The Poka-Yoke Method: Your Best Tool for Avoiding Mistakes

To err is human. Even though we all make mistakes, it’s always a relief when we catch one just as it’s about to happen. Forgetting to put your cup in place to catch the coffee machine’s sweet nectar has minor consequences. After all, cleaning up a mess isn’t the end of the world! However, the consequences of a mistake can be severe when a company’s image or people’s lives are at stake.

That’s why it’s so important to put preventive mechanisms in place. Poka-yoke is just that—a simple but effective method for preventing problems. Find out where the concept comes from, why it’s beneficial, and how you can use it.

Where does poka-yoke come from?

Originally, poka-yoke was called baka yoke, a term that means “idiot-proof.” Understandably, the expression has since been modified, because nobody likes to be called an idiot. The more diplomatic poka-yoke means “error-proof.” baka yoke, a term that means “idiot-proof.” However, this expression has been modified and we understand why: no one likes to be called an idiot. More diplomatic, poka-yoke means “error-proof”.

“Achieving zero defects is entirely possible.” — Shigeo Shingo Shigeo Shingo

The concept of poka-yoke was created by Shigeo Shingo, an industrial engineer at Toyota, the company behind LEAN. Noticing that the factory workers responsible for making a switch frequently forgot to install a spring under one of the buttons, he modified the procedure to include an additional step that resolved the problem. The minor change had workers prepare the necessary springs first and place them in a reserved space before inserting them into the switch. If a spring was left in the reserved space, the employee noticed and could correct the error.

Why does poka-yoke contribute to continuous improvement?

Rather than demanding perfection, poka-yoke recognizes the inevitability of human error and provides a framework for avoiding it, or correcting it quickly if necessary.

In addition to the clear advantage of reducing the number of errors, it provides a simple strategy for dealing with typical problems that can be easily avoided. It also makes it easier to analyze a situation and make decisions. Everything looks good? Move on to the next stage. There’s a problem? The cause can be easily determined. 

Three real-world examples of poka-yoke

Essentially, poka-yoke is a behavioural restriction that prevents moving on to the next step until certain conditions have been met. Here are three real-world examples to help you better understand this lesser-known method.

1. Car safety

Cars are equipped with several safety features. Some dashboards make a warning sound if a seatbelt isn’t fastened or a door is left open. Warnings may also sound when you’re too close to an object or the middle of the road. Manual transmission requires the driver to engage the clutch for the car to start.

2. Microwaves, washing machines, and trains

All of these machines have mechanisms that stop them from working when the door is open. The same goes for dishwashers and elevators. This is an important control function that prevents them from starting unless certain conditions are met.

3. Spell checker

Many of us use spell checkers to spot and correct mistakes in our writing. The tool helps us fix embarrassing mistakes before we press the “Send” button.

When to use poka-yoke

Although it comes from the automotive sector, poka-yoke can be adapted to all areas of activity and businesses of all sizes. Indeed, this approach can be applied in any circumstance where error is possible. It is both simple and comprehensive. 

There are 3 types of poka-yoke: prevention, detection, and correction.

1. Contact method poka-yoke, to prevent errors

This type of poka-yoke prevents mistakes with the help of visual or physical elements. Examples include adding a quality control station to a production line or hiring a copy editor to correct a report before sending it to the customer. 

Contact method poka-yoke can also involve the shape, size, weight, or colour of a part. These physical characteristics can be designed to prevent incorrect assembly. For example, a USB key can only be inserted one way.

2. Fixed-value method poka-yoke, to detect errors

is type of poka-yoke involves a signal that indicates an error or a condition that must be met. Here are a few examples:

  • A sound that signals when a car door is open
  • A counter that shows the number of pills in a container
  • A sticker that indicates which side of a box is upright to avoid spilling or breaking its contents
  • Colour-coded labels that match a tool to the step of the process when it is used
  • A colour code to prioritize files

3. Motion-step method poka-yoke, to correct errors

This error-proof system ensures that the steps are carried out in the correct order. It is found in many situations. Among other things, we must follow specific steps to:

  • Start a device;
  • Assemble a piece of furniture;
  • Build a Lego;
  • Fill out an online form (it won’t send if it’s incomplete)

This type of poka-yoke also makes it possible to correct errors automatically. For example, scanning an item automatically enters the right information into a computer system.

Seven simple steps to implement poka-yoke

Poka-yoke is easy to implement. Read the seven steps below to see for yourself!

  1. Make a list of the essential steps in an activity (e.g., going through emails) or process (e.g., the billing process).
  2. Make a note of the common mistakes.
  3. Determine the cost of these mistakes (wasted time, money, materials, etc.).
  4. Figure out the root cause of the mistake or problem.
  5. Choose the best solution and implement it.
  6. Test it to see if it works.
  7. If necessary, make improvements to your solution.

In short, every organization has many processes made up of thousands of steps carried out by dozens or even hundreds of employees. As such, the risk of error is high. The purpose of poka-yoke is to eliminate the need to correct avoidable lapses at the source. 

Eliminating these sources of error reduces the pressure on your employees while increasing the reliability of your processes. The result is improved products and services. Furthermore, simplifying processes using the poka-yoke method allows employees to focus more on creating value by putting their ideas to work, rather than using their concentration to avoid making mistakes.

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