Poka-Yoke – Error Proofing (or Idiot Proofing)
Poka-Yoke is a Japanese term which means “mistake-proofing.” It is a Lean concept that was first introduced in the 1960s by Shigeo Shingo. Poka-Yoke techniques are being used today to error-proof processes, products and services to stop them from going wrong. The goal of Poka-Yoke is to eliminate defects and mistakes by designing systems so that they cannot be made wrong.
In this article, we will explore what Poka-Yoke is and some of the techniques being used to achieve mistake-proofing.
So what does Poka-Yoke mean and where did it come from?
Poka-Yoke (ポカヨケ) is a Japanese term which means “mistake-proofing” or “inadvertent error prevention”. Originally introduced by Toyota, the idea of Poka-Yoke was to design our process with safeguards so that errors would either be immediately found or simply avoided in the first place. This could be that when operating equipment or tools, the operator avoids errors and defects by preventing, correcting or drawing attention to the human errors as they occur.
Initially, Yaiichi Ohno, used the world Baka-Yoke which today translates as fool-proofing or idiot proofing. It was changed to Poke-Yoke to be a little milder.
Poka-Yoke techniques can be classified into three categories:
Prevention: This type of Poka-Yoke prevents the occurrence of a mistake. An example of this would be putting a cover over a button so it cannot be pressed accidentally. For Formula 1 fans, this was how they ensured Lewis Hamilton did not press that “magic button” by accident that cost him the potential race win in France 2021.
Detection: This type of Poka-Yoke detects when a mistake has been made and alerts the operator so that it can be corrected. An example of this would be using coloured-coded tags to identify which process step a product is in.
Correction: This type of Poka-Yoke automatically corrects the mistake. An example of this would be a barcode scanner that automatically enters the correct product information into a computer system.
Poka-Yoke is not only used in manufacturing but can be applied to any process where human error may occur. It is all about designing systems so that they cannot go wrong.
Poka-Yoke techniques can be simple and inexpensive to implement but can make a big difference in preventing mistakes and defects. Implementing Poka-Yoke techniques can help you achieve higher quality, lower costs, and increased customer satisfaction.
"Anything that can go wrong will go wrong"
Examples of Poka-Yoke
1. One Poka-Yoke technique is to use colour-coded tools and equipment. This way, the operator can easily identify the correct tool for the job and avoid using the wrong one.
2. Another Poka-Yoke technique is to use positive and negative feedback mechanisms. For example, a machine might stop working if it detects an error, thus preventing the product from being further damaged.
3. Poka-Yoke can also involve using sensors to detect errors. For example, a sensor might be placed on a machine to detect when something goes wrong and automatically shut the machine down.
4. A common Poka-Yoke technique is to use mechanical devices or physical barriers to prevent mistakes from happening. For example, a barrier might be placed around a machine to prevent people from getting too close and getting hurt.
Today, ADAS support a whole range of functionality to stop error’s taking place from parking assistance to lane departure warnings.
Common Examples of Poke-Yoke in Everyday Objects
In the broadest sense, Poke-Yoke is a behaviour-shaping constraint that creates an environment that prevents something from going wrong. Common Examples of Poke-Yoke include:
- Think about automatic vehicles. Before you can start the engine, you must have your foot on the brake to stop it from accelerating toward the wall in front of you. You even have to have it in “Park” or “Neutral” before you can start the car.
- And if you want to take the complexity of our vehicles further, consider ADAS (Advanced Driver-Assistance Systems) which support drivers in ways that were unimaginable before from lane departure warnings to reverse park assists.
- Moving away from vehicles, have a think about your medicine cabinet and how some bottles need the top to be pushed down and turned at the same time – a way to stop children from getting access.
- And if you are thinking about household objects, consider AC power plugs and sockets in the UK. It can only go into the socket in one way.
- Lastly, consider the SIM in your mobile phone. It has been designed to only fit the sim holder in one way. A simple design idea that reduces the risk of people putting their SIM’s into their phones the wrong way and potentially damaging the SIM and the phone.
Why is Poke-Yoke so important?
Without considering Poke-Yoke and mistake-proofing your processes, things are simply going to go wrong. This is Murphy’s Law which states
“Anything that can go wrong will go wrong”
This adage or epigram is spot on. If we do not design tools, processes, products and services in the right way, with Poke-Yoke to stop things from going wrong, businesses and customers will bury themselves in errors and rework at huge business costs.
Poke-Yoke and the Digital Transformation
What we are seeing today is a major push to digitalise workflows but there are two key errors being made by companies on a global scale.
Firstly, they are failing to optimise their processes before they digitalise them. This is the subject of another article.
Secondly, they are not considering what can go wrong when the data they are capturing is based on both end customer inputs and employee inputs. As we are seeing, many organisations have just not taken this into account assuming that both customers and employees will always add the data into the system correctly.
The impact is that we have a lot more bad data that is costing more to clean up than it would have done to spend some time up front applying Poke-Yoke in the design and development stage.
Learning More about Poke-Yoke
Poke-Yoke is one of those tools which are just common sense but not commonly applied. Coming up with designs and ideas to stop things from going wrong in the first place is the hard but creative part. But it’s about nudging or simply removing errors done by our users and employees through well-designed systems designed to do the right thing right first time.
To learn more, join one of our Lean Six Sigma Courses.
Summary about Poke-Yoke
Poka-Yoke is all about mistake-proofing what we do! By using Poka-Yoke techniques, we can eliminate defects and mistakes, thus improving the quality and safety of our processes, products and services. But don’t forget, that poka-yoke is just another tool to help us eliminate waste so we can deliver perfect value with zero waste. Thats the goal of Lean.
A few other examples of everyday Poke-Yoke’s
- When adding your credit card to make an online purchase, the payment gateway immediately knows if it’s a Mastercard, Visa etc. It also knows if the number is valid.
- When you are using Outlook and you mention the “attachment” in the body of the mail, you get an alert if you did not attach a document.
- You used to be able to get confused when refuelling your car by putting petrol in your diesel car or vice-versa. There was nothing to stop it. Today, new cars are begin designed with fuel nosels that match the vehicle type to avoid this issue.
- Another car example. The light comes on when you run low on fuel to remind you to refill the vehicle.
