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National GuardBlack Belt Training
National GuardBlack Belt Training
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Module 46
Mistake Proofing (Poka Yoke)
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CPI Roadmap – Improve
Note: Activities and tools vary by project. Lists provided here are not necessarily all-inclusive.
TOOLS
•Brainstorming
•Replenishment Pull/Kanban
•Stocking Strategy
•Process Flow Improvement
•Process Balancing
•Standard Work
•Quick Change Over
•Design of Experiments (DOE)
•Solution Selection Matrix
• ‘To-Be’ Process Mapping
•Poka-Yoke
•6S Visual Mgt
•RIE
ACTIVITIES• Develop Potential Solutions
• Develop Evaluation Criteria
• Select Best Solutions
• Develop Future State Process Map(s)
• Develop Pilot Plan
• Pilot Solution
• Develop Full Scale Action/
Implementation Plan
• Complete Improve Gate
1.Validate the
Problem
4. Determine Root
Cause
3. Set Improvement
Targets
5. Develop Counter-
Measures
6. See Counter-MeasuresThrough
2. IdentifyPerformance
Gaps
7. Confirm Results
& Process
8. StandardizeSuccessfulProcesses
Define Measure Analyze ControlImprove
8-STEP PROCESS
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Learning Objective
Use Lean techniques to improve the process
Understand and apply Mistake Proofing tools and techniques
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Class Exercise - Inspection
Six Sigma Black Belts are assigned to Six Sigma projects. These projects are solved by identifying, measuring, analyzing, improving, and finally controlling the measure of interest. Six Sigma Champions help stomp out barriers to ensure success. Ad hoc teams lend their process and product skills. As the defect levels fall, so does the associated cost of poor quality. Six Sigma projects deliver measurable business results. The Black Belt resource ensures the program’s success.
Purpose: To illustrate that inspection is not only Non-Value
Added but also an ineffective means to achieve quality.
Exercise: You have 60 seconds to count the letter “S” in the
paragraph below. Document your answer below.
Answer: _________
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Mistake Proofing
A poka-yoke device is any mechanism that either prevents a mistake from being made or makes the mistake obvious at a glance
Simple example – applying brake to shift transmission from “park”
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Old Process Assumptions
“Defects are inevitable, but can be caught before
leaving the organization or area (check points,
multitude of inspectors, sampling tables, SPC)”
“A disciplined, well-trained and highly motivated
employee will not make mistakes”
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Quality Goal - 99.9%
Is this Good Enough?
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Quality Goal - 99.9%
If the product were your heart, you would spend almost 9 hours a year in cardiac arrest
There would be 2 unsafe landings at Chicago a day
One hour of unsafe drinking water every 8 weeks
200,000 wrong prescriptions each year
15,000 newborn babies dropped each year
Nine missspelled words on evry page of every magazzine
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New Assumption
It is impossible to eliminate all errors
from any task performed by humans.
Indeed, inadvertent errors are both
possible and inevitable
Errors will not turn into defects if
feedback and action takes place at the
Error Stage
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Poka Yoke: What Is It?
Poka (inadvertent errors) Yokeru (avoid)
Methods for preventing mistakes becoming defects
“Quality at Source”
Can you think of an example of Poka Yoke?
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Mistake-Proofing: Conserve Electricity
Door key-card must be inserted in holder to activate electricity in room
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Forget to shake the Ketchup?
Mistake-Proofing the Ketchup lid?
H.J. Heinz did their best to keep the watery
liquid part of ketchup from soaking your bun.
Their redesigned bottle lid had a little
reservoir around the spout to catch the liquid.
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Self-check to determine if the bag is going to fit
Carry-on Luggage Mistake-Proofing
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Mistake-Proofing the ATM?
New generation ATMs perform transactions without the card leaving your hand.
Chances of leaving your card in the machine remote or impossible
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Uses of Mistake-Proofing
Enforce procedures or sequences
Signal or stop a process if a defect is created
Eliminate choices leading to incorrect actions
Prevent product or process damage
Prevent equipment damage
Prevent personal injury
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Describe the defect (or abnormality)
Identify the location at which defect occurs
Detail current standard procedures
Identify mistakes or deviations from standards
Identify conditions that provoke mistakes
Identify root cause of defect condition
Mistake proofing is significantly easier if true root cause is known
Identify type of Mistake-Proofing device required
Create the device, test and standardize
Steps in Mistake-Proofing
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Why Use Mistake-Proofing?
Why use mistake-proofing?
It works where other techniques don’t
There is lots of evidence of its effectiveness
The Poka Yoke devices tend to be inexpensive and very effective
Why is it important to CPI?
Defects are caused by errors in processes
Defects are waste and cause wasteful activities to deal with them
In a CPI operation, a defect disrupts the balance of work and the flow.
Immediate corrective action is taken to resolve the situation but, it is better to avoid this type of downtime by finding and eliminating the root cause.
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Have you ever done the following?
Driven to work and not remembered it?
Driven from work to home when you meant to stop at a store?
To Err Is Human
It happens to workers too.
Workers finish the day and don’t remember what they have done
After building “green widgets” all morning, the workers put “green parts” on the “red widgets” in the afternoon
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1. Forgetfulness
2. Misunderstanding
3. Misidentification
4. Lack of experience
5. Ignoring rules
6. Inadvertent errors
7. Slowness
8. Lack of standards
9. Surprises
10. Intentional errors
10 Types of Human Error
1. Omitted process step
2. Processing errors
3. Errors in set up of parts
4. Missing parts
5. Wrong parts
6. Processed wrong part
7. Mis-operation
8. Adjustment error
9. Errors in set up of equipment
10. Design or preparation errors in tools, jigs and fixtures
Sources of Defects10 Sources of Defects
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Judgment Inspection Involves sorting the defects out of the acceptable product,
sometimes referred to as “inspecting in quality.”
The consensus in modern quality control is that “inspecting in quality” is not an effective quality management approach.
Judgment inspection does not improve process and should be used only in the short term.
Inspection Techniques
Description
Judgment inspectionAssesses quality of production outputs or sorts out defects from good product. (e.g. inspectors)
Informative inspectionAssesses process by inspecting outputs and using information gained to control the process (a feedback loop) (e.g. SPC).
Source inspectionAssesses beforehand whether the conditions necessary for high quality production to exist (e.g. Poka Yoke).
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Exists at Source of Defect (Root Cause): Checks for factors that cause errors, not the resulting defect
100% Inspection: Uses inexpensive mistake proofing (poka-yoke) devices to inspect
automatically for errors or defective operating conditions
Immediate Action: Operations are stopped instantly when a mistake is made and not
resumed until it is rectified
Source Inspection
Never pass on a defect!
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“The old way of dealing with human error was to scold people, retrain them, and tell them to be more careful … My view is that you can’t do much to change human nature, and people are going to make mistakes. If you can’t tolerate them ... you should remove the opportunities for error.”
“Training and motivation work best when the physical part of the system is well-designed. If you train people to use poorly designed systems, they’ll be OK for awhile. Eventually, they’ll go back to what they’re used to or what’s easy, instead of what’s safe.”
“You’re not going to become world class through just training, you have to improve the system so that the easy way to do a job is also the safe, right way. The potential for human error can be dramatically reduced.”
Chappell, L. 1996. The Pokayoke Solution. Automotive News Insights, (August 5): 24i.
LaBar, G. 1996. Can Ergonomics Cure ‘Human Error’? Occupational Hazards 58(4): 48-51.
Blame the Process Not the Person
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The real question you need to ask: How are you going to detect an error?
automatic, not dependent on human attention
fail in “detect” mode
simple & low cost if possible
Setting Functions
Setting function Description
Physical
(Shingo’s contact),
Checks to insure the physical attributes of the product or process are correct and error-free (e.g. round hole).
Sequencing
(Shingo’s motion step),
Checks the precedence relationship of the process to insure steps are conducted in the correct order (e.g. check list).
Grouping or Counting
(Shingo’s fixed value methods),
Facilitate checking that matched sets of resources are available when needed or that the correct number of repetitions has occurred (e.g. egg tray).
Information enhancement
(Chase and Stewart)
Determines and ensures that information required in the process is available at the correct time and place, and that it stands out against a noisy background.
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Regulatory Function
How are you going to stop the process?
the worker needs to get the message?
By audible or visual warning
By prohibiting further processing
How are you going to eliminate the possibility of error?
The Contrapositive of Murphy’s Law
Simplicity
Symmetry
The real questions you need to ask:
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Regulatory Function
Regulatory Function
Description
Warnings Signals mistake but allows process to continue.
Gagging System shuts down.
Some resetting action required to correct the mistake.
Non-response Action leads to no response.
The process does not crash nor does it proceed.
Self-correct Process stops.
System proposes correction to mistake.
Let’s talk about it Process seeks information about what was really intended.
Teach meProcess associates correct outcomes with incorrect actions.
Co
ntr
ol M
eth
od
s
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“Hard” mistake-proofing: Designing processes and tasks to ensure error-free execution
Anticipating errors to make processes “fail-safe”
Allows for preventive actions to be part of process design
Initiating individual accountability to ensure quality work before handing off to another step in the process
“Soft” mistake-proofing: Creating alarm signals to catch defects as they occur and warn people
Andon: processes and tools to STOP the process when a problem or defect is encountered
Poka Yoke: Preventing Errors
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Level 0 (No Control): Acceptance, Inspection
Level 1 (Mitigation): Minimize Damage
Build into Inspection: for example
Double signals (sound and visual)
Cross footing in financial forms
Level 2 (Detection): Feedback and Control
Build into Process
Checks etc.
Posting Sequence
Feedback should
be immediate!
Level 3 (Avoidance):
– Build into Design
Wrong part or orientation, No fit
Forms design
Level 4 (Replacement):
– Automation or Elimination
Fail Safe
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=> provide clues about what to do:
Natural Mappings
Affordances
Visibility
Feedback
Constraints
Precise outcomes without precise knowledge or action?
Fail Safe (Cont.) Fail Safing means embedding a device or procedure in a process so
that the process will never allow a nonconformity (error) to occur.
The idea of Fail Safing is to prevent inevitable mistakes from turning
into a defect.
Fail Safing requires the ability to discriminate the good from the bad.
Simple Fail Safing methods are the low cost way to parts per million
error rate.
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Which dial turns on the burner?
Stove A
Stove B
Natural Mappings
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How would you operate these doors?
BA C
Push or pull? Left side or right? How do you know?
Affordance
Visibility means making relevant parts visible, and effectively displaying system status
Feedback means providing an immediate and obvious effect for each action taken.
Visibility and feedback
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Is Box Full or Empty?
Before Improvement
• Some boxes were unfilled
• Not found since box was
opaque
After Improvement
• Empty boxes blown off
conveyor
• Pinwheel indicates
airstream functioning
Compressed
Air
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Mistake-Proofing Examples
Redesign the process to eliminate or reduce the possibility of a particular failure mode
A way to avoid mistakes
Make the error impossible
If you cannot prevent the error, modify the process to make the error obvious (detection)
Fixture
Workpiece
Chuck
Correct Position
(can be loaded)
Wrong Position
(cannot be loaded)
Mistake-Proofing Illustrated
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Everyday Mistake-Proofing Examples
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Exercise: GGA Budgeting Recap
The Generic Government Agency (GGA) represents a government agency that is focused on obligating their budgeted dollars
GGA obligates funds by processing Budget Documents (BDs)
GGA’s ability to obtain all necessary products and services is directly related to the efficiency and effectiveness with which it processes Budget Documents
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Exercise: GGA Budget Mistake-Proofing
As a CPI Belt you have been assigned the task of Mistake Proofing the GGA Budget Document.
Brainstorm ideas on how to Mistake-Proof the document for the Generic Government Agency (IT solutions are permitted)
Put the ideas into 2 categories:
Prevention
Control/Warning
Write the ideas on flip charts and be prepared to present back to the group
20 Minutes
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Takeaways
Source Inspection
+
Mistake-Proofing
=
Zero Defects
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What other comments or questions
do you have?