Poka yoke error proofing

Poka Yoke (Mistake Proofing)
Making it impossible for errors to be passed to the next step in a process

Poka Yoke - Content
What is it for?
• To eliminate the possibility or opportunity for passing on errors or
making mistakes in a process.
Where could I use it?
How do I use it?
• In the development or improvement of any process.
• When you want to make wrong actions impossible or more difficult to do.
• When there is a need to make it possible to reverse actions – to “undo”
them – or make it harder to do what cannot be reversed
• When you need to make it easier to discover that errors occur.
Risks and how to avoid them
• Identify the errors/mistakes which could be passed on
• Develop potential solutions to prevent errors
• Develop potential solutions to detect errors
• Implement solutions
Example

Expected Benefits:
• Poka Yoke ensures that mistakes are not transferred to the next step of the process.
• Poka Yoke solutions are a simple and low costway to reduce rework
Uses of this tool:
• Used to develop solutions to prevent mistakes before theyoccur or to detecterrors and make it
impossible forthem to be passed on to the next step of the process.
• Can be used in the developmentof a new process orin an existing process where rework to correct
errors is hurting process effectivenessand efficiency.
Poka Yoke - What is it for?

Background:
• Mistakes are human errors that result from
incorrectintentions or executing correct
intentions that result in unintended outcomes.
• The term poka-yoke comes from the
Japanese words poka (accidental mistake)
and yoke (prevent).Also known as ‘mistake-
proofing’ or “error-proofing”.
• Shigeo Shingo developedpoka-yoke while
working at Toyota in the 1960’s
Uses:
• Use it to eliminates the cause of an error at the
source or as it is being made.
• Use it to detectan error soon after it has been
made, but before itreaches the next operation.
• In the developmentor improvementof any
process.
• When you want to make wrong actions more
difficult.
• When there is a need to make it possibleto
reverse actions – to “undo” them – or make it
harder to do what cannot be reversed
• When you need to make it easier to discoverthat
errors occur.
• When you want to reverse incorrect actions
Poka Yoke - Where could I use it?

Poka Yoke - How do I use it?
Define the potential
mistakes /errors
Procedure and Guidance Notes:
• List potential mistakes / errors which could be transferred to the next
step in the process.
Combine this with other tools (such as
brainstorming).
Develop ways to
prevent errors
• Investigate and analyse root causes Use other techniques such as Fishbone and
5 Whys for this step
Develop ways to
detect errors
• Brainstorm potential solutions for preventing the error
Make it obvious when something has been
done incorrectly. E.g. make a system to identify
product defects by testing the product's shape,
size, color, or other physical attributes
Create & test
solution
• Brainstorm ideas to detect the error / deviation or mistake early
Consider characteristics of Poka Yoke
solutions:
Simple and low cost
Part of the process
In place where the mistake can occur
Does not let the mistake exit the process
Identify
Root Causes
Implement solution
Find ways to make it impossible to do
something incorrectly
• Develop solution to prevent or detect errors and test that it is effective.
• Implement solution and control output is effective (i.e. Errors are
prevented and/or detected)

Poka Yoke - Risks and how to avoid them:
Risks :
• Not all potential errors are eliminated or detected
• Solutions are duplicated at different stages of the
process.
• Potential solutions are complex and expensive
Steps to avoid them :
• Make a thorough list of potential problems – use other
techniques, such as brainstorming to help and use the
team. Use as many Poka Yoke devices as is
necessary.
• Use flow charts to visualize the process so that
mistake proofing solutions are not repeated
• Consider simple and cost effective solutions.

QUALITY STEPCHART
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 CONTROLLEDSHIPPING
• 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.
• ESTABLISHIMPLEMENTATIONTIMING AND
RESPONSIBILITY.
PLAN & IMPLEMENT
CORRECTIVE ACTION
• BASED ON PROFOUNDKNOWLEDGE
• 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
O PER
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03/ 23/ 94
1
2
3
4
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MAKE ALL PEOPLE
AFFECTED AWARE
OF WHAT IS
GOING TO HAPPEN
DEFINE
CURRENT
SITUATION

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 - ProblemSolving SolutionsUtilizing
DEVELOPACTION PLANS & IMPLEMENTATION
CLOSING & WRAP-UP

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

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 landingsat O’HareAirport each day
• 16,000 lost pieces of mail per hour
• 20,000 incorrectdrug 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!!!!

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.

Awareness: Having the forethoughtthat a mistake can be made, communicating the potential, and
planning the designof the productor processto detector prevent it.
Detection: Allowing the mistake to happen but providing some means of detecting it and alerting
someone sothat we fix it before sending it to our customer.
Prevention: Not allowing the possibilityfor the mistake to occurin 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 Devicesor Inspection Techniquesthat Assurethat
Set-Up is DoneCorrectly;i.e. Produces 100%Good Parts
from the First Pieceon
“Zero Quality Control: Source Inspection and the Poka-Yoke System” - Shigeo Shingo; 1986
ERROR PROOFING

MissingParts
✓ 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...
EXAMPLES OF ERRORS AT WORK . . .

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)
ERROR PROOFING TECHNIQUES
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
Typicalrange: 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.
Bestapplications for magnetically actuatedswitches 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 (movingparts)

(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 respondrapidly to
parts moving quickly and in varying positions along a conveyor,yet operate
dependablyif actuated only infrequently. There are controls forindoor or
outdooruse, 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 LevelControl
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 suppressionutilizes 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 outputof both receivesare equal.
Applications:
• Material handling - conveying systems
• Collision detectionforAGV’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
ConvergentBeam
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.
Typicalapplication:
• 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 THREEMOST 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

BrainstormError ProofingMechanism
• 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

Brainstorm Error Proofing Mechanism
• 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 SolvingDocumentation
First Time
Quality
(F.T.Q.)
at
Operation
Departmental
Containment
Station
Network
Internal
Plant
Audit
Customer
Rejects
(PPM)
Systematic
Problem
Solving
Process
Candidatesfor 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 WrongWorkpiece
Misoperation
AdjustmentError
Improper EquipmentSetup
Improper Tools andJigs
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

S u p p lie r: L o c a tio n :
G M B u y e r: C re a tivity Te a m :
A c tivity Ty p e : S D E :
A c tivity D a te : F o llo w u p D a te s : -
N o . A ctio n Ite m R e sp o nsib ility Ta rg e t P rogres s
D a te C om m ents
W o rksh o p Actio n Item s

DATE OF WORKSHOP:_________________
SHORT TERM F/U DATE:_______________
LONG TERM F/U DATE:________________
Error Proofing Technique Workshop
SUMMARY OF RESULTS
© 1995 CopyrightGeneral 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 ATEMPERAMENT TO WORK INTEAMS AND
CONTRIBUTETO TEAMGOALS.
• WILLING TO MAKE CHANGE AND THINK BEYOND NORMAL
PRACTICES.
• EMPOWERED TO SPEAK FOR ORGANIZATIONAND
KNOWLEDGEABLETO WHOM TO REACH FOR CRITICAL
DECISIONS OR ANSWERS TO QUESTIONS.
• INNOVATIVE AND CREATIVETHINKING PROCESS.
• ABILITYTO REPRESENT AND CONVEYATTITUDES OF AREA
/ FUNCTION REPRESENTED.
• AWARE OF INDUSTRYAND COMPANIES COMPETITIVE
SITUATION,AND NEED TO CHANGE.
• UNDERSTAND AND ACCEPTTHATTHE WORKSHOP
PROCESS MAYINVOLVELONG 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

N o . A ctio n Ite m R e sp o nsib ility Ta rg e t P rogres s
D a te C om m ents
W o rksh o p A ctio n Item s

DATE OF WORKSHOP:_________________
SHORT TERM F/U DATE:_______________
LONG TERM F/U DATE:________________
Error Proofing TechniqueWorkshop
SUMMARY OF RESULTS
SUPPLIER:__________________________________________________________________________________
GM SPONSORING DIVISION:___________________________________________________________________
PROCESS:__________________________________________________________________________________________________________________________________________________
CREATIVITY TEAM NAME & NUMBER:___________________________________________________________
AFTER WORKSHOP
COST OF
QUALITY FORECAST
_________________
ACTUAL
FIRST TIME
QUALITY
FORECAST
_________________
ACTUAL
PROCESS
CAPABILITY
FORECAST
_________________
ACTUAL
OVERALL QUALITY
MEASURE
FORECAST
_________________
ACTUAL
COMMENTS:
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

N o . A c tio n Ite m R e s p o ns ib ility Ta rg e t P rogres s
D a te C om m ents
W o rksh o p A ctio n Item s

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:_____________________________________________________
AFTER WORKSHOP
COST OF
QUALITY
FORECAST
_________________
ACTUAL
FIRST TIME
QUALITY
FORECAST
_________________
ACTUAL
PROCESS
CAPABILITY
FORECAST
_________________
ACTUAL
OVERALL QUALITY
MEASURE
FORECAST
_________________
ACTUAL
COMMENTS:
TEAM LEADERS:
PHONE:

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

PURPOSE OF ERROR PROOFING EFFORT:
• Drive simple and inexpensivedevices into our processes
to help people notice errors
KEY CONCEPTS / ASSUMPTIONS:
• Peoplewant to do a good job
• Peoplemake mistakes
• An erroronly becomes a defect if it’s passedon
• 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
(CARRYOUT THOROUGHMAINTENANCEAND
TOOLMANAGEMENT)
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 CORRECTIVEACTION:
• Operations are stopped instantly when a mistake is made and
not resumed until it’s corrected. (Machine is shut down)
• RECOGNIZE THAT PEOPLEARE 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

EffectiveError Proofing
techniques can reduce or
eliminateour dependence
on operatorknowledgeand
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
• PHOTOELECTRICSWITCHES
• BEAM SENSORS
• FIBER SENSORS
• AREA SENSORS
• DIMENSION SENSORS
• DISPLACEMENTSENSORS
• METAL PASSAGE SENSORS
• COLOR MARKING SENSORS
• DOUBLE-FEEDSENSORS
• WELDINGPOSITION 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
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...
EXAMPLES OF ERRORS AT WORK . . .

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. IDENTIFYFAILURES
PRIORITIZE FAILURES
SELECTONE
DOCUMENT CURRENT CONDITION
2. ROOT CAUSE ANALYSIS
WHY - WHY
FLOOR REVIEW
INVESTIGATION
3. BRAINSTORMERROR PROOFDEVICES
SELECTBEST IDEAS
PLAN IMPLEMENTATION
4. IMPLEMENT IDEAS
COMPLETE BEFORE AND AFTER DOCUMENT
5. COMPLETE FUTURE ACTIONPLANS
DOCUMENT NEW CONDITION
SELECT NEXT FAILURE ANDBEGIN STEP1

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

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