POKA YOKA THE MISTAKE PROOFING

2. What is Poka-Yoke?
• This is known as ‘MISTAKE-PROOFING’
• From Japanese:
• Yokeru (avoid)
• Poka (inadvertent errors)

3. What Does Poka-Yoke Do?
• Eliminates the cause of an error at the
source;
• Detects an error as it is being made;
• Detects an error soon after it has been
made but before it reaches the next
operation.

4. Are Errors Unavoidable?
• There are two approaches to dealing with
errors:
• 1. ERRORS ARE INEVITABLE!
• 2. ERRORS CAN BE ELIMINATED!

5. 1. Errors Are Inevitable
• People always make mistakes.
• While we accept the mistakes as natural, we
blame the people who make them.
• With this attitude, we are likely to overlook
defects as they occur in production.
• They may be detected at final inspection, or
worse still, by the customer.

6. 2. Errors Can Be Eliminated
• Any kind of mistake people make can be
reduced or even eliminated.
• People make fewer mistakes if they are
supported by proper training and by a
production system based on the principle
that errors can be avoided.

7. Inspection
• One method of detecting errors is
inspection.
• There are two major types of inspection.
• 1. SAMPLING INSPECTION.
• 2. 100% INSPECTION.

8. 1.Sampling Inspection
• In some factories, the attitude is:
“It may take all day to inspect all product”.
• “There may be a few defects, but sampling is the most
practical way to check”.
Sampling Inspection - Reflection
• Think about sampling.
• With sampling, there is a chance that an error may go
undetected.
• Even if 1 part in 1000 is defective, the customer who
buys that part has a 100% defective product!

9. Sampling Inspection - Reflection
• Think about sampling.
• With sampling, there is a chance that an error may go
undetected.
• Even if 1 part in 1000 is defective, the customer who
buys that part has a 100% defective product!

10. SAMPLING INSPECTION MAKES SENSE ONLY
FROM THE MANUFACTURER’S VIEW, NOT
FROM THE CUSTOMER’S!
Sampling Inspection - Reflection

11. 2. 100% Inspection
• In the best factories, the attitude is:
• “We won’t tolerate a single defect!”
• “We will organize production so that 100%
of the product can be easily inspected”.
• “That makes the most sense”.

14. The User is Best Inspector

16. Two Strategies for Zero Defects
1. DON’T MAKE IT!
1. Don’t Make It!
 Don’t make product you don’t need.
 The more you make, the greater the opportunity for defects.
 Follow ‘just-in-time’ principles by only making what is
needed, when it is needed in the amount needed.

17. Two Strategies for Zero Defects
2. Build Safeguards
The user is an expert in finding defects.
Therefore build safeguards into the production
process.
Quality can be built into products by implementation
of Poka-Yoke.

18. Poka-Yoke Devices
Human errors are usually inadvertent.
Poka-yoke devices help us avoid
defects, even when inadvertent errors are
made.
Poka-yoke helps build quality into
processes.

19. Poka-Yoke Devices
– Error Detection and Alarms

20. Poka-Yoke Devices
– Checklists

21. Poka-Yoke Example
It is possible to mount the blank the
wrong way onto the pierce tool.
As the blank can fit the pierce tool in
many ways, how can this be prevented?

22. Poka-Yoke Example