MISTAKE PROOFING (POKA YOKE)

Introduction-

Mistake proofing is the easiest way of avoiding waste!

Yes! You heard it right. Proofing can be achieved by awareness, detection and prevention.

1. Awareness- having the foresight that a mistake can be made. Awareness can be spread by training or sharing experience. At the earliest, by communicating and planning the design of the product, process or service to detect or prevent it.

  

2. Detection- some mean to detect mistake and alarm the operators so that it is fixed before product or services are delivered to our customers.

  

3. Prevention- By not allowing the possibility for the mistake to occur at all at any stage of process.

These mistake adversely affects our customer & consumers, our employees and results in waste! There is always a cost associated with defects and such mistakes. So isn’t awareness, detection and or prevention the easiest ways of mistake proofing? Reprimand worker, one-to-one session with boss, retrain worker, warning, asking to be more careful or pay attention were the old ways towards preventing mistakes.

In today’s high technology word a better way to prevent mistakes is to remove the opportunity for error by Improve process and making wrong actions more difficult to accept manually, automatically as well. Or at the most, make easier to discover the errors that do occur in the process so that it is fixed on time.

BACKGROUND-

Dr. Shigeo shingo invented the Japanese concept called poke yoke as a part of the Toyota Production System in 1960s. “Poke” means “Mistake” and “Yoke” means to “Avoid”. The essential idea of poke yoke is to design process in such a way that mistakes are impossible or at least easily detected and is corrected. It’s objective is to achieve Zero Defects.

Poke yoke devices fall into 2 categories-

1.     Prevention  

2.     Detection

Prevention poke yoke -

A prevention device engineers the process so that it is impossible to make mistake at all.

Detection poke yoke -

A detection device engineers the process that detects the error or mistake.

Typical Errors-

• Processing errors
• Missing operation
• Inappropriate procedures
• Missing parts
• Missing information
• Wrong parts
• Damaged materials
• Tools or equipment improperly prepared or setup
• Human errors

Some mistake proofing strategies are like to-

• Make it harder to error to happen.
• Make it possible to reverse the error.
• Detect deviations caused after error.
• Design process so that it tolerates the error and doesn’t result in defect.

Approaches to mistake proofing should be-

1.     Control approach- controls are design that can tolerate variations. They are robust design and have high capability of achieving Zero defects and outliers.

2.     Warning approach- An automatic stop, lights or sound to brings attention to the problem helps the operator to fix it.

Let’s take an example to have an idea on “COST” of mistake proofing-

 Advantages of Mistake proofing are -

 -        Remove defects

-        Faster defect detection and correction

-        Improve safety of workers

-        Improve effectiveness and assures higher reliability of equipment.

-        Ultimately savings in terms of cost on wastes

Few Limitations are that it

• -        Requires special training in terms of equipment knowledge
• -        Requires work culture of 100% vigilance and perfectionism

How one can implement-

• Design the product so that it can’t be assembled incorrectly
• Design process on services that can be delivered in best possible way which gives 100% customer satisfaction.