Mistake Sample

1. 1© 2004 Superfactory™. All Rights Reserved.
Mistake Proofing and Poka YokeMistake Proofing and Poka Yoke
Superfactory Excellence Program™Superfactory Excellence Program™
www.superfactory.comwww.superfactory.com

2. 2
© 2004 Superfactory™. All
Rights Reserved.
OutlineOutline
 What is Mistake Proofing?What is Mistake Proofing?
 Everyday ExamplesEveryday Examples
 Effectiveness & ROIEffectiveness & ROI
 Error Proofing and SPCError Proofing and SPC
 Inspection TechniquesInspection Techniques
 Types of Poka YokesTypes of Poka Yokes

3. 3
© 2004 Superfactory™. All
Rights Reserved.
Everyday ExamplesEveryday Examples
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.
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.
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.

4. 4
© 2004 Superfactory™. All
Rights Reserved.
Poka yoke & SPCPoka yoke & SPC
X-bar chart
(measurement data)
p-chart
(attribute data)
Successive-
checks
or
Self-checks
use to sort out
defects, will not
improve the process
special case of np-
chart,
ad hoc design,
will also sort out
defects
Source-
Inspection
use as corrective
action for special
causes
use to eliminate
specific
types of defects

5. 5
© 2004 Superfactory™. All
Rights Reserved.
Task TypeTask Type ProbabilityProbability
Detection of deviation or inspectionDetection of deviation or inspection 0.070.07
Alpha input per characterAlpha input per character 0.0080.008
Numeric input per characterNumeric input per character 0.0030.003
Assembly per task elementAssembly per task element 0.000070.00007
As a group they areAs a group they are commoncommon
Research study #1 (Harris)Research study #1 (Harris) >0.80>0.80
Research study #2 (Rook)Research study #2 (Rook) 0.820.82
Research study #3 (Voegtlen)Research study #3 (Voegtlen) 0.600.60
Research study #4 (Headlamps)Research study #4 (Headlamps) >0.70>0.70
NASA mishapsNASA mishaps >0.50>0.50
FAA Maintenance problemsFAA Maintenance problems >0.94>0.94
Individually, mistakes areIndividually, mistakes are rarerare
Data from “Human Reliability Data - The State of the Art and the Possibilities”
Jeremy C. Williams, 1989 CEGB

6. 5
© 2004 Superfactory™. All
Rights Reserved.
Task TypeTask Type ProbabilityProbability
Detection of deviation or inspectionDetection of deviation or inspection 0.070.07
Alpha input per characterAlpha input per character 0.0080.008
Numeric input per characterNumeric input per character 0.0030.003
Assembly per task elementAssembly per task element 0.000070.00007
As a group they areAs a group they are commoncommon
Research study #1 (Harris)Research study #1 (Harris) >0.80>0.80
Research study #2 (Rook)Research study #2 (Rook) 0.820.82
Research study #3 (Voegtlen)Research study #3 (Voegtlen) 0.600.60
Research study #4 (Headlamps)Research study #4 (Headlamps) >0.70>0.70
NASA mishapsNASA mishaps >0.50>0.50
FAA Maintenance problemsFAA Maintenance problems >0.94>0.94
Individually, mistakes areIndividually, mistakes are rarerare
Data from “Human Reliability Data - The State of the Art and the Possibilities”
Jeremy C. Williams, 1989 CEGB