1. Poka Yoke & Mistake Proofing
Superfactory Manufacturing Excellence Series
Lean Overview
5S & Visual Factory
Cellular Manufacturing
Jidoka
Kaizen
Poka Yoke & Mistake Proofing
Quick Changeover & SMED
Production Preparation Process (3P)
Pull Manufacturing & Just In Time
Standard Work
Theory of Constraints
Total Productive Maintenance
Training Within Industry (TWI)
Value Streams

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Contents
Introduction
Background and History
Components and Implementation
Knowledge Check
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Introduction
Mistake proofing and poka yoke is the use of process or design features to prevent errors or their negative impact.
The term Poka yoke is Japanese slang for “avoiding inadvertent errors” which was formalized by Shigeo Shingo.
Inexpensive.
Very effective.
Based on simplicity and ingenuity.
© 2007 Superfactory™. All Rights Reserved.

4. Background and History
Shingo suggested a solution that became the first poka yoke device:
In the old method, a worker began by taking two springs out of a large parts box and then assembled a switch.
In the new approach, a small dish is placed in front of the parts box and the worker's first task is to take two springs out of the box and place them on the dish. Then the worker assembles the switch. If any spring remains on the dish, then the worker knows that he or she has forgotten to insert it.
The new procedure completely eliminated the problem of the missing springs.
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5. Components and Implementation
Everyday Examples
Error Proofing and SPC
Inspection Techniques
Types of Poka Yokes
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Everyday Examples
3.5 inch diskettes cannot be inserted unless diskette is oriented correctly. This is as far as a disk can be inserted upside-down. The beveled corner of the diskette along with the fact that the diskette is not square, prohibit incorrect orientation.
Fueling area of car has three error-proofing devices:
1. insert keeps leaded-fuel nozzle from being inserted
2. tether does not allow loss of gas cap
3. gas cap has ratchet to signal proper tightness and
prevent overtightening.
New lawn mowers are required to have a safety bar on the handle that must be pulled back in order to start the engine. If you let go of the safety bar, the mower blade stops in 3 seconds or less.
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7. Everyday Examples: Whose signature is required?
Before:
After:
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8. Ten Types of Human Mistakes
Forgetfulness
Misunderstanding
Wrong identification
Lack of experience
Willful (ignoring rules or procedure)
Inadvertent or sloppiness
Slowliness
Lack of standardization
Surprise (unexpected machine operation, etc.)
Intentional (sabotage)
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3 Rules of Poka Yoke
Don’t wait for the perfect poka yoke. Do it now!
If your poka yoke idea has better than 50% chance to succeed…Do it!
Do it now….improve later!
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