Poka Yoke

Poka Yoke comes from Japan and was introduced by Shigeo Shingo to Toyota as a part of the production system. The word Poka means ‘inadvertent mistake’ and Yoke means ‘prevention’. It’s not about finding or correcting mistakes in a process but preventing them from ever being made. Poka Yoke is used to design processes so that defects are almost impossible.

The five steps

A Poke Yoke comprises five steps:

• Describe the defect;
• Where is the defect caused? Go and see, go to the Gemba. Gemba means work floor. This is the place where the process is carried out and where the root causes of the defect can be found;
• Analyse the process in which the defect is found;
• What is the underlying reason for the defect? Go and look for that root cause;
• Devise a solution and implement Poka Yoke. Make sure that the defect cannot be made again in the future.

Three TYPES of Poka Yoke

There are three types of Poke Yoke:

• Visual aids: these can be seen and visualise the way of working. It might be a traffic sign, for example, which shows the direction you have to travel.
• Visual management aids: these will ‘signal’ a warning in case of deviation and will thus direct behaviour, an example is a barrier, which stops you from going in a particular direction.
• Failsafe: these will ‘force’ behaviour, for example, there is no another exit to arrive at particular destination.

Frequently Poka Yoke tools

Various Lean tools are used in Poka Yoke:

• Process Mapping: a visual overview of the process within the organisation;
• Five Whys: by asking why five times, you get closer to the heart of the problem and, ultimately, the solution;
• Go to the Gemba: Go to the work floor This is where the processes take place but it is also the defects arise;
• Cause and Effect Diagram: a tool for illustrating problems. It can be used to improve production processes and quality control;
• FMEA (Six Sigma tool): Failure Modes and Effects Analysis. A system that analyses the design of a product or service system and identifies possible errors. Action is then taken to prevent or minimalise them.