Lean Six Sigma Green Belt Certification Poka Yoke

Let us talk about Poka Yoke, a tool widely used in Lean and also now integrated into Lean and Six Sigma implementations. Poka Yoke, also known as mistake-proofing, was coined in the late 60s by Shigeo Shingo who helped design the process and worked as a quality control professional. Earlier it came out to be as Baka-Yoke, which means idiot in Japanese, and later for an inadvertent mistake was termed Poka-Yoke. Sometimes also referred to as idiot-proofing to indicate that a system should be designed such that even fools should not be able to commit a mistake, this topic is easy to understand but requires some guidance.

Poka-yoke is simply a tool that helps you fix as well as prevent inadvertent errors caused by humans such as processing wrong material or workpiece, not following standard practices or procedures or not maintaining equipment. This is one of the most important topics in the Lean Six Sigma Black Belt and needs to be given attention in order to understand it correctly. 

Poka-Yoke- How to solve & tips

There are a total of 12 tips to complete Poka-Yoke correctly. These tips are carefully designed by our industry experts and they are as follows –

• Source of errors could be from equipment and material likely by improper setup, adjustment error, excessive wear, poor maintenance, and overburden and also uneven production could be followed by missing, wrong or defective parts.
• Poka-yoke helps avoid even a simple error in your own workplace. It shows more miraculous results when clubbed with ‘2 second lean’. The idea undertaken is to nullify the repetitive tasks which rely on error and lapses behind the wall of focus. It is one of the common branches of the tree, Zero-Defect Quality Control.
• The main aim of this technique is to reduce the risk of mistakes or errors, minimise the effort required to perform activities, and detect errors prior to them impacting people.
• Ideally, Poka-yoke can be distinguished as prevention-based or detection based.
• In the prevention type, poka-yoke does not allow or have the possibility for the occurrence of any mistake, as it does not allow the process to begin or continue if an error has occurred. Let’s say while inserting a sim-card, the cavity won’t go in unless the sim-card is placed as designed.
• Not all problems or errors can be eliminated but a warning can be provided. Here, poka-yoke allows the error to be but alerts the user to make it right. The only thing to ensure with this poka-yoke is that error is investigated and appropriate actions are taken.
• All mistake-proofing activities fall under one of these three categories: Contact method, Fixed-value method and Motion step method.
• Contact method is based on verification which detects oddity with respect to design or standard and responds back accordingly. Let’s say the orientation of a plate should match with a notch. Locator pins, switches, notches, and fixtures respective to design can help through it here.
• Fixed value method is based on verification of count, value or number of items or else number of events to be followed. Let’s say 15 balls are required to complete a packed box, the same number of shelves in the box shall be made prior, which gives a visual check confirmation.
• Motion sequence method verifies whether layered operation or sequence is followed.

Apart from the above methods, 6 principles are followed by this technique.

1. Elimination (“don’t do it anymore”) is to eliminate the possibility of error by redesigning the product or process so that the task or part is no longer necessary.
2. Prevention (“make sure it can never be done wrong”) is to design and engineer the product or process so that it is impossible to make a mistake at all.
3. Replacement (“use something better”) is to substitute a more reliable process to improve consistency.
4. Facilitation (“make tasks easier to perform”) is employing techniques and to combine steps to make work easier to perform.
5. Detection (“notice what is going wrong and stop it”) is to identify an error before further processing occurs so that the user can quickly correct the problem.
6. Mitigation (“don’t let the situation get too bad”) is to seek to minimise the effects of errors.
7. Elimination, Prevention, Replacement and Facilitation are to avoid the occurrence of mistakes. Detection and Mitigation are to minimise the effects of mistakes once they occur.  

How to implement Poka-Yoke?

• Study the complete process, operation or steps involved in detail, jot down the errors from the sources.
• Use FMEA in the sector you are in to review and analyse the process in an effective manner.
• Use the charter to initiate and keep track by jotting down identified problems, their source, type and area of impact. It can be done for multiple locations, equipment and processes

• Make a matrix of Cause of defect v/s Human error, giving a score to it, one can analyze the priority and type to be implemented.
•  List down the best implementable solution to each. Redesign to eliminate the chances of errors followed by detection type where prevention is not applicable.
• Implement the best method or device for each error.
• Use before-after to document the above. A checklist can be followed to monitor the proper functioning of poka-yoke implemented at a regular duration

•  Poka-yoke has been widely used not only in Japan but in every sector leaving a productive as well as an appreciable mark.
• Some benefits of Poka-Yoke are-
• elimination of set-up errors and improved quality
• decreased set-up times with associated reduction in production time and improved production capacity
• simplified and improved housekeeping
• Increased safety
• lower costs
• lower skill requirements
• increased production flexibility
• Improved operator attitudes.

Lean Six Sigma Green Belt Certification Poka-Yoke example 1

Mistake proofing in Japanese termed as

Lean Six Sigma Green Belt Certification Poka-Yoke example 2

Prevention is __

Lean Six Sigma Green Belt Certification Poka-Yoke example 3

Mitigation is __

Lean Six Sigma Green Belt Certification Poka-Yoke example 4

Detection is __

Answers for skills building exercises

Answer for the first sample exercise is : Poka Yoke, also known as mistake proofing, was coined in the late 60’s by Shigeo Shingo who helped design the process and worked as quality control professional.

Answer for the second sample exercise is : Prevention (“make sure it can never be done wrong”) is to design and engineer the product or process so that it is impossible to make a mistake at all.

Answer for the third sample exercise is : Mitigation (“don’t let the situation get too bad”) is to seek to minimise the effects of errors.

Answer for the fourth sample exercise is : Detection (“notice what is going wrong and stop it”) is to identify an error before further processing occurs so that the user can quickly correct the problem.

Also read: Lean Six Sigma Green Belt Certification Affinity Diagram