Poka Yoke: Error Prevention Method to Stop Mistakes

Poka Yoke: Error Prevention Method to Stop Mistakes

Quality control measure for the Toyota Production System.

Businesses should work to make processes as efficient as possible. Part of that means eliminating mistakes or the potential for errors as much as possible. However, human error is a consistent variable that companies must factor in when implementing any system. Although establishing perfect processes is impossible, specific measures can improve them. 

Poka-yoke is one of the concepts that a company can use to minimise inadvertent mistakes and boost the effectiveness and efficiency of processes. Making mistakes is part of being human but we can help reduce the chances of making mistakes. According to the technique, if you know how mistakes are happening, then you can set up interventions to eliminate their occurrence.

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What does the term Poka Yoke mean?

What does the term Poka Yoke mean? ‘Poka’ loosely translates to unfortunate mistakes or carelessness, while ‘yoke’ means prevention. So poka-yoke is the Japanese term for mistake-proofing or fail-safeing. 

What is Poka Yoke?

Shigeo Shingo an industrial engineer developed poka-yoke (poh-kah yoh-keh) as a quality control measure for the Toyota Production System (Lean Methodology) in Japan in the 1960s.

Shingo, who had experience in statistical quality control, came up with the concept to improve the efficiency of the Toyota Production System. He became frustrated when he realised that even though the system had measures to detect errors, it was still difficult to deal with them at the source.

Here’s how Shingo initially developed poka yoke: In an assembly process where workers had to insert two springs in a switch, they often forgot to include one. Therefore, Shingo implemented a solution where they built a placeholder for each assembly. 

Before beginning assembly, workers would set up the springs in the holder, which made it easier to see if one of them was forgotten. According to poka yoke, the earlier you catch mistakes, the more efficient the system is. Although the concept was originally created to help in manufacturing, it applies to numerous other areas.

Why is Poka-Yoke important?

Help people and processes work together right the first time,  making mistakes impossible to happen.

Applying Poka Yoke methods in both product and process design can eliminate human error and mechanical mistakes.

What is Poka Yoke in Lean?

Poka Yoke approach is a key part of the continuous improvement process, which is central to Lean management and essential to fine-tuning processes in six sigma.

Poka-yoke is a methodology for “mistake-proofing” or “error-proofing” processes.  It is a foundational tool in Lean targeting eliminating waste, streamlining processes and increasing efficiency by reducing human error and mistakes.

What are the Types of Poka Yoke?

This quality control strategy recommends that when an error occurs, start from the beginning. Knowing why mistakes happen will make it easier to craft actionable solutions to prevent them.

Poka Yoke strategy provides three main ways to check for mistakes

Contact Method: Involves checking the physical characteristics of a system, process, product or wherever the error occurs. Examples of attributes to analyse include temperature, size, shape, diameter and colour, among others. Sensors are some of the tools that you can use for the contact method.

Motion-Step /Sequencing Method: Checks that all the steps involved have been met. An example of motion-step poka yoke is tagging boxes during packaging or completing a checklist to ensure every step has been completed in the process. Checklist can 

Constant Number (or fixed-value) Method: Ensures that a certain number of steps are achieved within a process. This method is suitable for systems that demand high consistency levels. Example counting process to ensure a consistent number of actions are completed in each process.

Poka yoke Regulatory Functions. Which poka-yoke approach? 

Shout Out / Intervention Method: Preventing the error from being made. Stops the process automatically until you address the mistake. If the error is yet to occur, the function requires the process to wait until the conditions are right to proceed.

Attention / Control Function: Highlight that an error has occurred. Sets up warning signals that draw attention to the mistake.

When to Use Poka Yoke

Poka Yoke technique can be used whenever a mistake or error could occur or something done wrong in a business process – meaning everywhere. 

Why fix something when it breaks when you could stop it before it even becomes a problem. Eliminating the points of failure in a process caused by human error. Poka Yokes aim is to guide people to make sure a process works right the first time and every time making sure mistakes never happen.

Proper execution of a poka yoke strategy requires you to identify situations that necessitate it. One is when a step has a high risk of human error that leads to defects and mistakes. 

Concentrate on processes and systems that rely heavily on an employees experience, skill and attention. Another suitable situation is during a hand-off stage when the output, or customer in the case of service processes, has to be transferred to a different employee. Also, look out for instances when an error could be catastrophic or too costly.

Poke Yoke Checklist

The steps you need to take to identify mistakes and implement a fix to stop them from happening again.

  • What is the problem or mistake? Are there high numbers of errors?
  • Where in the process does the problem occur? Identify the process and learn as much about the system as possible.
  • Analyse the process to identify which ways the process can fail.
  • Identify the reason for the mistake? Look for the root cause or use the 5 whys to work out why it is happening.
  • What is the solution to stop the mistake? Implement Poka Yoke approach shut out type or attention type.
    Determine what is most appropriate action a contact (shape or size), constant number ( number of actions needed), or sequencing (using of a checklist to ensure each step in the process is completed).
  • Testing: Is it reducing or eliminate the mistakes in a specific process. Make sure the mistake cannot happen again in the future.
  • Training: Train everyone who works in the process in the new system to use the new poka-yoke procedures

Who can benefit from Poke Yoke

From the service industry to manufacturing to everyday life, poka-yoke is an effective method of reducing errors and consequently, wastage. It allows systems to run more smoothly. For maximum benefits, companies must know when to implement poka yoke and the most suitable approach to take, depending on the circumstances.

Lean Tools used in Poka Yoke

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