PPT in support of two-day workshop on "Error-Proofing" (Poka Yoke) of industrial work processes

1. ERROR PROOFING
Quest

2. 1/19/99 © Johnson Controls, Inc. errorprf.ppt2
Objectives:
By the end of this Workshop, be
able to….
• Identify 3 approaches to inspection….
• Identify specific conditions that provoke errors (Red
Flags)….
• Use Source Inspection to prevent defects….
• Name error-proofing devices and applications….
• Implement Error-Proofing in your workplace….

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Logistics
• Start/End Times
• Participation
• Lunch Area/Timing
• Meeting Location(s)
• Restroom(s)
• Telephones, Messages, Pages
• Call in Number
• Refreshments
• Timekeeper

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3 Basic Principles
• Error Proofing is Achievable
Zero Tolerance For Waste
• Stable Production Environment
(eliminate Operator/machine possible error)
• Customer “Pull” Drives Production

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What will Quality be in the 21st
Century?
 Continue to be defined by customers
 Will be less of a competitive advantage
 Will be ‘taken for granted’ (expected)
 Will require routine use of Quality tools
 Will require more creativity

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Error Proofing Means
“Zero Tolerance for Waste”
• Fundamental belief that all errors, and
the defects they cause, can be prevented
= zero waste!
• Waste of correction/rework is reduced
(You MUST believe th is for Poke Yoke to
work)

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EVIDENCES
 AT&T Power Systems reduced outgoing defects
by 70% (Won Deming Prize)
 TRW reduced customer PPM’s from 288 to 2
 Washing machine drain pipe assembly line
produced 180,000 units, in 6 months, with 0
defects.
 Your experiences?
Source: Productivity, Inc.

8. Error Proofing Means
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“Stable Production
Environment”
• An error-proofed process is repeatable..
• An error-proofed process is predictable
• An error-proofed process is stable.
• An error-proofed process produces
higher quality product.
 Repeatable
 Predictable
 Stable
 Leads to Higher Quality

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Error Proofing Supports
“Customer Pull’
• An error-proofed process “gets it right the first
time” more often.
• Improved flexibility to respond to customer
demands.
• Improved quality reduces the wastes
associated with “inspecting quality into the
product.”
• Inspection done @ source

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Error Proofing Opportunities

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Error Proofing (Poka-Yoke)
• Improves product quality and ensures
consistent process results.
• Emphasizes designing the manufacturing
process to ensure zero defects.
• Requires disciplined problem-solving and
beliefs that defects are not inevitable in
production shops.
• Is effective when done in teams.

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• Name some products, services where you
are used to receiving high quality every
time....
• Any bad product or service experiences?
• Are high quality products achievable every
time?

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How Can We Ensure Quality
in the Following Areas?
Man
Material
Machine
Method
Information
(4M + I)

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5 Elements of Production
4. Method
Control: Assembly Line
& Work Standards
3. Machine
Control: Conditions Assured
Through Poka-Yoke &
Everyone's Participation
5. Information
Control: Visual Controls
(Instruction Sheets,
Kanban)
1. Me
Control: Discipline,
Fundamental Education,
Cross-Training Assignments
2. Material
Control: Source Controls

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Inspection Techniques
 Judgement (inspection)
 Informative (inspection)
 Source (inspection)
Remember Shaving?

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Judgment Inspection
“Then
and
There”

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Informative Inspection
• Feedback provided to upstream processes
when defects are discovered.
• Uses statistics and sampling.
• Seeks to minimize defects.

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Informative Inspection

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Source Inspection
• Operations examined for conditions that may
breed defects.
• Emphasis on data collection and problem
solving.
• 100% inspection built into each operation.

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Self-Checking for Errors
(Builds out Operator Error)
• Work verified before it leaves station
• Build sensory + visual aids into operation
• Represents 100% source inspection
• Workers responsible to implement quality
control
• Standards must be followed for success

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Self-Checking for Errors

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Successive Checking for Errors
• Users of upstream work verify part or process
for correctness before use
• Prevents cumulative errors
• Builds teamwork between operations.

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Successive Checking for Errors

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Defects vs. Errors
• Analyzing the production process to achieve zero
defects = Distinguishing between defects and
errors
• Defects = results (effects of mistakes )
• Errors = sources (causes of mistakes)

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Error Defect
Not tightening lug-nuts Loose metal
Setting too dark on toaster Burnt toast
Failing to clean metal Dirt in paint

26. Some Common
Manufacturing Errors
Quest

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Most Common
Manufacturing Errors
• Omitted processing
• Processing errors
• Workpiece setup
• Missing parts
• Wrong parts
• Processing wrong workpieces
• Misoperation
• Adjustment errors
• Improper equipment set-up
• Tools & jigs improperly prepared

28. Why Do People
Make Mistakes?
Quest

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Most Common Human Errors
• Forgetfulness - Lack of task priorities
• Misunderstanding - Lack of familiarity with
process
• Identification - Misreading visual cues
• Poor training - Lack of experience,
reinforcement
• Intentional - Deliberate mistake
• Willful - Ignoring rules without harmful
intent
• Inadvertent - Unaware of mistake
• Slowness - Delays in judgement or physical
ability
• Poor Supervision - Unclear, contradictory
instructions
• Surprise - Errors due to abnormal events

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Manufacturing & Human Errors
• Common human errors can be
eliminated through process design
• Defects are not inevitable
• You can achieve Zero Defects!

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Red Flags
(When These Things Happen…)
* Adjustments
* Tooling/tooling change
* Dimensionality/specification/critical condition
* Many parts/mixed parts
* Multiple steps
* Infrequent production
* Lack of or ineffective standards
* Symmetry
* Asymmetry
* Rapid repetition
* High volume/extreme high volume
* Environmental conditions

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Adjustments
reference pin divergence
Having to bring parts,
tools or fixtures into
a correct relative
position only by
sight or feel.
correct incorrect

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Tooling/Tooling Change
Defects From Malfunctions or Incorrect
Tooling
holder
glue
laminated
surface
Spots

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Dimensionality/Specification/
Critical Condition
Relying solely on
Operator skill for
proper job setup
or precision work

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Many Parts/Mixed Parts
Operations without
safeguards to
prevent use of
incorrect parts

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Multiple Steps
Work requiring
many small
operations or sub-
tasks

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Infrequent Production
Intermittent
operations, or
production

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Symmetry
Model X
Condition that
allows parts to be
installed upside
down or in
mirror image
position

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Asymmetry
pointer boss
pointer
washer
Where opposite sides
of a part, tool or fixture
look identical but can
only be used correctly
one way.
bottom die has a flat surface

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Rapid Repetition
From Automatic
Welding Machine Repeating the same work over
and over so that errors are
not readily detected
Shaft Omitted
Next Process

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High Volume
right side up upside down
Operations
where output
is large & fast
so that errors
workpiece
escape visual
inspection

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Environment
Physical conditions around the workplace that can
adversely impact quality
wire stock to machine
dimensional
variation foreign
matter
tension
device
reel stand

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Red Flag Conditions S S
s
ion
io n tio
n dit
s on di t c on
rn du on e al
C
ts ce c C ps ro it i nt
en Con Spe arts e Ste ent P SOP ry ry epit lum me
tm g l P l u f et et R o n
jus lin tica ed ltip eq k o m mm id h V viro
Operation Ad Too Cri Mix Mu Infr Lac Sym Asy Rap Hig En Comments

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Quality Data Review
• Review top 3 quality issues (in dollars or
PPM) in our area for the previous month.
• Review top 3 quality issues (dollars or PPM)
in our area for the previous 3 months.
• Determine which errors reoccur.

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Production Shop Exercise
(60 min.)
• Form teams.
• Decide on line/area to review.
• Review operation(s) to Red Flag, using standard
form.
• Consolidate ideas into groups.
• Present for discussion.

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Team Debrief
• Describe Red Flag Conditions Found in Your
Area.
• How Do These Conditions Affect Quality?

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Implementation of Error-
Proofing
• Identify product defect & collect data
• Track defect at:
– Point Discovered
– Point Created
• Review SOP at defect creation point
• Identify any deviations from SOP
• Identify Red Flag condition at creation point
• Implement error-proofing device to prevent error or
defect
• Check results & make process adjustments

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Describe Product Defect & Collect
Data
Problem: Missing Nut Bracket Screws
Defects
25
20
15
10
5
0
1 2 3 4 5 6 7 8
Hour
Are You Capturing This Information?

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Identify Two Key Locations
Defect creation &
discovery points

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Review SOP at
Creation Point
Is there an SOP? Deviations?
I've been using I've been using slot
Phillips head head screws!
screws!
Service
Manual

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Error-Proofing Devices
• Level 1 (Prevention: Ideal!)
Eliminate error at the source
• Level 2 (Detection)
Detects errors in the process of occurring, before it has
become a defect
• Level 3 (Detection)
Detects a defect after it has been made but before it
leaves the station

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Prevent Defects by:
• Shutdown (Level 1)
- Processing stopped until error is
corrected.
• Controls (Level 1)
- Only allowing parts to fit into jigs,
fixtures in the correct position.

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Error & Defect Detection
• Error Detection (Level 2)
– Detects errors as they are being
made.
• Defect Detection (Level 3)
– Detects defects before they leave station.

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Common Detection
Function & Devices
Detection Functions Device
Pressure gauges, pressure-sensitive switches
Temperature thermometers, thermostats,
thermistors, thermocouples
Electric Current meter relays, current eyes
Vibration vibration sensors
Cycles counters, stepping relays, fiber
sensors
Time times, delay relays, timing units,
time switches
Information buzzers, lamps, flashing lamps

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Error-Proofing Devices:
Visual Devices

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Jigs
Desired Drilled Holes
Groove
Jig
Limit Switch
Groove
L/S Workpiece Correct
L/S Workpiece Incorrect

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Photoelectric Devices & Optics

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Contact Devices

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Counters
000004

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Checklists
Packing Checksheet
Hubcap Covers (4)
Owner's Manual (1)
Radio Manual (1)
Floor Mats (4)
Tire Manual (1)
Plant Decal (1)

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Shop Floor Application
• Describe defect (error). (Write it down, draw
it, etc.)
• Plot defect rate. (Pareto charts, histograms)
• Identify where defect is discovered and made
• Detail SOP (What is SOP here?)
• Identify deviations from SOP
• Identify causes for deviations (Fishbone?
Brainstorming?)
• Identify Red Flag conditions
• Identify source errors
• Propose ideas to eliminate or detect errors
• Propose possible error-proofing devices

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Summary
• Zero defects are possible if you build
100% inspection checks into every
process.
• The production process can be designed
to prevent & detect human errors.
• Team skills facilitate error-proofing.

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Summary
• Source inspection & successive
checking are the foundations of error-
proofing.
• Error-proofing should be considered
where an operation contains Red
Flags.
• Error-proofing devices need not be
expensive or high-tech.

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HAVE FUN!