What is Poka Yoke? Defect-free system guide

What is Poka Yoke?

A production system without errors is a dream shared by many businesses and organizations. A utopia, the practice of producing with zero defects and being a global competitor, which, moreover, needs hardly any quality control due to its perfection. The origin of this idea, an ambitious work goal, eventually spurred the creation of Poka Yoke.

It all began in the 1960s, when Japanese engineer Shigeo Shingo, a Toyota worker, developed an exceptional method for committing zero defects in the production phase. This was called Poka Yoke, which means "error-proof" in his native language (avoidance -yokeru- inadvertent mistakes -poka-), a technique to avoid simple human errors at work.

This idea underlined the need to understand that workers are human beings, not machines, and are therefore prone to making mistakes, especially when working highly-mechanical jobs. Reprimanding them would only lower their motivation, so it was necessary to find a way to avoid any failure at all. This would alleviate the repetition of their routines and give value to their intelligence in the industries.

How would this be done? Through mechanisms that prevent mistakes before they happen, or show them so obviously that the employee notices and corrects them in time.

In the main bibliographic reference for the Poka-yoke tool, Zero Quality Control by Shingo; three basic principles were established to comply with this new system:

1. Mistakes are inevitable, defects are not
2. Mistake must be detected before it becomes a defect
3. The best tool to prevent a defect is one that isolates the source of the problem.

Its concept is simple: With no errors on the production line, quality will be high and "rework" will be minimal. 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 has a similar character to Lean Manufacturing/Management, the Six Sigma, or the 5S System which advocate the enormous potential that a simple and well-organised system has behind it.

In this guide you will learn:

1. What is Poka Yoke and its principles

2. Types of Poka Yoke

3. Why use Poka Yoke: Benefits and advantages

4. Examples of Poka Yoke in business and everyday life

5. How to implement Poka Yoke in your company

What are the types of Poka Yoke? Functions and methods

Before implementing Poka Yoke techniques, Shingo distinguishes different inspection methods for conducting a preventive failure study, explained in his acclaimed work:

1. Inspection at source to detect errors where they occur, before they cause defects.
2. 100% defect inspection using a sensitive mechanism, such as a limit switch.
3. Automatic inspection with electronic devices that detect errors in the machine.

Alongside this, it features two functions that encompass the types of Poka Yoke, these are:

Control function:

Mechanisms and devices that warn of a potential failure before it happens. A prediction of errors that will warn the worker and/or stop the machinery. Highly effective function because the intervention is immediate, blocking a manufacturing failure.

Warning function:

Devices that notify of any error or defect in manufacture. It is accepted that the error may occur and is therefore dependent on the attention of an employee. It differs from the previous one in that it only alerts to the possibility of failure, not to the production process.

With this background information, we move on to the Poka-yoke methods which are classified as the following types:

• Contact methods: Identification of irregularities in the finish or dimensions of the part by means of sensitive devices.
• Fixed value method: Inspection of movements in the process, these reveal irregularities if an operation shows instability in the number of operations.
• Step-movement method: Detection of errors in standard movements where operations are performed with predetermined movements.

However, production experts Richard Chase and Douglas Stewart, in their work Mistake-Proofing: Designing Errors Out classified Poka-yokes into four more general types adaptable to other types of markets:

• Physical Poka-yokes: Devices or mechanisms that prevent errors in products and operations by identifying irregularities of a physical nature.
• Sequential poka-yokes: Devices or mechanisms used to ensure and protect a specific order or sequence. Understanding the importance of strict order in the flow as a key to quality manufacturing.
• Grouping poka-yokes: Tools or components pre-arranged in sets, so that no element is forgotten in the manufacturing process
• Information poka-yokes: Mechanisms that immediately inform the worker of the status of the production process, with constant status reports. Nowadays, digital tools are often used for this purpose, like this one.

Why use Poka Yoke: Benefits and advantages

The benefits of Poka-Yoke are numerous and, nowadays, practically all companies carry out this "philosophy"

Firstly, as we have already mentioned, it reduces the likelihood of errors in the manufacturing process. Therefore, it increases the quality in every corner of production, and adds the feedback obtained by knowing the errors or possible defects.

Eliminates post-flow manufacturing controls, as errors are strictly controlled, thus saving time and money. It also avoids inspection or repair losses. And, in the event that something does happen, it provides a fast and effective correction system.

From a more employee-centric perspective, human error is avoided, thus avoiding supervisor-worker relationship problems, psychological impact and motivational instability. In addition, it makes work easier with its simple mechanism perspective and allows for a better working environment due to the increased safety of the powerful automatic inspection.

By having a better manufacturing process, fewer defects and more productive employees, it improves the user experience for consumers. Not forgetting, either, that this technique is also applied to final products, in order to make the use of goods/services more convenient. In short, it provides a market differentiation and customer approach.

Examples of Poka Yoke in companies and everyday life

Even if we don't realise it, Poka Yoke techniques are very present in our daily lives. Once you understand the concept, you realise how important the Japanese engineer's intellectual contribution has been. These are seen in business as well as in everyday situations.

Examples of Poka Yoke in companies

• Parts that can only fit in a specific position to be correct, connectors of all kinds with a certain polarity or sequence of contacts. This system also applies to any mechanical device that has to be in a certain position. You notice the obviousness of the error as soon as it occurs.
• Mechanisms that require an exact number of parts for assembly. The operator receives the differentiated parts in individual containers, thus highlighting the fault if not all components have been used.
• Sensors or control devices that identify the number of operations and monitor the sequence in manufacturing processes. In the event of an error, an alarm warns of the problem.
• Clear colour coding of cable usage, prevention of process start-up if safety doors are not closed, etc... Basically, strict detectors for every detail and factor in the processes to make everything easy and orderly.

Examples of Poka Yoke in everyday life

• Every time you insert a flash drive, it doesn't fit the first time? There you have the most common Poka Yoke of our times, the USB device that only goes in one way
• Don't close your Word document quickly without thinking, you might lose it! Fortunately, the developers included a reminder that asks if you want to save it before closing the program.
• When you enter a modern lift and exceed the weight limit, an alarm will go off and you will be prevented from using the elevator. Someone will have to wait!
• If you use your computer at an excessive temperature, it will probably alert you to the problem. In case you exceed the maximum, it will automatically shut down.
• Let's not forget our life partners, the washing machine and the microwave. Until you have closed the door, they will not start their mission.

How to implement Poka Yoke System in your company: App/Software

Bearing in mind the importance and effectiveness of applying this method in an organisation, it is highly recommended that Poka Yoke mechanisms are integrated to ensure quality and effectiveness.

Thanks to the technological advancement of our times, there are numerous options that cover the functions of control and warning for little money, offering great benefits. The use of Apps and monitoring software is a simple and efficient way to do this.

At Lumiform we have set out to create an app, with state-of-the-art German technology, that allows your employees to confirm all their steps through checklists and digital forms.

Your operators can check that all machinery is under control with this method, which is fully editable and customisable to any sector. Whether receiving your information, or using existing control templates, the production flow will be well monitored step by step.

Every corner of your organisation can be monitored remotely and, should the slightest error occur, it will be communicated instantly and you can block the production flow in a second.

Alongside all this, the Lumiform App/Software allows you to generate real-time data on your processes to measure quality and safety, giving you a starting point for continuous improvement.

It also automatically generates reports on the results of the controls performed. As a result, you save money and time by reducing defects, getting to know your company better every day.

And finally, it helps you to forget the old-fashioned use of paper and excel for the organisation of your company or business, giving you a step ahead of your competitors with innovative technology and a consistent and intuitive process.