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Poka Yoke: 4 Steps of How to Set up Mistake Proofing【Toyota Production System】

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Poka Yoke: 4 Steps of How to Set up ...

Poka-Yoke is a way of thinking and method to create a state where mistakes do not occur. There are two main types of Poka-Yoke. Forced Poka-Yoke and Caution Poka-Yoke. Introducing 4 steps to design and introduce this Poka-Yoke in the workplace along with a case study.

(Duration: 5:10)

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What’s “Poka Yoke” that is said to aim at zero defects?

Hi, this is Mike Negami, Lean Sigma Black Belt.

The Poka Yoke is very famous in the manufacturing industry. Pretty much everyone knows the word in the industry.  “Poka” means a “Mistake” and “Yoke” means “To Avoid” in Japanese. Therefore, Poka Yoke means “Mistake Proofing”.

Since we are all humans, everyone makes mistakes. However, mistakes in business could lead to major losses or safety issues.  Ideas and techniques that ensure mistakes never happen are Poka Yoke.

Application Examples of Poka Yoke

The most familiar example is a USB cable. This cable, you’re not physically able to plug it in upside down.  Another example is, one of my house’s under sinks looks like this underneath. If by any chance you dropped something important in it, you can still get it out of the pipe. This is also Poka Yoke.

In the manufacturing industry, there are two types of Poka Yoke: Control Poka Yoke and Warning Poka Yoke.  Control Poka Yoke is more ideal. By changing process steps or tweaking your tools,  Control Poka Yoke is to make it mechanically impossible for a mistake to happen in your process.

If you can’t achieve Control Poka Yoke, you should consider Warning Poka Yoke.  This Poka Yoke alerts operators by color or sound when they are about to make a mistake, so they can prevent it.

A car’s headlights are a good example. When you leave your headlights on and stop the engine, the previous generation of cars alerted us by sound. This is the Warning Poka Yoke.  But recent cars turn the lights off by themselves. Cars have evolved and now do the Control Poka Yoke.

The 4 Steps of how to establish your Poka Yoke.

So how can we utilize Poka Yoke in our work or company? I’ll introduce the four steps to carry out a Poka Yoke.

1) Keep firmly in mind: “Everyone makes mistakes, but I’m responsible for those mistakes as a manager.”

You may think that that is just a mental theory, but as long as you blame others or your workers, you cannot think of any Poka Yoke ideas.

It’s more important than you think to change your mindset to “I’ll make a Poka Yoke process. In order to do that, what should I do?”  In service operations, since we didn’t have this concept before, and we have few examples, this mindset is particularly important. We can go to the next step after achieving this.

2) “Find the most mistake-ridden work or process.”

In Lean Sigma, we always deal with Vital Few, a few very important factors. The impact after solving the vital few mistakes is more significant than solving the others.

3) “Find the root cause of the vital few mistakes and design Control Poka Yoke or Warning Poka Yoke.”

For that, you should conduct the 5 Why Analysis and make an Ishikawa Diagram, then you can find their root causes.

4) “Make an SOP (Standard Operating Procedure) and Checklist, then train operators according to it.”

For operations using Excel or PDF, you may be able to practice actual Poka Yoke, for example, by using the data validation function or Macros.  But, frankly speaking, you may have rare chance to be able to set up Poka Yoke for service operations.

In that case, you should design a standard operation that produces less mistakes and document the standard operation as an SOP.  You should also make a Checklist that lists the important steps of the new process.  Have the operators check this Checklist during their operations.

Also, the new method must be user-friendly for the operators, otherwise, they would stop using it and return to their old method.  Please aim for zero mistakes with this Poka Yoke concept.

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