Yoke you have certainly used more than one. Perhaps even on a daily basis. Poka-Yoke is as old as the ancient floppy disc (which can be inserted into the drive one way only), or perhaps even older.

Poka-Yoke is a device or method that prevents people from making mistakes. The word in Japanese means mistake proofing or error proofing. Originally the word Baka-Yoke or idiot proofing was used, but someone probably figured that even those of us who are not idiots make mistakes at times so now we use the word Poka-Yoke, and no reference to stupid people is made.

How to fight with defects?

The Toyota System or Lean Philosophy aims for perfection (it isn’t called Continuous Improvement by accident). In manufacturing producing sporadic defects is better than making frequent defects, but what if one defect can destroy the brand’s reputation or -  even worse – put people in danger? In any case, each defect has the potential of pushing customers away from us and closer to our competitors. Traditional management’s first response would probably be something to the effect of setting up an effective quality check department. Let’s think about it.

Quality department – do they eliminate defects?

A quality department usually operates in one of two ways. It can either check some products (for example – every 10,000th piece that leaves the production line) or every single product. The first option will definitely raise the standard of plant’s quality but it will not completely eliminate defects. The second option, checking every single piece produced or watching to make sure that every time a service is provided it is done the right way – is either very expensive or often impossible. Imagine fast food restaurant manager standing inside a restroom and making sure the staff wash their hands every single time they leave. I guess it’s possible, but who can guarantee that the manager won’t accidentally skip someone or favor some people?

Defects from Lean Perspective

Let’s look at the problem from the lean perspective. Producing a defect followed by detecting it and finally fixing it (or throwing it away) is Muda. Wouldn’t it be better just not to make the mistake in the first place? It’s not always possible, but wherever it is – let’s create a device (Poka-Yoke device) or develop some habits (Poka-Yoke method) that will simply make it impossible to make a mistake. For example – if we don’t want people to be exposed to harmful microwaves – why don’t we install a simple device in microwave ovens that automatically turns off the oven as soon as the door is opened? Or – if we don’t want to break an ATM machine – why don’t we cut one corner of a credit card to make sure there is only one way it can be inserted? If our kids keep losing that TV remote, why don’t we tape a piece of paper on the coffee table, trace the remote on it and then show the kids that this is one and only place where the remote can be placed after it’s used (this last method reduced the remote control loss rate from 3 times a day to probably once a week!)?

Here are some other examples of Poka-Yoke devices:

And here are some examples of Poka-Yoke methods:

In companies where the Toyota System is used, Poka-Yoke devices are created every week or even every day. The Kaizen idea suggests that they don’t have to be expensive and they are usually very simple. Every company, office, hospital, home, etc. where certain mistakes are not wanted, but where imperfect beings work or live, should give the idea of Poka-Yoke some thought. It might make a big difference.

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