Error Proofing.ppt

ERROR PROOFING TECHNIQUES
AGENDA
 OPENING COMMENTS & INTRODUCTIONS
 ERROR PROOFING OVERVIEW
 WORKSHOP EXPECTATIONS - Why Are We Here Problem
Statement
 DEFINE CURRENT STATE
 ERROR PROOFING AWARENESS & TECHNIQUES
 BRAINSTORMING - Problem Solving Solutions Utilizing
Error Proofing Techniques
 DEVELOP ACTION PLANS & IMPLEMENTATION
 CLOSING & WRAP-UP

QUALITY STEP CHART
ACTION PLANS WITH
ACTUAL OR EST. RESULTS
TARGET
TIME
QUALITY MEASURE
Current
State
Improved
Processing = 140 ppm
Reduced
Handling = 120 ppm
Visual
Management = 100 ppm
Error
Proofing = 80 ppm
Preventative
Maintenance = 60 ppm
TIME FRAME OF
ACTION PLANS
INCIDENTS PER
PART OR PPM
ABC Company - Widget Assemblies
SAMPLE CHART
© Copyright General Motors. All rights reserved.

Process
• PROCESS FLOW & DATA WORKSHEETS
• QUALITY RESULTS
• PROCESS MEASURES
• PROBLEM DEFINITION
PROJECT
SELECTION
• CUSTOMER QUALITY CONCERN
• HIGH RPPM / REPEAT PR/R’s
• PART IN CONTROLLED SHIPPING
• CHRONIC QUALITY PROBLEM
• HIGH WARRANTY IMPACT
• HIGH COST OF QUALITY
SELECT
TEAM MEMBERS
• GM PRODUCT/PROCESS ENGINEER
• SUPPLIER PERSONNEL (ENGR., MFG,
QUALITY, OPERATORS, ETC)
• PURCHASING
• SUPPLIER QUALITY ENGINEER
• CUSTOMER REPRESENTATIVE
IDENTIFY
POSSIBLE
CAUSES
• BRAINSTORMING
• 5 WHY’s
• CAUSE & EFFECT DIAGRAM
• STORYBOARD
• COLLECT THE DATA
• RUN CHARTS
• FREQUENCY DISTRIBUTION
• PICTOGRAPH
• SCATTER DIAGRAMS
• PROCESS CAPABILITY STUDY
• DESIGN OF EXPERIMENTS
• PROCESS DISSECTION
ANALYZE THE DATA
SELECT GOOD IDEAS
• GATHER NEW DATA AS NECESSARY.
• DEVELOP ACTION PLANS FOR CONTAINMENT,
CORRECTION, AND PREVENTION.
• DOCUMENT RECOMMENDED CHANGES AND
ACTION PLANS.
• ESTABLISH IMPLEMENTATION TIMING AND
RESPONSIBILITY.
PLAN & IMPLEMENT
CORRECTIVE ACTION
• BASED ON PROFOUND KNOWLEDGE
• OVERCOMING ROADBLOCKS
• ACTION PLANS PROCESSED ASAP
LOOK FOR NEW
OPPORTUNITIES
RECOGNIZE
EFFORTS OF
PEOPLE
EVALUATE
AND ADJUST
• EVALUATE EFFECTIVENESS OF THE
ACTION PLANS.
• MEDIAN & RANGE CHARTS
• AVERAGE & RANGE CHARTS
• PROCESS CAPABILITY
OPERATION:
FROM:___________________________ QUANTITY PER SHIFT:______________ CUSTOMER CYCLE TIME:__________________
TO: _____________________________ SHIFT:________ OPERATOR CYCLE TIME:__________________
DESCRIPTION OF ELEMENT TIME STANDARD IN- QUALITY CRITICAL
NO. OPERATION HAND W ORK
MACHINE
W ALK PROCESS STOCK CHECK OPERATION
SAFETY
WORKSTATION AREA DRAWN TO SCALE
C
Q
03/23/94
1
2
3
4
5
MAKE ALL PEOPLE
AFFECTED AWARE
OF WHAT IS
GOING TO HAPPEN
DEFINE
CURRENT
SITUATION

WHAT IS AN ERROR???
• Errors are inadvertent, unintentional,
accidental mistakes made by people because
of the human sensitivity designed into our
products and processes
• Errors result in those “once in a while”
defects that we always find difficult to
control

Inadvertent errors are not
only possible but inevitable.

EXAMPLES OF ERRORS AT HOME . . .
• Running out of gas
• Locking keys in your car
• Forgetting to stop
• Forgetting to turn off the coffee
pot
• Forgetting to unplug the iron

What if you had to write your name 1500
times every day?
With all of life’s distractions......
Are you 100% sure that you would never
make a mistake?!!!!

EXAMPLES OF ERRORS AT WORK . . .
• Missing Parts
– Forgetting to assemble a part - screws, labels, orifice tubes...
• Misassembled Parts
– Misassembly - loose parts, upside down, not aligned
e.g. - brackets (backwards), seals (not aligned),
screws (loose), labels (upside down), ...
• Incorrect Processing
– Disposing of a part rejected at test to the wrong pile
• Incorrect Parts
– Retrieving and assembling the wrong part from a model mix selection -
seals, labels, brackets, cases...

WHAT ABOUT ERRORS AT WORK?
Mistakes = Lost Time, Lost Money,
and
possibly Lost
Business!!!!
INJURIES

PROBLEM SELECTION CRITERIA
• High Parts per Million
• High PR/R Frequency
• Chronic Quality Problem
• High Cost of Quality
• PFMEA Identified Areas
• High Warranty Cost

EFFECTS OF PROBLEM
CUSTOMER SUPPLIER

WHY DO HUMAN
ERRORS OCCUR
WHEN EVERYONE
IS FOR QUALITY?

WHY DO ERRORS
HAPPEN?
The quality of an operator dependent process is affected by the:
Knowledge (Skill)
Vigilance (Attention to detail)
An operator must have knowledge of the job in order to know
what to do and when a quality part has been produced
In addition, a knowledgeable operator may have to be vigilant
with each part produced to be sure it meets all the quality
expectations
Operator

KNOWLEDGE AND
VIGILANCE
I may be an expert at driving
a car (KNOWLEDGE)
BUT.....
Occasionally, I lock my keys
in the car or run out of gas
(LACK OF VIGILANCE!!!)
EXAMPLE:

People Variation
Rotation
Overtime
Coverage
Shift-Shift
Relief Breaks
Transfers
Farm-Ins
Various People Doing Only One Job!!!!
Various:
 Levels of Training
 Knowledge of Total Product
 Knowledge of Customer Requirements
 Methods of Performing Job

People Variation
KNOWLEDGE
Rotation
Overtime
Coverage
Shift-Shift
Relief Breaks
Transfers
Farm-Ins
Various People Doing Only One Job!!!!
Various:
 Levels of Training
 Knowledge of Total Product
 Knowledge of Customer Requirements
 Methods of Performing Job

OOPS!!!!!!
This is how this job goes...
What are you doing tonight?
What do you think of this new design?
Boredom
Break time!!!
Machine’s down...
Overtime tonight?
There’s a problem with the parts you’re making....
People Distractions

People Distractions
VIGILANCE
OOPS!!!!!!
This is how this job goes...
What are you doing tonight?
What do you think of this new design?
Boredom
Break time!!!
Machine’s down...
Overtime tonight?
There’s a problem with the parts you’re making....

WHY ARE MISTAKES A PROBLEM?
Cost us money
Cost us time
Cause us danger/possible injury

THINGS DONE RIGHT 99.9% OF
THE TIME MEANS . . .
• One hour of unsafe drinking water per month
• Two unsafe landings at O’Hare Airport each day
• 16,000 lost pieces of mail per hour
• 20,000 incorrect drug prescriptions per year
• 500 incorrect surgical operations per week
• 50 newborn babies dropped each day by doctors
• 22,000 checks per hour deducted from wrong accounts
• 32,000 missed heartbeats per person each year

THE ERROR PROOFING
ATTITUDE
• People CAN and WILL make inadvertent
mistakes!
• If one person makes a mistake - ANYONE
can!
• ONE mistake out the door is too many!!
• Mistakes CAN be eliminated and MUST be
eliminated for us to become
COMPETITIVE!!!!

WHAT DO WE DO?
By designing our products and processes
so that they minimize the opportunity
for the mistake to happen in the first place
This is where the concept of
ERROR PROOFING
comes in.......
If errors are so easy to make, how will we ever
send our customers 100% good product?????

A SYSTEM IS NEEDED
TO COMBAT THESE DRAWBACKS:
• Detect an error in the process before a defective
product is passed to the next station; whenever
possible before a defective product is produced.
• Perform detection and notification of operator
immediately; i.e. for every unit of product.

BENEFITS
Assures 1st Piece Quality
Assures Consistency during Set-Ups
Prevents Production of Defective Parts
Makes Quality Problems More Visible
Creates a Safer Work Environment
Eliminates Waste of Inspection and Repair
Lowers Cost of Design (DFM) and Cost to
Manufacture (Poka-Yoke Devices)

To improve the PROCESS by helping
people prevent ERRORS and increase the
chances of DETECTION, so that FAILURE
MODE occurrences are
ELIMINATED.
OBJECTIVE

• INTRODUCTIONS / OPENING COMMENTS.
• OVERVIEW OF SITE OPERATIONS AND DISCUSSION OF
PROBLEM AREA(S).
• WORKSITE REVIEW TO ASSESS PROBLEM AREA FOCUS
AND ISSUES.
• OVERVIEW OF WORKSHOP PROCESS AND ACTIVITIES.
• PRE-WORKSHOP PREPARATION REQUIREMENTS.
• GENERAL DISCUSSION AND ADJOURN.

Agenda
 OPENING COMMENTS & INTRODUCTIONS
 ERROR PROOFING OVERVIEW
 WORKSHOP EXPECTATIONS - Why Are We Here Problem
Statement
 DEFINE CURRENT STATE
 ERROR PROOFING AWARENESS & TECHNIQUES
 BRAINSTORMING - Problem Solving Solutions Utilizing
 DEVELOP ACTION PLANS & IMPLEMENTATION
 CLOSING & WRAP-UP

WHY ARE MISTAKES A PROBLEM?
 Cost us money
 Cost us time
 Cause us danger/possible injury

THE ERROR PROOFING ATTITUDE
 People CAN and WILL make inadvertent mistakes!
 If one person makes a mistake - ANYONE can!
 ONE mistake out the door is too many!!
 Mistakes CAN be eliminated and MUST be eliminated for
us to become COMPETITIVE!!!!

Awareness: Having the forethought that a mistake can be made, communicating the potential, and
planning the design of the product or process to detect or prevent it.
Detection: Allowing the mistake to happen but providing some means of detecting it and alerting
someone so that we fix it before sending it to our customer.
Prevention: Not allowing the possibility for the mistake to occur in the first place.
Error Proofing is the activity of awareness, detection, and
prevention of errors which adversely affect:
Our customers (defects)
Our people (injuries)
and result in WASTE!
WHAT IS ERROR PROOFING?

Techniques
• Design for Manufacturability
• “Poka-Yoke” System Devices
ERROR PROOFING

Techniques:
• Design For Manufacturability (DFM)
Technique that Results in Designs that Cannot
be Incorrectly Manufactured or Assembled.
This Technique can also be used to “Simplify”
the Design and therefore reduce its cost.
ERROR PROOFING

Techniques (Continued)
• “Poka-Yoke” System*
Set-Up Devices or Inspection Techniques that Assure that
Set-Up is Done Correctly; i.e. Produces 100% Good Parts
from the First Piece on
“Zero Quality Control: Source Inspection and the Poka-Yoke System” - Shigeo Shingo; 1986
ERROR PROOFING

 Missing Parts
 Forgetting to assemble a part - screws, labels, orifice tubes...
 Misassembled Parts
 Misassembly - loose parts, upside down, not aligned
 Incorrect Processing
 Disposing of a part rejected at test to the wrong pile
 Incorrect Parts
 Retrieving and assembling the wrong part from a model mix selection -

Identify Error Proofing Opportunities
• PFMEA
• Quality Data, PR/R, Warranty Data...
• Brainstorm (Questions to Ask, Free Form...)
Prioritize Opportunities (RPN, Pareto...)
Determine Level of Error Proofing
Brainstorm Error Proofing Mechanisms
• Build on past experience
• Can use more than one mechanism
Select Error Proofing Mechanism
• Most cost effective
• Simple
Plan (Process Mechanisms)
• Action plan
• Error Proofing Control Plan (EPCP)
Implement Error Proofing Mechanism
•Installation
•Validation
• EPCP
•Check sheet/Log
•Operator Instructions
Evaluate Results
IDENTIFY
PLAN
ANALYZE
IMPLEMENT
EVALUATE
HOW
TO
ERROR
PROOF

TOOLS FOR ANALYSIS
Flow Chart Fishbone Diagram Pareto Chart
Histogram 5 Why’s Run Chart
Scatter Plot Control Chart Pictograph
Problem
Problem
Root Cause
Why
Why
Why
Why
Why

Assures 1st Piece Quality
Assures Consistency during Set-Ups
Prevents Production of Defective Parts
Makes Quality Problems More Visible
Creates a Safer Work Environment
Eliminates Waste of Inspection and Repair
Lowers Cost of Design (DFM) and Cost to
Manufacture (Poka-Yoke Devices)
BENEFITS

ERROR-PROOFING TECHNIQUES
(Poka-Yoke) CONCEPT
SENSOR INFORMATION:
BASIC TYPES OF SENSORS
• Discrete sensors
• Analog sensors
TYPES OF PRESENCE SENSORS
• Physical contact
• No physical contact
TYPES OF NON-CONTACT SENSORS
• Reed relays
• Inductive
• Capacitive
• Photoelectric sensors
ADVANTAGES OF THE VARIOUS TYPES
• Functionality
• Costs
• Areas of application

(Poka-Yoke) CONCEPT
BASIC TYPES OF SENSORS:
ANALOG SENSORS
• Answer the question: “Where is the part?”
or
• “To what level have we filled the container?”
DISCRETE SENSORS
• The part is present or is not present.
• Most frequently asked question in a manufacturing
operation.

(Poka-Yoke) CONCEPT
TYPES OF PRESENCE SENSORS:
PHYSICAL CONTACT
• e.g. Limit switches
• Advantages - Can carry more current
- Gap between terminals
NO PHYSICAL CONTACT
• Advantages - No physical contact
- Better for counting sensitive surfaces,
e.g. painted or polished surfaces
- No moving parts
- Faster

(Poka-Yoke) CONCEPT
TYPES OF NON-CONTACT SENSORS:
REED RELAYS
• Target is magnetic
• Will not respond to non-magnetic targets
with reliability.
INDUCTIVE
• Based on metal targets; will not respond
to non-metallic targets with high reliability.
CAPACITIVE
• Cannot distinguish between the real target
and something else in the target region.
Must control what comes close to the target.
PHOTOELECTRIC
• Can be fooled by a non-target.

(Poka-Yoke) CONCEPT
REED RELAYS
Typical range: Up to 1.5 in. (approx. 4 cm)
• Two hermetically sealed metal foil reeds which make contact
with each other to close the circuit, when in the vicinity of a
magnet (permanent or electro-magnet).
• The differential is determined by differencing the point of first
contact from the point of last contact.
• Magnet approach must be in a direction parallel to the direction
of the line connecting the tow reeds.
Best applications for magnetically actuated switches in general:
• Security and safety
• to avoid false tripping
• security door interlock for heavy machinery; end of travel
for elevators, cranes, and the like.
• Sensing through walls (non-ferrous, e.g. Aluminum and
Magnesium).
• Pallet identification in synchronous automated assembly lines.
• Relative dirty environments (e.g. dust, dirt, sand, oil, or coolant
fluids).
• Whenever high response speeds are required.
Disadvantages - poor long-term reliability (moving parts)

(Poka-Yoke) CONCEPT
INDUCTIVE SENSORS
• Principle of Operation:
• Eddy currents are induced in the target (metallic)
by the electromagnetic.
• The target reacts with the Eddy currents as a
function of the distance from the field.
• Inside the field, the target attenuates the magnitude
of the Eddy currents.
• Outside the field, the target does not impede the
Eddy currents.
• This type of oscillator is referred to as a ECKO
(Eddy Current Killed Oscillator).

(Poka-Yoke) CONCEPT
CAPACITIVE SENSORS
• Principle of Operation:
• Senses all materials
• Contain a high frequency oscillator with one of its
capacitor plates built into the sensor.
• Method of Application:
• All materials are sensed through a change on the
dielectric characteristics.
• Ideal applications include bulk materials and liquids
in containers of glass and plastic.
• Characteristics:
• Poor choice for metal targets.
• Is very sensitive to environmental factors.
• Sensing range depends greatly on the material being
sensed.
• Can be misled and therefore it is important to control
the material which is presented to the sensor.

(Poka-Yoke) CONCEPT
PHOTOELECTRIC SENSORS
Photoelectric controls need no physical contact and are ideal where sensed
objects must remain untouched. Photoelectric controls respond rapidly to
parts moving quickly and in varying positions along a conveyor, yet operate
dependably if actuated only infrequently. There are controls for indoor or
outdoor use, for varying ambient light conditions, for high vibration, for areas
restrictive in space, and even for explosive locations.
Typical applications include:
• Counting
• Labeling
• Conveyor control
• Bin level control
• Parts inspection
• Feed and/or fill control
• Package handling
• Thread break detection
• Edge guide
• Web break detection
• Regristration control
• Food processing
• Parts monitoring and sorting
• Batch counting
• Robotics
• Parts handling

(Poka-Yoke) CONCEPT
Conveyor Control
This application involves sorting brown cardboard boxes which are coded with up to four black marks per
box. The application is to sense the number of marks on each box.
Package Handling
A diffuse scan photoelectric control is used to detect the light reflected from the object in this application.
The control detects the light reflected off the box, turning ON and OFF the gluing machine.
Labeling
This application is designed to detect the leading edge of a black bar code on a read and write label. The
labels are edge to edge on a spool. When the bar code is detected the sensor output triggers a laser bar
code reader which reads the bar code.
Food Processing
This application monitors the level of an accumulator in a meat processing facility. A photoelectric control
detects a fill level of hot-dogs in the accumulator then turns on the conveyor for a preset time period. Side
walls of the accumulator are polished stainless steel. The equipment is subject to daily washdown.
Fill Level Control
This application inspects the fill level of various jars of food products. The photoelectric system produces
an output when either an under or over fill condition is detected.
Parts Handling
Fiber optics are ideal for areas too small for a standard photoelectric control. The fiber optic cables direct
the light from the base to where the sensing is needed.

Target
Thru:
• Light source (emitter) and
receiver are placed opposite
each other.
• The object to be detected passes
between the two.
Advantages:
1. Most reliable when target is opaque
2. Long range scanning, most excess gain
3. Use in high contamination areas, dirt, mist,
condensation, oil film, etc.
4. Precise positioning or edge-guiding of opaque
material
5. Parts counting
Types of Non-Contact Sensors
Photoelectric Sensors
Emitter Receiver
THRU
(Poka-Yoke) CONCEPT

(Poka-Yoke) CONCEPT
Diffuse:
• Light beam is directed at the
object to be detected.
• Light will be reflected off the
object in many directions.
• Some of the light reflected from
the object will be sensed by the
receiver.
Advantages:
1. No reflector required.
2. Convenient for installation.
3. One sided scanning.
4. Senses clear materials when
distance is not fixed.
5. Ease of alignment
Target

(Poka-Yoke) CONCEPT
Proximity (diffuse) Background Suppression
Background suppression utilizes 2 receivers behind the receiving lens. They are
aimed at a precise point in front of the unit and sense the presence of a target
when the output of both receives are equal.
Applications:
• Material handling - conveying systems
• Collision detection for AGV’s (Automatic Guided Vehicles)
• Car / truck wash
• Level sensing

Retroreflective:
• Light beam is directed at a reflective target
(reflector, tape or other reflective object) -
one which returns light along the same
path it was sent.
• The object to be detected passes between
photoelectric control and reflective target.
Advantages:
1. One-sided scanning
3. Immune to vibration
Target
Retroreflective
Reflector
(Poka-Yoke) CONCEPT

Convergent:
• Light beam is directed at object to be
detected (ignores background
surfaces)
• Object must be at a given distance in
relationship to photoelectric control
before light will be reflected to receiver
Advantages:
1. First choice for detecting clear
materials
2. Ignores unwanted background
surface reflection
3. Detects objects with low reflectivity
4. Detects height differential
Target
Convergent Beam
Fixed
Distance
(Poka-Yoke) CONCEPT

(Poka-Yoke) CONCEPT
Fiber Optic Sensors
What do you do when the physical constraints of the application don’t allow for
installing regular, self-contained sensors? Maybe the target is in a high temperature
or chemically aggressive environment. Perhaps the target is small or very fast-moving.
Fiber-optics, applied to photoelectric scanning, solves these problems.
Fiber Optics and Sensing
All fiber optic sensing mode are implemented using one type of amplifier which contains
both emitter and receiver in one housing.
Fiber Optic Thru-beam Scanning
Using two opposed, individual fiber optic cables, the object to be detected breaks the
beam. The target must be at least the same dimension as the effective beam, which in
this case, is the bundle diameter. Because the beam is very small, the detection can be
very precise. A typical application might be edge detection for a web printing press.
Needle tips reduce the beam dimension for use with extremely small targets, typical for
application in semiconductors and pharmaceutical industries.
Typical application:
• Small parts detection
• Edge detection
• High temperature environment (600 degrees F+)

Fiber Optic:
• Not a scanning technique but rather another way of transmitting light beam.
Advantages:
1. High temperature applications 4. Corrosive areas
2. Where space is limited 5. Noise immunity
3. Size and flexibility of fiber leads 6. Color sensing
Target or
Reflector
Thru
(Poka-Yoke) CONCEPT

Polarized:
• Will work only with comercube
reflector or special polarized
reflective tape.
• Will not false trigger when
sensing shiny object.
Advantages:
1. One-sided sensing
2. Does not false trigger off
highly reflective object
3. Senses clear materials
5. Immune to vibration
Target
Polarized
Special
Reflector
(Poka-Yoke) CONCEPT

(Poka-Yoke) CONCEPT
APPLICATION SCAN TECHNIQUE
Small parts detection Fiber optics or Thru scan with aperatures
Long distance scanning Thru scan
High temperature sensing Fiber optic
Shiny object or film detection Polarized scan
Severe environment (Extreme dust or dirt) Thru scan
Limited mounting space Fiber optic
Explosive environment Thru scan or Retro
Washdown environment Thru, Retro-reflective or Diffuse
Analog position sensing Diffuse or Fiber Optic
Conveyor Monitor
- Jam detection
- Part count
- Part position
Polarized, Diffuse or Retro
Vibratory Feeder Fiber optic
Lid or Cap detection Convergent beam or Fiber Optic
Clear bottle detection Polarized or Fiber Optic
Transparent material Polarized scan
Label detection Diffuse or Fiber Optic
Bin or hopper level Thru when using window Diffuse from above
Mold or die clear to close Thru scan or Fiber Optic (high temp)
Max height monitor (i.e. Fork trucks) Thru scan
Opaque material on semitransparent carrier Thru scan
Motion detection All scan type
APPLICATIONS FOR PHOTOELECTRIC SENSORS

(Poka-Yoke) CONCEPT
ADVANTAGES DISADVANTAGES APPLICATIONS
Magnet Operated - Inexpensive - Magnet required - Security and safety
(reed relay) - Very selective target - Sensitive to welding interlocking
identification fields - Sensing thru metal
Hall Effect - Complete switching - Magnetic target only - Keyboard
function is in a single - Extremely sensitive to
integrated circuit industrial environment
- Operates up to 150khz
- High temperature
(150 degrees C)
- Good resolution
Ultrasonic - Senses all materials - Resolution - Anti-collision on AGV
- Repeatability Doors
- Sensitive to background
and environment changes
- Distance limitation to
60mm
Inductive - Resistant to harsh - Presence detection on all
environments kinds of machines
- Easy to install - Very popular
- Very predictable
Capacitive - Senses all materials - Very sensitive to - Level sensing with liquids
- Detects through walls environment changes and non-metallic parts
Photoelectric - Senses all materials - Subject to contamination - Parts detection
- Material handling
- Packaging
- Very popular
Piezo-electric - Torque (automated or
manual)

(Poka-Yoke) CONCEPT
NEW APPLICATIONS:
• Pressure sensing
• Shape sensing
• Weight sensing
• Presence sensing
• Color sensing (dark vs light)
• Torque sensing (Piezo-electric)
• Position sensing
• Custom / adaptive size parts
• Vacuum sensing
• Flow sensing (e.g. gallon / minute)

(Poka-Yoke) CONCEPT
POKA-YOKE Sensors at a Deming Prize Winner
1. Mechanical 9. Heat Sensor
2. Magnetic 10. Gas Sensor
3. Beam Cut 11. Force Sensor
4. Super Sonic 12. Torque Sensor
5. Image Sensor 13. Meter Relay
6. Counter 14. Vibration Sensor
7. Beam Reflector 15. Automatic Measurement
8. Pressure Sensor

(Poka-Yoke) CONCEPT
THE MOST EFFECTIVE TYPES OF ERROR NOTIFICATION MEANS
Getting the Operator’s Attention:
• Visual Signal (flashing light is best)
• Audio Signal (loud and persistent, e.g. burglar alarm)
• Protective Barrier (to prevent defect or operator injury)
• When used: low defect occurrence rate and when
repairs can be made.
Shutting Down the Operation:
• Upon detecting a “non-conformance” the operation
is simply shut down, i.e. the next part will not be
processed.
• When used: relatively higher occurrence rates and
when repairs are not possible.

(Poka-Yoke) CONCEPT
Problem Type
Error Proofing
Installed
Type of
Sensor Used
Type of
Intervention Used
Missing Components Counter to verify Micro-switch Machine interlock
correct number of
components
Pre-counting the None None
number of components
Fixture at the operation Proximity switch Machine interlock
to detect the presence
of component from the
previous operation
Incorrect Processing Process sequence None (all fixtures None
fixturing specially designed)
Wrong Components Verifying component Light transmission Video or audio alarms
shape, weight, or
dimension switches
EXAMPLES OF POKA-YOKE’S
FOR THE THREE MOST COMMON PROBLEMS

(Poka-Yoke) CONCEPT
What is the best method for sensing fluid levels
for a machine?
What is the best method for sensing magnets for
electric motors?
What are three possible methods for sensing burs
on a cylinder bore?
What is the best method for detecting the presence
of an O-ring?
BEST SENSING IDEAS

Four Categories of Errors - Questions to Ask????
Missing Parts
– Is there a model mix such that some models require a
part while others require nothing at all in that location?
– Is the part assembled as a small part after some main
activity?
– Is the part difficult to see after being assembled?

Missing Parts
Is the part :
Unseen or untouched in
subsequent process steps?
Difficult to see during assembly?
Difficult to assemble?
Difficult to see after assembly?
Difficult to differentiate between pre
and post assembly?
Can anything be done to resolve this
in design of product/process?
Can the part be combined with
another part?
Can the part be eliminated?
What can be done to detect whether
the part has been assembled?
Detection device - torque
counter, photoelectric eye over
container, limit switch at
dispenser,....
Lock out subsequent operation if part
is missing.
Lock out device - limit switch,
conductivity sensor...
Implement operator instructions,
visual aids and training as minimum
requirement
YES
NO
NO
Implement Error Proofing
(process/design change and/or
detect/lock out device)
Verify results
YES

Brainstorm Error Proofing Mechanism
• Make visible/obvious if missing
– Color contrast
– Visible at numerous operations and pack
– Use mirrors
– Position of part as moves down line
– Visual aid/picture posted with part present and highlighted
• Redefine process
– Assemble early in process
– Successive check
– Rearrange multiple write-up to eliminate “sometimes do/sometimes don’t”
• Monitor part supply
– Only supply parts needed for that model (no questions-if there are parts present, use
them)
– Lot control, count parts-must equal # pieces produced
• Sensors
– Photoelectric eyes to detect, lock out until corrected
– Limit switch to detect, lock out until corrected
• Modify design
– Eliminate part
Missing Parts - Thought Starters

Misassembled Parts
– Is the operation difficult for the operator to see
as they perform the job?
– Is there an assembly or positioning operation
that can be completed incorrectly?
Four Categories of Errors-Questions to Ask????

Misassembled Parts
Is the part :
Difficult to see during assembly?
Difficult to assemble?
Difficult to see after assembly?
Difficult to differentiate between pre
and post assembly?
Lacking guides or fixtures for proper
assembly or proper alignment?
(guides, fixtures, automation)
another part?
the part has been misassembled?
Detection device - torque counter,
photoelectric eye, limit switch
is misassembled.
requirement
YES
NO
NO
Verify results
YES

• Visual aids
– Visual aid/picture posted with correct position highlighted
• Workplace organization
– Organize for maximum ease and visibility
• Sensors
• Modify/design fixture
– Unable to assemble incorrectly
• Modify design
– Eliminate part
– Prevent misassembly - e.g. two sizes of studs
– Provide guides or references
Misassembled Parts- Thought Starters

 Incorrect Processing
 Is there an operation that requires a recognition of some
characteristic to determine what to do with the part next?
REJECTS
GOOD

Incorrect Processing
Does the operation require recognition
of some characteristic to determine
what to do with the part?
(e.g. Red light indicates place in reject
pile, visual inspection for pre-defined
defects)
(fixtures, automation)
another part?
the part has been incorrectly
processed?
Detection device - reset button,
is incorrectly processed.
requirement
YES
NO
NO
Verify results
YES

• Visual aids
– Quality alert indicating high potential for error
– Fixture or template outlining pre-defined defects
– Bogey or sample boards for visual inspection
– Reset or acknowledge but at the appropriate next operation
– Automate
• Workplace organization
– Separate and clearly label reject locations/containers
• Sensors
Incorrect Processing- Thought Starters

 Incorrect Parts
 Is there a selection of parts in front of the operator that would
allow for the wrong part to be chosen and assembled?

Incorrect Parts
Is there a selection of parts available
at the workstation?
Are similar parts assembled onto the
product at the same location?
(Consolidation, separate operations)
another part?
the incorrect part has been
assembled?
Detection device - bar code,
Lock out subsequent operation if the
incorrect part is detected
requirement
YES
NO
NO
Verify results
YES

• Make visible/obvious if incorrect part
– Color code - match part to product
– Visible at numerous operations and pack
– Position of part as moves down line
– Visual aid/picture posted with correct part present and highlighted
– Rearrange multiple write-up to separate assembly of like parts
• Monitor part supply
– Only supply parts needed for that model
• Sensors
• Modify/design fixture
– Unable to assemble incorrect part
• Modify design
– Eliminate part
– Prevent assembly of incorrect part
Incorrect Parts- Thought Starters

The Error Proofing Process:
– Utilizes a multi-functional approach
– Is driven by Customer Satisfaction and allows for Quick
response and implementation of solutions
– Is used to “Kill” problems
– Is documented in the ‘Problem Solving Document’ (PSD)
– Supports Continuous Improvement Methodology
– Is the ‘Contain’ step in the 5 Step Problem Solving
Process
People
&
Teamwork
5. Evaluate 1. Identify
2. Analyze
3. Plan
4. Implement
Prevent Select
Contain
Correct
Error-Proofing Process
“Quick Response / Quick Implementation”
Institutionalize
the Solution
and the Ongoing
Control
Institutionalize
Continuous
Improvement
Opportunity
Problem Solving Documentation
First Time
Quality
(F.T.Q.)
at
Operation
Departmental
Containment
Station
Network
Internal
Plant
Audit
Customer
Rejects
(PPM)
Systematic
Problem
Solving
Process
Candidates for Error Proofing
Warranty
Information

1% DEFECT RATE (99% YIELD)
OF ALL STATIONS
RESULTS IN 78%
CONFORMING PRODUCTS
Cell 1
Cell 3
Cell 2
Cell 4
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate
1%
Defect
Rate

PROCESS FALLOUT TABLE
Centered Process
Process capability ratio Parts per million defective
0.50 133,600.00
0.75 24,400.00
1.00 2,700.00
1.10 967.00
1.20 318.00
1.30 96.00
1.40 26.00
1.50 6.80
1.60 1.60
1.70 0.34
1.80 0.06
2.00 0.0018

Implementation Procedure:
• Product Tooling Design Phase
¶ Predict Potential Quality Defects during
Product Tooling Design Stage.
Use DFM to modify Tooling Design to
Prevent Potential Defects from Occurring in
Production based on Potential Defects
Identified.
Build Poka-Yoke Devices into the Process
where Design “Fixes” can not be
Incorporated.
ERROR PROOFING

• Production Phase
¶ Retro-fit Poka-Yoke Devices into Existing
Tooling
 Use Quality History to Target Potential Error
Proofing Application Sites
 Obtain Set-Up Operator Input as to Where to
Apply “Error Proofing” Devices as well as
the Type of Devices to Use.
Implementation Procedure (Continued):
ERROR PROOFING

Some Error Proofing Guidelines:
• Standardize Press Shut Heights
• Utilize Digital Process Parameter Gages
• Apply Locating Devices to Dies, Fixtures, Etc.
• Gages Pre-calibrated prior to Start of Set-Up
• Utilize Common/”Quick Connect Fittings and
Clamping Hardware
• “One Way” Loading
• 100% Component Presence Check
• Verify “Machine Cycle Completed”
• Detected “Error” Stops Process
ERROR PROOFING

CASUAL CONNECTIONS BETWEEN DEFECTS AND HUMAN ERRORS
Causes
of Defects
Omitted Processing
Processing Errors
Errors Setting Up Workpieces
Missing Parts
Wrong Parts
Processing Wrong Workpiece
Misoperation
Adjustment Error
Improper Equipment Setup
Improper Tools and Jigs
Human
Errors
International
Misunderstanding
Forgeful
Misidentification
Amateurs
Willful
Inadvertent
Slowness
Non-Supervision
Surprise
Strongly Connected Connected
SOURCE: NKS/Factory Magazine “Poka-Yoke”

To improve the PROCESS by helping
people prevent ERRORS and increase the
chances of DETECTION, so that FAILURE
MODE occurrences are
ELIMINATED.
WORKSHOP OBJECTIVE

DATE OF WORKSHOP:_________________
SHORT TERM F/U DATE:_______________
LONG TERM F/U DATE:________________
Error Proofing Technique Workshop
SUMMARY OF RESULTS
© 1995 Copyright General Motors. All rights reserved.
SUPPLIER:__________________________________________________________________________________
GM SPONSORING DIVISION:___________________________________________________________________
PROCESS:___________________________________________________________________________________________________________________________________________________
PPAP REQUIREMENTS ADDRESSED (Y/N):____________________________
CREATIVITY TEAM NAME & NUMBER:___________________________________________________________
AFTER WORKSHOP
PARAMETERS BEFORE IMPROVED STATE (CURRENT WEEK) SHORT TERM (0-6 MOS) LONG TERM (6-12 MOS)
WORKSHOP MEASURE % IMPROVEMENT MEASURE % IMPROVEMENT MEASURE % IMPROVEMENT
COST OF
QUALITY FORECAST
_________________
ACTUAL
FIRST TIME
QUALITY
FORECAST
_________________
ACTUAL
PROCESS
CAPABILITY
FORECAST
_________________
ACTUAL
OVERALL QUALITY
MEASURE
FORECAST
_________________
ACTUAL
COMMENTS:
Please indicate the measures used: Examples of Cost of Quality improvements = reduced / eliminated scrap &/or rework, reduction of excess inventory.
(Not all measures need to be used during workshop) First Time Quality = improvement in end of line quality results.
Process Capability = improvement in process capability.
Overall Quality Measure = defects per part or rrppm.
TEAM LEADERS:
PHONE:

WHAT IS NECESSARY TO BE
SUCCESSFUL?
• Management Support
• Team Members who:
• Are team players
• Communicate well
• Not afraid to contribute
• Are empowered
• Have the desire to solve problems
• Can make it happen

KEY AREAS:
• OPERATORS & INSPECTORS FROM STUDY
AREA
• PROCESS AND DESIGN ENGINEER
• QUALITY REPRESENTATIVE
• SKILLED TRADES
• MANAGEMENT REPRESENTATIVE - MIDDLE
TO UPPER LEVELS
• MANUFACTURING REPRESENTATIVE
OPTIONAL AREAS:
• MAINTENANCE REPRESENTATIVE
• OTHER TECHNICAL REPRESENTATIVES:
• INDUSTRIAL ENGINEER
• UNION REPRESENTATIVE
TEAM RECOMMENDATION

 KNOWLEDGE AND EXPERIENCE OF THE PROCESS BEING
STUDIED.
 POSSESSING A TEMPERAMENT TO WORK IN TEAMS AND
CONTRIBUTE TO TEAM GOALS.
 WILLING TO MAKE CHANGE AND THINK BEYOND NORMAL
PRACTICES.
 EMPOWERED TO SPEAK FOR ORGANIZATION AND
KNOWLEDGEABLE TO WHOM TO REACH FOR CRITICAL
DECISIONS OR ANSWERS TO QUESTIONS.
 INNOVATIVE AND CREATIVE THINKING PROCESS.
 ABILITY TO REPRESENT AND CONVEY ATTITUDES OF AREA
/ FUNCTION REPRESENTED.
 AWARE OF INDUSTRY AND COMPANIES COMPETITIVE
SITUATION, AND NEED TO CHANGE.
 UNDERSTAND AND ACCEPT THAT THE WORKSHOP
PROCESS MAY INVOLVE LONG HOURS.
TEAM MEMBERS DESIRED BACKGROUND

SUGGESTED INFORMATION
FOR REVIEW
• PFMEA Data
• Internal Audit Information
• Control Plan
• Process Flow
• Root Cause Analysis Performed to Date
• Process Capability
• Customer Rejections/Warranty Information
• Scrap Rate Information by Cause
• Poka-Yoke Devices
• Other?

of 2
CHECKLIST
STATUS ITEM
CONFERENCE ROOM-KICKOFF MEETING DAY ONE, TIME TBD, LARGE ENOUGH FOR TEAM MEMBERS, STAFF, AND VISITORS.
- TRANSPARENCY PROJECTOR
- VHS TAPE MACHINE
- EASEL WITH MARKERS
CONFERENCE ROOM-WRAP-UP MEETING LAST DAY, TIME TBD, LARGE ENOUGH FOR TEAM MEMBERS, STAFF, AND VISITORS.
- VHS TAPE MACHINE
- EASEL WITH MARKERS
CONFERENCE ROOM-FOR EACH WORKSHOP TEAM FROM DAY ONE TILL LAST DAY LARGE ENOUGH FOR UP TO 15 PEOPLE.
- EASEL WITH MULTI-COLORED MARKERS AND PLENTY OF EASEL PAPER
- VHS TAPE MACHINE
- MASKING TAPE
- LAYOUT OF ROOM CONDUCIVE TO GOOD TEAM INVOLVEMENT (NOISE, FURNITURE CONFIGURATION, TEMPERATURE CONTROL).
- ACCESS TO COPY MACHINES FOR COPIES AND TRANSPARENCIES.
- LOCATION CLOSE TO WORKSITE FOR IMPLEMENTATION WORKSHOP.
- BLANK TRANSPARENCIES AND MARKERS AVAILABLE.
BREAKOUT ROOM(S)-FOR WORKSHOP TEAM TO MEET IN SUBGROUPS AT VARIOUS TIMES.
WORKSHOP TEAM MEMBERS SELECTED.
PARTICIPANT REVIEW OF PROCESS AND PURPOSE/EXPECTATIONS (GM TO ASSIST?).
WORKSITE AND AFFECTED AREA REVIEW OF WORKSHOP PLANS AND PURPOSE/EXPECTATIONS (GM TO ASSIST?).
MESSAGE CENTER ARRANGEMENT ESTABLISHED FOR PARTICIPANTS AND VISITORS,
NAME TAGS FOR EACH TEAM MEMBER (NOT STICK ON TYPE).
REFRESHMENTS FOR MORNING AND AFTERNOON (COFFEE, POP, FRUIT, WATER) FOR TEAMS AND KICKOFF MEETING.
LUNCH ARRANGEMENTS TO MINIMIZE TRAVEL TIME (IF PRESET MENU, KEEP ON LIGHT SIDE).
PARTICIPANT MATERIALS AVAILABLE.
- WRITING PAD & PEN
- SAFETY EQUIPMENT
- WORKSHEETS (GM TO PROVIDE)
- CLIPBOARD OR HARD WRITING SURFACE
OTHER ATTENDEES FOR KICKOFF AND WRAP-UP MEETING IDENTIFIED.

of 2
CHECKLIST
STATUS ITEM
WORKSHOP WORKSITE INFORMATION PROVIDED/AVAILABLE:
- PLANT LAYOUT OF WORKSITE AREA SHOWING PRODUCT FLOW AND OPERATORS (ON 8 1/2 X 11 PAPER).
- CUSTOMER SPECIFICATIONS AND REQUIREMENTS.
- EQUIPMENT PROCESS CAPABILITY AND PERFORMANCE RECORDS AVAILABLE.
- INTERNAL PLANT AUDIT INFORMATION.
- CUSTOMER REJECTIONS BY TYPE AND CAUSE
- REJECTION RATE (IN-PROCESS SCRAP)
- SETUP REQUIREMENTS (PEOPLE & TIME)
- CHANGEOVER TIME
- EQUIPMENT DOWNTIME OR UPTIME
- PFMEA DATA
- PROCESS FLOW INFORMATION AND CONTROL PLAN DATA
DRESS CODE ESTABLISHED AS CASUAL PLUS PLANT SAFETY REQUIREMENTS (E.G. HARD SOLE SHOES, LONG SLEEVES, ETC).
TRANSPARENCY DESCRIBING ADMINISTRATIVE DETAILS:
- LAYOUT AND LOCATION OF CONFERENCE ROOMS.
- REST ROOM LOCATIONS.
- LUNCH ARRANGEMENTS
- LIST OF ATTENDEES/PARTICIPANTS BY NAME, COMPANY, AND TITLE
- SAFETY REQUIREMENTS
- MESSAGE CENTER(S)
- PHONE LOCATIONS
- SMOKING REGULATIONS (NO SMOKING IN CONFERENCE AND TEAM ROOMS REQUESTED)
FINALIZE OPENING KICKOFF SPEAKER IDENTIFICATION, TIMING, AND CONTENT.
MTG ARRANGED FOR END OF EACH DAY WITH TOP MANAGEMENT AND TEAM LEADERS TO REVIEW STATUS/ADDRESS ROADBLOCKS.
LOGISTIC ARRANGEMENTS MADE TO ALLOW GM PERSONNEL TO DRIVE DAILY ON PLANT PROPERTY TO WORKSITE/MEETING ROOMS.

NAME COMPANY CURRENT JOB ASSIGNMENT BUSINESS PHONE
ATTENDEES

DATE OF WORKSHOP:_________________
SHORT TERM F/U DATE:_______________
LONG TERM F/U DATE:________________
Error Proofing Technique Workshop
SUMMARY OF RESULTS
SUPPLIER:__________________________________________________________________________________
GM SPONSORING DIVISION:___________________________________________________________________
PROCESS:___________________________________________________________________________________________________________________________________________________
CREATIVITY TEAM NAME & NUMBER:___________________________________________________________
PARAMETERS
COST OF
QUALITY
_________________
FIRST TIME
QUALITY
_________________
PROCESS
CAPABILITY
_________________
OVERALL QUALITY
MEASURE
_________________
COMMENTS:
Please indicate the measures used:
TEAM LEADERS:
PHONE:

DEFINE CURRENT STATE
• AREAS OF INVESTIGATION AND CONFIRMATION:
• PROCESS FLOW DIAGRAM
• REVIEW OF PROBLEM AREA
• PFMEA
• INTERNAL AUDITS AND INFORMATION
• ROOT CAUSE ANALYSIS EFFORTS TO DATE
• CUSTOMER REJECTIONS
• CONTROL PLANS
• COMPLETE “SUMMARY OF RESULTS” CURRENT STATE

POTENTIAL
(PROCESS FMEA) FMEA Number ________________________________
Page _________ of ___________________________
Item________________________ Process Responsibility______________________ Prepared by __________________________________
Model Year(s) / Vehicle(s)_______________________Key Date________________________________ FMEA Date (Orig.)________________ (Rev.)________
Core Team______________________________________________________________________________________________________________________________________________________________
9 10 11 12 13 14 15 16 17 18 19 20 21 22
Process C O D Action Results
Function l Potential c e
Potential Potential S a Cause(s)/ c Current t R. Responsibility S O D R.
Failure Effect(s) E s Mechanism(s) u Process e P. Recommended & Target Actions e c e P.
Requirements Mode of Failure V s of Failure r Controls c N. Actions Completion Date Taken v c t N.
EPFORM-L.PPT Pg.1
02/13/00
FAILURE MODE AND EFFECTS ANALYSIS

Potential Error EP # Error Proofing Mechanism Level of Install Operator Process Audit
Control Date Instruct. # Method Frequency Responsible
ERROR PROOFING CONTROL PLAN

DATE: __________
SHORT TERM F/U DATE:________
LONG TERM F/U DATE:_________
Error Proofing Techniques SUMMARY OF RESULTS
SUPPLIER:__________________________________________________________________________________
GM SPONSORING DIVISION:_____________________________________________________________
PROCESS:__________________________________________________________________________________________________________________________________
CREATIVITY TEAM NAME & NUMBER:______________________________________________________
PARAMETERS
COST OF
QUALITY
_________________
FIRST TIME
QUALITY
_________________
PROCESS
CAPABILITY
_________________
OVERALL QUALITY
MEASURE
_________________
COMMENTS:
Please indicate the measures used:
TEAM LEADERS:
PHONE:

WHAT IS
ERROR
PROOFING?
HOW AND
WHERE DO WE
APPLY IT?

PURPOSE OF ERROR PROOFING EFFORT:
• Drive simple and inexpensive devices into our processes
to help people notice errors
KEY CONCEPTS / ASSUMPTIONS:
• People want to do a good job
• People make mistakes
• An error only becomes a defect if it’s passed on
• The only way to notice errors is to have devices do
100% inspection (not people)
WHY DO WE SUGGEST ERROR PROOFING?

SOURCES OF DEFECTS
 OMITTED PROCESSING
 PROCESSING ERRORS
 ERRORS SETTING UP WORKPIECES
 MISSING PARTS
 WRONG PARTS
 PROCESSING WRONG WORKPIECE
 MISOPERATION
 ADJUSTMENT ERROR
 EQUIPMENT NOT SET UP PROPERLY
 TOOLS AND JIGS IMPROPERLY PREPARED

DIFFERENT KINDS OF ERRORS
 FORGETFULNESS
 ERRORS DUE TO MISUNDERSTANDING
 ERRORS IN IDENTIFICATION
 ERRORS MADE BY AMATEURS
 WILLFUL ERRORS
 INADVERTENT ERRORS
 ERRORS DUE TO SLOWNESS
 ERRORS DUE TO THE LACK OF STANDARDS
 SURPRISE ERRORS
 INTENTIONAL ERRORS

FIVE TYPES OF
DEFECT OCCURRENCES
1. INAPPROPRIATE STANDARD OPERATING
PROCEDURES OR METHODS.
2. TOO MUCH VARIABILITY IN ACTUAL
OPERATIONS EVEN THOUGH STANDARD
METHODS ARE APPROPRIATE.
(CARRY OUT PROPER MAINTENANCE BEFORE OPERATIONS
BEGIN)
3. DAMAGED MATERIALS OR EXCESSIVE
VARIABILITY IN THICKNESS.
(USE APPROPRIATE MATERIALS AND INSPECT CAREFULLY ON
RECEIPT)

4. WORN MACHINE BEARINGS
OR TOOLS
(CARRY OUT THOROUGH MAINTENANCE AND
TOOL MANAGEMENT)
5. SIMPLE MISTAKES OR
IMPERFECTLY
CONTROLLED TASK
EXECUTION
FIVE TYPES OF DEFECT OCCURRENCES

ZERO QUALITY CONTROL
COMPONENTS
• SOURCE INSPECTION:
• Checks for factors that cause errors, not the resulting defect.
(Locator pin)
• 100% INSPECTION:
• Uses inexpensive Poka-Yoke devices to inspect automatically
for errors or defective operating conditions. (Limit switch).
• IMMEDIATE CORRECTIVE ACTION:
• Operations are stopped instantly when a mistake is made and
not resumed until it’s corrected. (Machine is shut down)
• RECOGNIZE THAT PEOPLE ARE HUMAN AND USE
POKA-YOKE DEVICES TO FULFILL “CHECKING
FUNCTIONS”.

SOURCE INSPECTION
MANAGEMENT CYCLE
CAUSE
RESULT
Error
Action
Check
and
feedback
Defect
Action
Check
and
feedback
(small cycle)
Conventional Defect
Management Cycle
(large cycle)
1. Shingo wants to set-up
many of these small
circles.
4. These are multiple
assembly operations.
3. Shingo wants to
discourage these
or make shorter.
5. This is an end of line
inspection station.
2. View these as one
operator’s station.

Techniques:
• Design For Manufacturability
(DFM)
Technique that Results in Designs that Cannot
be Incorrectly Manufactured or Assembled.
This Technique can also be used to “Simplify”
the Design and therefore reduce it’s cost.
ERROR PROOFING

DESIGN STAGE - BEST OPPORTUNITY TO
IMPACT QUALITY & COST
TIME
CHANCES FOR
QUALITY & COST
IMPROVEMENTS
COST TO
IMPLEMENT
COST
START OF PRODUCTION

DESIGN PREVENTS MISASSEMBLY

Techniques (Continued)
• “Poka-Yoke” System*
Set-Up Devices or Inspection Techniques that
Assure that Set-Up is Done Correctly; i.e.
Produces 100% Good Parts from the First Piece
on
“Zero Quality Control: Source Inspection and the Poka-Yoke System” - Shigeo
Shingo; 1986
ERROR PROOFING

ERROR PROOFING THE PROCESS
Problem: Missing Weld Nuts
• Automatically
Stops Process
• Provides Visual
& Audio Control
Up
Down
Height of Nut
Up
Down
Welding Machine
Nut
Product

Effective Error Proofing
techniques can reduce or
eliminate our dependence
on operator knowledge and
vigilance, therefore
reducing the number of
defects we send to our
customers!!

Levels of Error Proofing
No
Controls
Instructio
n
Training /
Visual Aids
Visual
Control
s
Containment*
- 100% Inspect
Defect Detection
- Stops Process
Avoidance
- Robust Product /
Process Designs
- Autonomation
AWARENESS DETECTION PREVENTION
* 100% inspection for containment of a defect should be implemented only as a temporary fix, as it, too, is subject
to operator vigilance.

BASIC FUNCTIONS OF A
POKA-YOKE SYSTEM
• SHUTDOWN
• CONTROL
• WARNING

DETECTION DEVICES FOR
POKA-YOKE SYSTEMS
 CONTACT DETECTION DEVICES
 NON-CONTACT DETECTION DEVICES
 DEVICES THAT DETECT PRESSURE,
TEMPERATURE, ELECTRIC CURRENT,
VIBRATION, CYCLES, TIME, TIMING AND
INFORMATION TRANSMISSION

CONTACT DETECTION DEVICES
 LIMIT SWITCHES
 MICRO SWITCHES
 TOUCH SWITCHES
 DIFFERENTIAL
TRANSFORMERS
 TRIMETRONS
 LIQUID LEVEL RELAYS

NON CONTACT DETECTION DEVICES
 PROXIMITY SWITCHES
 PHOTOELECTRIC SWITCHES
 BEAM SENSORS
 FIBER SENSORS
 AREA SENSORS
 DIMENSION SENSORS
 DISPLACEMENT SENSORS
 METAL PASSAGE SENSORS
 COLOR MARKING SENSORS
 DOUBLE-FEED SENSORS
 WELDING POSITION SENSORS
 TAP SENSORS
 FLUID SENSORS

FIVE BEST POKA-YOKE
1. GUIDE PINS OF DIFFERENT SIZES
2. ERROR DETECTION AND ALARMS
3. LIMIT SWITCHES
4. COUNTERS
5. CHECKLIST(S)

Where Poka-Yoke
is technically
or economically
unfeasible in
self-check system...
Incorporate
Poka-Yoke
functions
into successive
check systems.

• Missing Parts
– Forgetting to assemble a part - screws, labels, orifice tubes...
• Misassembled Parts
– Misassembly - loose parts, upside down, not aligned
• Incorrect Processing
– Disposing of a part rejected at test to the wrong pile
• Incorrect Parts
– Retrieving and assembling the wrong part from a model mix selection -

PROBLEM SOLVING PROCESS
For Customer Satisfaction
Institutionalize
Continuous
Improvement
Opportunity
People
&
Teamwork
5. Evaluate 1. Identify
2. Analyze
3. Plan
4. Implement
Prevent Select
Contain
Correct

TEAM PROCESS
STEP:
1. IDENTIFY FAILURES
PRIORITIZE FAILURES
SELECT ONE
DOCUMENT CURRENT CONDITION
2. ROOT CAUSE ANALYSIS
WHY - WHY
FLOOR REVIEW
INVESTIGATION
3. BRAINSTORM ERROR PROOF DEVICES
SELECT BEST IDEAS
PLAN IMPLEMENTATION
4. IMPLEMENT IDEAS
COMPLETE BEFORE AND AFTER DOCUMENT
5. COMPLETE FUTURE ACTION PLANS
DOCUMENT NEW CONDITION
SELECT NEXT FAILURE AND BEGIN STEP 1

IMPLEMENTATION
• TRY DIFFERENT IDEAS
• Error Proofing Device / Tool
• New Containers
• Different Process (ask Employees to try)
• Different Flow of Materials
• Detection of Defects
• Re-route
• CALL SOMEONE
• Packaging
• Design Changes
• Layout Changes
• Approvals from Division
• PAPERWORK
• Write P.M. Process
• Re-Write Process Steps
• Purchase Order
• Revise / Revised Layout

• Criticism Forbidden
• Freewheeling Encouraged
• Quantity (Going for a lot of ideas)
• Combine and Expand - Hitch-hiking
OSBORN’S RULES FOR
BRAINSTORMING

Error Proofing.ppt

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