Error Proofing
PEOPLE
SUPPORTIVE
PRACTICE
LEAD TIME
REDUCTION
20
KEYS
LEVELING/
SMALL LOT
EMPLOEE
INVOLVEMENT/
WHITE SHIRT
PROCESS
CAPABILITY
SIX SIGMA
Pull
System
SUPPLIER
DEVELOPMENT
Quick
Set-up
TOTAL
PRODUCTIVE
MAINTENANCE
CONTAINER
-IZATION/
TRANSPORTATION
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Error
Proofing
Error
PLANT,
MACHINE,
OFFICE
LAYOUT
WPO
&
VISUAL
MANAGEMENT
1
Error Proofing
Goals
To understand the principles of
ERROR PROOFING, the reasoning
behind it, and the processes of developing Error
Proofing (poka-yoke) devices
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2
Error Proofing
Objectives
Improve quality (reduce PPM & scrap)
Make the processes easier and more capable
Analyze cell for possible Error Proofing
opportunities
Develop Error Proofing devices and ideas
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3
Error Proofing
Error Proofing Is
The process of anticipating,
preventing, & detecting errors which
adversely affect customers & result
in waste
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4
Error Proofing
Questions
Will Error Proofing be more work to
complicate our jobs even further?
How does Error Proofing fit in the AMPS
program?
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Error Proofing
Answer
Error Proofing will make your job easier
and safer!
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Error Proofing
How can the Error Proofing class be used?
Catalyst for improvement
Tool for reaching measurables
Learning device
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Error Proofing
What Measurables does Error Proofing affect?
PPM
Scrap
Process Capability
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Error Proofing
Other Benefits
 Safety Improvements
 Quality Improvements
 Ergonomic Benefits
 Promotes Design for Manufacturing
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Error Proofing
Therefore…
Error Proofing Classes only help us reach
our measurables for the overall goals
established in our 20 Keys.
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Error Proofing
Error Proofing
Think – Quality
Think – Right First Time
Think – Zero Defects
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Error Proofing
Why Error Proofing?
Maintain customer satisfaction
Reduce cost
Ability to maintain Continuous
Improvement production
methods and smaller inventories
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Error Proofing
Why Error Proofing?
 Safety
 Quality
– Scrap
– PPM
– Repairs
13
Error Proofing
Safety Examples
Light curtains
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Error Proofing
Safety Examples
Light curtains
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Error Proofing
Safety Examples
Palm buttons
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Error Proofing
1-100-1000 Rule
If it takes 1 hour to fix a problem where
it occurs, it may take 100 hours
downstream, and it may take 1000 hours
at the customer
What are cost implications?
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Error Proofing
Error Proofing Directly Affects
World Class Benchmarks
•
•
•
•
•
•
•
•
PPM
Scrap
Suggestions per employee
% of suggestions implemented
% of employees on teams
WIP hours
Employees Cross Trained
Supplier Days Inventory
25 or less
Less than 2%
15 per year
85%
100%
Less than 4 hrs.
100%
Less than 4 days
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Error Proofing
Parts Per Million
• PPM of 25
22,000 credit cards will have incorrect
cardholder information on the magnetic strips.
55,000 pieces of mail mishandled each month.
18 unsafe plane landings at O’Hare each year.
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Error Proofing
Parts Per Million
• PPM of 25
$19,000 spent annually on CD’s and
tapes that don’t play.
4,000 checks deducted from the wrong
bank accounts each day
50,000 documents lost by the IRS
each year
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Error Proofing
Parts Per Million
 If 75,000 Total shocks and struts go out the
door per day, then only 1.875 can be
defective to meet the goal of 25 PPM
 When the customer gets that defective shock
or strut, do they care that the other 74,998
were good?
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Error Proofing
Parts Per Million
 If 1000 exhaust systems are produced per
shift. How many defects can we have and still
be at 25 PPM or less? .025
 When the customer gets that defective part or
assembly, do they care that the other 999
were good?
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Error Proofing
3 Zeros
Zero defects
Zero waste
Zero delays
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Error Proofing
Error Proofing
• Error Proofing
1. Simple and inexpensive
2. Automatic, or part of process
3. Placed close to mistake, minimizing
damage
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Error Proofing
Error Proofing
What are some everyday examples?
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Error Proofing
Examples
Cannot start the car without it being in park
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Error Proofing
Examples
Dryer stops when you open the door
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Error Proofing
Examples
Mower stops when you release the handle
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Error Proofing
Inside the Refrigerator
Light goes out when you shut the door
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Error Proofing
Exercise 1
List examples of error proofing in room
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Exercise 1
Error Proofing
List Error Proofing Devices in the Room
Error Proofing is the process of anticipating, preventing, and detecting errors which
adversely affect customers and result in waste.
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1. ______________________________
11. ______________________________
2. ______________________________
12. ______________________________
3. ______________________________
13. ______________________________
4. ______________________________
14. ______________________________
5. ______________________________
15. ______________________________
6. ______________________________
16. ______________________________
7. ______________________________
17. ______________________________
8. ______________________________
18. ______________________________
9. ______________________________
19. ______________________________
10. ______________________________
20. ______________________________
31
Error Proofing
Module 2
Error Proofing Devices
and Defects
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Error Proofing
Error Proofing
 Uses techniques that prevent errors by:
– Designing processes and products that cannot be
incorrectly performed, manufactured, or assembled
– Using devices or inspection techniques that detect errors
during the work process rather than at the end of the
process
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Error Proofing
Error Proofing Devices
Simple and inexpensive devices that are used to
prevent errors about to occur or detect errors
and defects that have occurred.
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Error Proofing
Errors and Defects
 An example of an ERROR would be:
– Loading a part incorrectly in a fixture
 A DEFECT would be:
– if that machine were cycled and a bad
part produced
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Error Proofing
Error Proofing
 Five Manufacturing examples
– Guide pins
– Error detection and alarms
– Limit switches
– Counters
– Checklists
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Error Proofing
Examples
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Guide pins allow only the correct baffle to
be loaded in the press
37
Error Proofing
Examples
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Guide pins are used to check alignment
of the flange.
Error Proofing
Examples
Assembly/Mounting Error
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Error Proofing
Examples
Limit Switch
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Error Proofing
Ten Causes of Errors
Processing omissions
– Leaving out one or more process steps.
Processing errors
– Process operations not performed according to the
standard work procedures.
Error in setting up the work-piece
– Using the wrong tooling or setting machine
adjustments incorrectly for the current product
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Error Proofing
Ten Causes of Errors
Missing parts
– Not all parts included in the assembly, welding, or
other processes
Improper part/item
– Wrong part installed in assembly
Processing wrong work piece
– Wrong part machined
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Error Proofing
Ten Causes of Errors
Operations errors
– Carrying out an operation incorrectly; having the
incorrect revision of a standard process or
specification
Adjustment, measurement, dimension errors
– Errors in machine adjustments, testing measurements
or dimensions of parts and gages
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Error Proofing
Ten Causes of Errors
Errors in equipment maintenance or repair
– Defects caused by incorrect repairs or component
replacement
Errors in preparation of blades, jigs, or tools
– Damaged blades, poorly designed jigs, or wrong tools
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Error Proofing
Five Causes of Human Errors
 New worker
– Not familiar with operation
 Forgetfulness
– Lack of concentration and standards from one part to the next
 Willful errors
– Operator thinks his/her way of doing things is best
 Lack of standards
– No standardization of work implemented
 Surprise errors - equipment
– Equipment failures or wrong setup
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Error Proofing
Traditional Management Cycle
 Error takes place
 A defect occurs as a result
 This information is fed back
 Corrective action is taken
accordingly
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Error Proofing
Traditional Alternatives
 100% Inspection
 SPC
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Error Proofing
Error Proofing
•100% Inspection
-Costly
-Non-Value Added
-Not fail-safe
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Error Proofing
SPC
Good Part
Are These Acceptable?
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Error Proofing
Error Proofing
• 99.9% Good
20,000 incorrect drug prescriptions
will be written in next 12 months
12 babies will be given to the wrong
parents every day
291 pacemaker operations will be
performed incorrectly this year
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Error Proofing
Error Proofing
• 99.9% Good
811,000 faulty rolls of 35mm film will
be loaded this year
268,500 defective tires will be shipped
this year
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Error Proofing
Error Proofing
• So if SPC is not acceptable..
Then?
100% inspection AUTOMATICALLY
ERROR PROOFING
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Error Proofing
Exercise 2
 Existing error proofing
 Possible defects
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Exercise 2
Existing Error Proofing and
Possible Defects
Error Proofing
Existing error proofing and its function:

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________
Areas where defects often occur and what they are:

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________
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Error Proofing
Module 3
Inspection
and Zero Defects
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Error Proofing
Who is the best inspector?
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Error Proofing
YOU
The User
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Error Proofing
Types of Inspection
Self-checking - Before handoff
Joint-inspection - During handoff
Successive check - After handoff
Source inspection - Immediately after mistake,
but before it results in a defect
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Error Proofing
Types of Inspection
 Three Approaches
– Judgment
• Discovers defects after they have happened
– Informative
• Reduces defects but doesn’t prevent them
– Source
• Catches errors before they cause defects
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Error Proofing
Source Inspection
 An error takes place
 Feedback is carried out at error stage
before it becomes a defect
 Corrective action is taken accordingly
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Error Proofing
Source Inspection
1. Source inspection to PREVENT errors
before they cause defects
2. 100% inspection using inexpensive
devices
3. Action to stop operations when defect
is detected
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Error Proofing
The Eight Principles of Basic Improvement For
Error Proofing and Zero Defects
1. Build quality into the processes:
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Error Proofing
The Eight Principles of Basic Improvement For
Error Proofing and Zero Defects
2. All inadvertent errors and defects can be
eliminated:
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Error Proofing
The Eight Principles of Basic Improvement For
Error Proofing and Zero Defects
3. Stop doing it wrong and start doing it rightNOW!
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Error Proofing
The Eight Principles of Basic Improvement For
Error Proofing and Zero Defects
4. Don’t think up excuses, think about how
to do it right:
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Error Proofing
The Eight Principles of Basic Improvement For
Error Proofing and Zero Defects
5. A 60% chance of success is good
enough, Implement your idea NOW!:
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Error Proofing
The Eight Principles of Basic Improvement For
Error Proofing and Zero Defects
6. Mistakes and defects can be reduced to
ZERO when everyone works together to
eliminate them:
•
•
•
Zero defects
Zero waste
Zero delays
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Error Proofing
The Eight Principles of Basic Improvement For
Error Proofing and Zero Defects
7. Ten heads are better than one:
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Error Proofing
The Eight Principles of Basic Improvement For
Error Proofing and Zero Defects
8. Seek out the true cause using
the 8D (disciplines) Process:
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Error Proofing
The 8 Step Problem Solving Process
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Step 1:
Use team approach
Step 2:
Describe the problem
Step 3:
Implement short-term corrective action
Error Proofing
The 8 Step Problem Solving Process
Step 4:
Define and Verify root cause(s)
Step 5:
Implement permanent
corrective action
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Error Proofing
The 8 Step Problem Solving Process
Step 6:
Verify effectiveness of
corrective action
Step 7:
Prevent Recurrence
Step 8:
Congratulate team
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Use Team Approach
Congratulate
the Team
Verify Effectiveness
of Corrective Action
Prevent
Recurrence
Error Proofing
Describe the Problem
8-D
Implement Permanent
Corrective Action
Implement Short-term
Corrective Action
Define and Verify
Root Causes
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Error Proofing
Error Proofing
Operator discovers error
Stops process
Quick fix (authorized by Q.A.)
Submit operational problem
Team formulated
‘Run’ problem through 8D
Arrive at solution
Apply solution
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Error Proofing
Module 4
Error Proofing Devices
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Error Proofing
Which Operations?
 High error potential
 Vital characteristics or damage potential
 Failure history
 Complex operation or much routine detail
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Error Proofing
Developing an Error Proofing Device
 Describe defect, show defect rate, form
prevention team
 Identify location of the defect occurrence
 Detail current standards/operating procedures
where defect was made
 Identify any deviation from standard
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Error Proofing
Developing an Error Proofing Device
 Identify red flag conditions (next slide), 5 whys
error happens, until root problem discovered
 Identify error proofing device required
 Create error proofing device and test for results
 CONTINUALLY IMPROVE
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Error Proofing
Red Flag Conditions
 Adjustments
 Tooling and tooling changes
 Dimensions/ specifications/ critical
conditions
 Many or mixed parts
 Multiple steps
 Infrequent production
 Lack of an effective standard
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Error Proofing
Red Flag Conditions
 Symmetry
 Asymmetry
 Rapid repetition
 High / extremely high volume
 Environmental conditions
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Error Proofing
Methods for Using Error Proofing Devices
 Contact method
 Fixed-value method
 Motion-step method
 Warning method
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Error Proofing
Methods for Using Error Proofing Devices
Contact Methods
Works by detecting whether a product
makes physical or energy contact with
a sensing device
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Error Proofing
Contact Method Example
Guide pins align flange and also make it
impossible to put the flange upside-down
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Error Proofing
Contact Method Example
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Tab aligns opening
84
Error Proofing
Contact Method Example
Notch in aligns flange
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Error Proofing
Contact Method Example
Rubber O-ring centers tubing
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Error Proofing
Contact Method Example
Notch ensures proper seam
alignment for welding
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Error Proofing
Contact Method Example
Notch is visible
showing a correctly
loaded part
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Notch is not visible
showing an incorrectly
loaded part
88
Error Proofing
Contact Method Example
Guide pins align blank for stamping
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Error Proofing
Methods for Using Error Proofing Devices
Fixed-Value Method
Can be used when a fixed number of parts or
operations needs to be performed
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Error Proofing
Fixed Value Method
Counter counts the number of welds made
and lights after six welds
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Error Proofing
Methods for Using Error Proofing Devices
Motion-Step Method
Used to sense whether a motion or step in
the process has been carried out within a
certain expected time
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Error Proofing
Methods for Using Error Proofing Devices
Warning Method
Activate a light, buzzer, etc. to signal
operator of abnormalities
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Error Proofing
Types of Sensing Devices
 Physical contact sensing devices
 Energy sensing devices
 Sensors that detect changes in physical
conditions
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Error Proofing
Types of Sensing Devices
Physical Contact Sensing Devices
Detect the actual presence or lack of
presence of a device or part
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Error Proofing
Physical Contact Sensor
No Part
Part Present
Touch
switch
used
to
sense
that
the
full
length
of
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stock has been fed into the press
96
Error Proofing
Physical Contact Sensor
Contact switch used to detect if a rod is too long
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Error Proofing
Types of Sensing Devices
Energy Sensing Devices
Use energy (photoelectric etc.) to
determine whether an error is
occurring
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Error Proofing
Energy Sensing Devices
 Photoelectric switches
– proper size or color
– passage of an object
– proper supply of parts
– proper feeding of parts
 Beam sensors
 Proximity switches
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Error Proofing
Photoelectric
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Error Proofing
Types of Sensing Devices
Change in Physical Conditions
Detect changes in pressure, temperature,
electrical current, etc.
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Error Proofing
Change in Physical Condition
 Pressure
 Temperature
 Electrical current
 pH
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Error Proofing
Error Proofing – Case Study
Problem 1
Processing Omissions
Problem:
An operator is responsible for drilling six holes.
Sometimes he/she loses count and drills too
few holes.
Suggestions To Improve:
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Error Proofing
Error Proofing – Case Study
Problem 2
Processing Errors
Problem:
In the final assemble/packaging of shocks,
customer part numbers change several times
a day, operators sometimes use the incorrect
component package.
Suggestions To Improve:
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Continuous Improvement Activity Sheet
Team
Line
Facility
Before Improvement
Problem
Implemented Item
After Improvement
Date Submitted
Team Contact
W. O. #
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Error Proofing
Idea #
Date Required
Date Completed
Effect
Champion
Error Proofing
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Error Proofing
Exercise 3
 Brainstorming and proposed solutions
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Error Proofing
Module 5
Tracking and Identification
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Error Proofing
Detailed Description of the Problem
Action Taken
Error Proofing
Date
Completed
Person
Responsible
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DATE &
SHIFT
Total
DIMPLER (4.5)
ROBOT (4.5)
PROJ WELDER (4.5)
GREEN BODY CELL
END CAP (4.5)
PRESS (4.5)
BODY ASS'Y (4.5)
GREEN ROD CELL
OUTER BRKT ASSY'S
(1.5)
CUT ITC TUBE (2.)
BINDERS (15.5)
BAD SEALS (15.5)
SPINNER WELDER
(15.5)
FULL STRUTS (15.5)
COMP HEADS (.30)
INNER CYLINDERS
(.36)
WELDED ROD ASSY'S
(2.6)
PISTON RODS (2.3)
SCRAP
Error Proofing
`
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Error Proofing
Tally Sheets
Hour
1
2
3
4
5
Seam Split
III
II
IIII
II
IIIII
Wrinkles
I
II
I
III
I
Bell Split
I
Tool Marks
I
Off Gauge
Burn Holes
II
II
I
I
III
Porosity
I
Burrs
IIII
ID Incorrect
I
Ding
II
Sub Total
8
7
8
I
II
19
III
I
12
II
I
6
I
6
III
II
I
6
I
9
10
II
I
I
III
II
14
I
I
2
I
6
I
14
12
2
I
9
6
4
9
Total
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Total
5
I
9
9
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Error Proofing
Multiple Counters
Counters are attached to the point of use.
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Error Proofing
Ask “Why” Five Times
Problem:
The Cup won’t fit on the
Tail End of The Tail Pipe.
1. Why?
2. Why is the tab too wide?
3. Why does it flatten out?
4. Why is the temp wrong?
5. Why set improperly?
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Error Proofing
Ask “Why” Five Times
Problem:
The bracket on the
struts will not hold.
1. Why?
2. Why is the weld breaking?
3. Why is the bracket misaligned?
4. Why is the fixture misaligning the bracket?
5. Why is the weld slag built up?
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Error Proofing
B.O.S. Chart
Is a one page chart showing data trends identifying key
factors, tracking projects and monitoring
improvements
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Error Proofing
Why Use The B.O.S. Chart Tool?
 B. O. S. charting is a standard tool used to
support visual control
 One page summary which facilitates
management at a glance
 Ensures real activities are occurring to
improve the areas identified as important to
the company
 Is an excellent communications tool
– to employees
– to management
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Error Proofing
B.O.S. Chart Format
Key Measurable
– Target
– Trend Line
Data Analysis
– Pareto
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Improvement
Activities
Improvement
Tracking
Error Proofing
B.O.S. Key Measurable: PPM
300
Ref #
250
200
1
150
2
100
3
50
4
0
Jan
Feb
Mar
Apr
May
Jun
Actual
Jul
Aug
Sep
Oct
Nov
Dec
Description
Redesign finished goods packaging
Procure new component parts
Resp.
End Date
AM
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JK
containers
Improve weld in process weld
monitoring system
6/30/96
SL
Replace current controller on paint
system
GA
7/24/95
9/20/95
Target
50
40
Ref #
Description
Jan
Mar
May
1
Damaged
Assembly
51
48
45
2
Cracked Casing
20
20
18
20
19
3
Broken Weld
19
17
21
18
1
4
Paint Blister
14
19
18
10
14
30
20
Jul
39
Sept
5
10
0
Damaged Assembly
Broken Weld
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Cracked Casing
Paint blister
Error Proofing
Error Proofing Identification
Description of
Error Proofing
device
P1
Description of
Error Proofing
device
P2
Description of
Error Proofing
device
P3
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Error Proofing
Error Proofing Identification
The “P” symbol shall be approximately 3inches
(75mm) wide and 4 inches (100mm) tall, and
attached on or near the Error Proofing device.
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Error Proofing
Error Proofing Identification
* SOURCE INSPECTION *
P1 Device
(Green)
An Error Proofing device that prevents an error
from occurring
P1
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Error Proofing
Error Proofing Identification
* INFORMATIVE INSPECTION *
P2 Device
(Purple)
An Error Proofing device that detects an error in
time to allow rework before it becomes a defect
and prevents further errors of the same type
P2
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Error Proofing
Error Proofing Identification
* JUDGEMENT INSPECTION *
P3 Device
(Blue)
An Error Proofing device that detects a defect and
eliminates it from the flow of good products
before it reaches the customer.
P3
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Error Proofing
Error Proofing
Of the three types of Error
Proofing devices mentioned,
which is the best one to use?
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Error Proofing
Continuous Improvement
P1
This does not mean that they all have
to be P1’s, a P3 is better than nothing,
but we should continually improve all
of the error proofing devices
* SOURCE INSPECTION *
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Error Proofing
Critical Operations or Points
 Identify where a
– defect is most likely to
occur
– error proofing device is
CRITICAL POINT
(Gray)
needed but has not yet
been developed
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Error Proofing
What happens if an Error Proofing Device
Fails?
 A lot of defective parts could be produced
SCRAP
SCRAP
SCRAP
SCR
SCRAP
SCRAP
SCRAP
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Error Proofing
Maintain the Error Proofing Devices
 Error proofing devices:
– can and do sometimes fail
– need to be checked at the beginning of each
shift
– need to be properly maintained
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Error Proofing
Testing Error Proofing Devices
 Keep safety in mind
 Understand the function of the device and
what it detects
 May need to have a defective part to cycle
and see if defect is detected
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Error Proofing
Exercise 4
 Label error proofing devices and critical
operations
 Implementation plan
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Exercise 4
Error Proofing
Implementation Plan
Begin immediately, including all cell operators
Utilize data from the before condition
Remember 60% is good enough for starters
Activities Week 1:
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Activities Week 2:
Person(s) Responsible
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Activities Week 3:
Person(s) Responsible
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Activities Week 4:
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Person(s) Responsible
Person(s) Responsible
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