Poka Yoke is a tool used in many manufacturing industries to streamline processes and reduce the chance of errors, particularly human error. It’s a form of mistake proofing that not only optimizes production, but optimizes use of finished products as well. That’s because in addition to defect management, Poka Yoke does as much as possible to ensure that products cannot be misused.
What is Poka Yoke?
Poka Yoke is a system of manufacturing that aims to reduce errors and improve efficiency in the production process through a focus on human error. By introducing small changes in the form of quality and operational checks, you can correct defects before they become problems.
The system was developed in the 1960s, when Japanese engineer Shigeo Shingo, who worked for Toyota, developed an exceptional method of ensuring there were zero defects in production. This was called Poka Yoke – Poka Yoke means «error-proof» in Japanese – and it is a technique to avoid simple human errors at work.
The underlying concept is that workers are human beings, not machines, and are therefore going to slip up now and again, especially when working highly repetitive mechanical jobs. Reprimanding them would only lower their motivation and would not do much to resolve the errors, so Shingo decided to create a system based on avoiding errors entirely. This system would integrate seamlessly into existing routines, allowing business to proceed more or less as usual.
How would this be done? By introducing control mechanisms that prevent mistakes before they happen, or make them so apparent that the employee notices and corrects them in time.
When describing the system in his book Zero Quality Control, Shingo outlined three basic principles behind Poka Yoke:
- Mistakes are inevitable, defects in product are not
- A mistake must be detected before it becomes a defect
- The best tool to prevent product defects is one that isolates the source of the problem.
The concept of Poka Yoke is simple: When there are no errors during production, the result will be a high-quality product that does not need revising. Consequently, it lowers costs at the same time and increases customer satisfaction. In addition, not only is the concept simple, the tools and/or devices must be simple..
This is a similar approach to Lean Manufacturing; the Six Sigma approach, and the 5S System which all advocate the enormous potential of keeping your organizational system concise and simple.
What are the types of Poka Yoke?
Before you implement Poka Yoke techniques, be aware that the system involves different types of inspections with different purposes. There are three inspection techniques, and they are:
- Inspections conducted at the source which aim to detect errors where they occur, before they cause defects.
- 100% defect inspection, which involves using sensitive mechanisms, such as a limit switch or warning buzzers, to mistake-proof the process.
- Automatic inspection which use electronic devices that detect errors in the machine.
Any well-designed Poka Yoke inspection will use all three of these inspection types. Poka Yoke processes also perform one of two functions. These are:
Control function:
Mechanisms and devices serving to control the production process warn you of potential failures before they happen. If there was already an error, control mechanisms will halt the production process until the worker has corrected the error. If the error has not happened yet, production will halt until conditions are correct.
Warning function:
Devices that fulfill the warning function of Poka Yoke will simply alert workers to the presence of errors. This is done by using flashing lights, buzzers, bells, or other noticeable signals. Since these devices only let you know an error has occurred, it is up to individual workers to identify and address the problem.
Poka Yoke meaning and methods
The two functions of Poka Yoke illustrate the meaning of the concept; using simple maintenance to ensure a production process that is free of errors. Mistake-proofing your organization is easy once you understand the methodology involved.
There are three Poka-yoke methods used for defect management. These are:
- Contact methods: Contact methods identify defects by inspecting physical attributes, like size, shape, weight, or color.
- Fixed value methods: A fixed-value defect inspection requires that a given movement happen a certain number of times (for example, that a screw be tightened six times) during production, and will alert workers if this has not happened.
- Motion-step method: The motion step method of Poka Yoke inspection is designed to determine if the exact amount of steps required for production have been followed.
However, production experts Richard Chase and Douglas Stewart define a few more types of Poka Yoke in their work Mistake-Proofing: Designing Errors Out. These four new types can be adapted to other markets easily, and they are:
- Physical Poka Yokes: Devices or mechanisms that prevent errors in products and operations by identifying physical anomalies, similar to those examined in contact methods.
- Sequential Poka Yokes: Devices or mechanisms used to ensure that a specific production order or sequence is followed. Making sure workers understand the importance of following each step in sequence is key to quality manufacturing.
- Grouping Poka Yokes: Tools or components pre-arranged in sets, so that it’s easy to tell when a component has been forgotten
- Information Poka Yokes: Mechanisms that immediately inform workers of production status, which update consistently. Nowadays, this is often done using digital reporting tools.
What are the benefits of Poka Yoke?
Poka Yoke is a popular system because it has numerous benefits, even beyond ensuring you end up with high-quality products. This is why it is so widely used by companies today.
As mentioned, it reduces the likelihood of errors in the manufacturing process. This leads to an increase in production quality and incorporates feedback obtained through observation of past errors.
Poka Yoke also saves you time and money, because you will not have to deal with repairing already-made products, or worse, recalling them entirely. By using such a defect management system, you can make fast and effective corrections if something does go wrong.
Mistake proofing improves employee conditions by reducing the need for discipline from supervisors.Avoiding human error also prevents workers from losing motivation every time they make a mistake. Poka Yoke makes work easier and creates a better working environment due to the increased safety of powerful automatic inspections.
Finally, improving your manufacturing process and producing products with fewer defects improves the consumer experience. The principle of reducing human error also applies to final products, which makes goods and services more convenient to use.
What are some Poka Yoke examples?
Even if it’s not apparent at first, Poka Yoke examples are all around us. The subtlety of their presence is an indication of just how smooth Poka Yoke is to implement. Poka Yoke examples can be found in businesses as well as in daily life.
What is Poka Yoke in companies?
There are many common business and manufacturing processes that are excellent examples of Poka Yoke being applied. These include:
- Parts that only fit correctly in one position, connecting components with one specific sequence, or any mechanical device that has to be in a certain position. With only one correct way to assemble a product, any error will be obvious immediately.
- Mechanisms that require an exact number of parts for assembly. These parts are often distributed to workers in individual containers, thus making it easy to track missing components.
- Sensors or control devices that identify the number of tasks and monitor the sequence in manufacturing processes. In case the wrong number or sequence of tasks is performed, an alarm or other warning will trigger.
- Clearly color coding cables and other wiring, to prevent confusion and ensure proper assembly.
What is Poka Yoke in daily life?
Just like production processes are mistake-proof thanks to application of Poka Yoke systems, final products use these principles so that consumers will not misuse or break their purchase. Poka Yoke examples in everyday product use include:
- USB devices which only fit your computer one way, preventing you from accidentally breaking your flash drive or harming the port
- The Microsoft Word prompt which asks if you want to save your document before closing the program, in case you accidentally close it without meaning to
- When you enter an elevator and exceed the weight limit, an alarm will go off and the machine will stop until enough weight is removed
- When you use your computer and it starts to overheat, it will warn you of the problem, Island eventually shut down if you do nothing
- Machines like washing machines and microwaves won’t start until the door is closed and locked
Introducing Poka Yoke to your business is easier than ever now with the variety of digital solutions available, like cloud-based software and apps. With a digital solution like Lumiform, you can easily create checklists and forms that your employees can use to audit their production work and record errors that they observe. Receiving and processing your information is easy because all data is automatically stored, so you can refer back to it when it’s time to further optimize your processes.
The fully paperless and digital app automatically generates reports based on the data you collect, which means you’ll be able to measure the results of your Poka Yoke implementation.
