Poka-Yoke is the Japanese equivalent to “Mistake Proofing”. It is a common process analysis tool. It aims at nulling out error or makes it immediately obvious once it occurs. By reducing errors, process can

• run more smoothly
• reduce defect rates
• decrease time
• improve quality of life

It is majorly used in the Manufacturing field.

History of Poka Yoke:
It was initially conceptualised by Shigeo Shingo who was employed as an engineer by Toyota. It was originally described as baka-yoke, but as this means "fool-proofing" (or "idiot-proofing") the name was changed to the milder poka-yoke.

Shingo redesigned a process in which factory workers, while assembling a small switch, would often forget to insert the required spring under one of the switch buttons.Shingo redesigned the process of placing the spring in the place holders and so while placing the switch, the spring must be removed from the place holders before being attached and hence error was averted.

Shingo distinguished between the concepts of inevitable human mistakes and defects in the production. Defects occur when the mistakes are allowed to reach the customer. The aim of poka-yoke is to design the process so that mistakes can be detected and corrected immediately, eliminating defects at the source

The Principles of Poka-Yoke:

The image below shows the principles of Mistakeproofing

Elimination: (“don’t do it anymore”)

It is to eliminate the possibility of error by redesigning the product or process so that the task or part is no longer necessary.

Prevention: (“make sure it can never be done wrong”)

It is to design and engineer the product or process so that it is impossible to make a mistake at all.

Replacement: (“use something better”)

It is to substitute a more reliable process to improve consistency.

Facilitation:  (“make tasks easier to perform”)

It is to employ techniques and to combine steps to make work easier to perform.

Detection: (“notice what is going wrong and stop it”)

It is to identify an error before further processing occurs so that the user can quickly correct the problem.

Mitigation: (“don’t let the situation get too bad”)

It is to seek to minimize the effects of errors.

There are three recognised methods of Poka-Yoke namely

• The Contact Method
• The Constant Number(fixed value)
• The Sequence(motion step)

The Contact Method:
The identification of the physical attribute of the part namely size,shape and colour is used here.By correct orientation alone can the part perfectly fit.Eg: At the fuel station there are different size/shaped fuel pump and diesel and petrol cars have different fuel inlet. The diesel pump will not fit into an unleaded petrol inlet. Saving the user from a headache a few kilometres down the road.

The Constant Number:
In this method,a certain number of steps must be done inorder for the process to be completed.Adding or missing a step leads to error.Eg: When assembling a part with some nuts and bolts, the exact number of nuts and bolts required is available to the worker. If any are left over after the worker has assembled the part, a mistake is detected right away because somewhere a bolt is missing from the part.

The Sequence Method:
Here a product to be designed must follow a specific procedure or flow of actions.Eg:Airplane restroom lights switch ON only when the door is locked.

Let us see how we can implement Poka-Yoke in a manufacturing field

• Get the right people together to discuss and review the product and the manufacturing and assembly process.
• Identify and find out sources of defects.
• Review the features of the parts and how they are assembled. A simple change in product design may make a huge difference.
• Have Poka Yoke expert in these conversations.His experienced is valued a lot
• Effectiveness of Poka Yoke technique should be reviewed continuously.
• Continue to maintain and improve the processes and measure the success.

Advantages of Poka-Yoke

• It reduces the defect from about 3% to the Tenth of it
• Cost Effective

While Poka_yoke is effective,it can be a bit tough for physically challenged people as it majorly depends on colour,shape and due to repetitive task mental tracking and muscular efficiency decreases.

References and Further Learning:

• https://www.creativesafetysupply.com/glossary/poka-yoke/
• https://kanbanize.com/lean-management/improvement/what-is-poka-yoke
• https://asq.org/quality-resources/mistake-proofing
• https://www.rnaautomation.com/blog/poka-yoke-in-manufacturing/
• https://www.lbspartners.ie/poka-yoke-three-effective-methods-to-reduce-rework-and-defects/
• https://www.cmc-consultants.com/blog/6-poka-yoke-mistake-proofing-techniques-that-most-factories-overlook