What is Poka Yoke? How to apply Defect Prevention in production

After understanding that these simple human errors were the root cause of all problems, Shingo set out to find ways to improve the process and make the process "Poka Yoke" - meaning error-stopping.

Shingo has redesigned the process so that any operation cannot resume until workers spring into the switch. This has resulted in fewer human errors in the manufacturing process and better quality products.

1. What is Poka Yoke?

"Poka Yoke" is a Japanese term that means "error prevention" or "automatic error prevention". Poka Yoke was developed by management consultant Shigeo Shingo as part of Toyota's production system. The purpose of Poka Yoke is to help produce better quality products and reduce risks in the production process.

A simple example of a Poka Yoke is a car door lock system. This system prevents users from locking the car door while the key is still in the vehicle. Poka Yoke applied in this case is a sensor detection mechanism to signal to the user if the key is still in the car before they lock the door. ​

This helps to avoid cases where the user loses the key or locks the car door with the key in the car, thereby minimizing possible inconvenience situations.

2. Poka Yoke's function and role in production

Poka Yoke is an advanced production tool trusted by many line factories because of the following three functions.

• Fault detection: No matter how superior a human or a machine is, there will be errors in the production or operation process. At this moment, the Poka Yoke system will detect the error and stop the production activities, then notify the management department to review and fix the problem.
• Troubleshooting: In addition to being able to detect errors, Poka Yoke also helps businesses solve minor errors without anyone else's intervention. This helps optimize operating time and use this time to handle other important tasks.​
• Error prevention: In the production line, if there is a small error, the other steps will also go wrong. With Poka Yoke, these defects are detected and production is stopped immediately. Since then, line errors are also prevented in time, without adversely affecting the production process.​

With the above functions, Poka Yoke plays a very important role in the business in general and the production process in particular:

• Reduce production costs : During the production process Poka Yoke will detect and prevent defective processes or products. Since then, this method helps to increase product quality and improve the repair or disposal costs of defective products.
• Reduced management time: Because Poka Yoke has prevented the risk of defects in the present and other errors from recurring in the future, businesses will not need to spend too much time managing the production process. production while maintaining product quality.
• Increase the reputation of the business: Poka Yoke helps the production process of the enterprise to make fewer mistakes, from which the defective products are also less, creating the quality of the product. And from here, the position of the business in the eyes of partners has increased when it is able to produce large volumes of goods, but there are very few defective products.

3. 6 principles of the Poka Yoke error prevention principle

Poka Yoke prevents errors by relying on the following principles:

• Elimination: The act of redesigning a product or process to eliminate defects that have arisen in the manufacturing process.
• Prevention: The design and innovation of a product or process so that potentially fatal errors do not occur.
• Replacement: The replacement of a rule or procedure that is more suitable, less error prone than the old process so as not to repeat the mistakes that have already occurred.
• Facilitation (Convenience): Is the act of using new techniques more effectively to integrate into the production process, thereby creating convenience, improving efficiency and working efficiency.
• Detection: Is the act of detecting and confirming errors and then notifying the manufacturer, helping them quickly fix the problem.
• Mitigation is the action of preventing or stopping production activities if a process fails, minimizing the negative effects of the defect on the production process.

4. When to apply Poka Yoke?​

Poka Yoke can be used whenever a problem or error occurs. Poka Yoke is error-proof, so you can apply it to any situation in the manufacturing or service industry.

However, businesses as well as managers need to answer the following questions:​

• Is the value of the product the business is producing high?
• If there is an error in the production process, how does this error affect the operation process as well as the operating personnel?
• If the product is defective, will it pose a risk as well as danger to the user?

If the above risks are low, enterprises do not need to deploy Poka Yoke. For example, with a straw manufacturing business, the production cost of straws as well as the risk for users is very small or nonexistent, so we will not need to apply the too complicated or expensive Poka Yoke method. .

Some cases where businesses should apply Poka Yoke such as:

• Products with high precision and strict safety requirements, such as in the automotive and electronic equipment manufacturing industries;
• When the production process has risks leading to errors such as machine setting, product packaging;
• Routine work to be performed, which needs high attention to avoid repeated errors.
• Errors related to operating procedures, or production steps that do not follow standard operating procedures;
• Failure to machine equipment is not set up, adjusted or operated improperly.
• Product defects do not meet quality requirements, errors occur in the production process.

5. How to apply Poka Yoke in production

To apply Poka Yoke in production, readers need to follow these steps:

Step 1: Identify the problem

The first step in Poka Yoke is to identify a potential problem or error that may arise in the production process or the employee's workflow. Identifying the problem will help us better understand the causes of the error and find a solution.

You will need to observe the process to see if you can pinpoint where the problem is occurring and determine if the error is man-made or machine-made.

Step 2: Find the root cause

Once you've identified the problem, you'll need to determine what the most likely cause of it is. You might consider using 5 Whys - a deep-rooted digging tool developed in Japan. By asking and answering the five questions in the “5 Whys” method, the producer will be able to dig deep to find the root cause of the problem.

Step 3: Determine the Poka Yoke method to apply

The Poka Yoke error detection system works based on three main methods:

• Contact Method - (Physical contact method): This method checks physical properties such as shape, size, color, or other physical properties to identify errors. Example: We cannot stick a square peg into a round hole.
• Constant number: The product must ensure the correct number of movements, or the correct number of parts/components attached to the product. If this requirement is not met, the system will automatically warn the operator through the system of sensors.
• Sequence: According to this method, the steps in the production process will be arranged in a certain order to limit errors.

You need to determine and select the right Poka Yoke method depending on the defect and the situation as well as the production process.

Step 4: Test, test run

Before officially applying Poka Yoke, you need to make sure that this method works stably. We need to check to see if the bug is prevented and to make sure that the new fix doesn't slow down production in general.

Step 5: Train employees

Even the simplest Poka Yoke cannot be successfully performed if the staff does not know how to do it. Training helps employees adopt new processes more efficiently and accurately.

Step 6: Check the effect

Test the effectiveness of the Poka Yoke through each stage of the production process and modify (if necessary) to optimize the results