Copyright © 2001-2004 Six Sigma Academy International LLC All Rights Reserved Mistake Proofing...

Copyright © 2001-2004Six Sigma Academy International LLCAll Rights Reserved

Mistake Proofing (Poka-Yoke)

Copyright © 2001- 2004Six Sigma Academy International LLCAll Rights Reserved

Mistake Proofing Pg 2

The Breakthrough Strategy®

And The Control Phase

1. Select Output Characteristic

2. Define Performance Standards

3. Validate Measurement System

4. Establish Baseline Process Capability

5. Define Performance Objectives

6. Identify Variation Sources

7. Screen Potential Causes

8. Discover Variable Relationships

9. Establish Operating Tolerances – Implement Improvements

10. Validate Measurement System

11. Determine Final Process Capability

12. Implement Process Controls

• Implement controls on the key Xs



Module Objectives

By the end of this module, the participant will be able to:

• Understand the concept of Mistake Proofing as a control method

• Apply Poka-Yoke methods as a control on identified key xs- Reduce and/or eliminate process errors from occurring- Reduce and/or eliminate process defects from occurring

• Understand “red flag” conditions

1 2 3 4 5 6 7 8 9 10 11 12D M A CI



Why Is Mistake Proofing Important?

• Improved quality and customer satisfaction

• Prevents error occurrence

• Prevents defect occurrence

• If defects occur, ensures effective action

• Little or no formal training

• Cost effective

• Easy to implement

Mistake Proofing is one of the most cost effective and reliable controls that can be used to assure that our key Xs remain at our optimum

project defined settings. It can also be used directly on the Y.



What Is Mistake Proofing (Poka-Yoke)?

• Japanese phrase: - Yokeru (to avoid), Poka (errors)

• A strategy for preventing errors in processes

• Makes it impossible for defects to pass unnoticed

• Corrects problems as soon as they are detected

• Technique detects defects

• Prevents defects from moving into next area

• Developed by Dr. Shigeo Shingo to achieve zero defects

Mistake Proof devices cannot be implemented until the key Xs needing to be controlled have been identified and settings

established (Establish Operating Tolerances, Step 11).



What’s The Secret Of Poka-Yoke?

“What’s the secret? It’s a mystery to me – Our plant is as sophisticated as you can get, yet with all this innovation at our disposal we still make defects. I can’t believe all those statistics about parts per million and zero defects coming from Japan. There must be a gimmick. With all the variability of parts coming from hundreds of vendors and going through fifty different processes with a hundred machines, it is impossible not to produce some defects. So what’s the trick? Where is thehidden weapon?”

Norman BodekPublisherPoka-Yoke, Improving Product Quality by Preventing Defects



The Secret Of Dr. Shigeo Shingo

“It is not one Poka-Yoke device, but the application of hundreds of these very simple fail-safeing mechanisms that, day after day, has brought the quality miracle to industries around the world.

Each one is relatively simple – Something you easily could do on your own. But it is the totality, the hundreds of devices, that is almost frightening to behold.”

Dr. Shigeo Shingo



• Guide pins of different sizes

• Optical magnification

• Different colored tags for pressure ranges

• Look up tables for data base entry

• Spell check

• Limit switches

• Error alarms

• Counters

• Checklists

• Asymmetric parts

• Build error checking into control logic

• Exact part count

Common Examples Of Mistake Proofing



Xdthx th xth

yj fyjdtyj______

dxrt____ rtjh

dxrtj__

d tsthy sety

drtudrtud

__________

Mistake Proofing Business Processes

• Mistake Proofing is the primary means of control for many business processes

- Check digits- Pull down menus- Check sheets- Required fields



Basics Of Mistake Proofing

Effective Mistake Proofing requires two basic concepts

• A focus on controlling the factors which cause errors – Not fixing the resulting defective output (Sigma Lean Concept)

• Inspection which is effective and tireless- This IS NOT traditional 100% inspection by inspectors- This IS a mechanical or process improvement that automatically

performs the inspection with little to no human interaction

Can not do it wrong. Can only do it one way.

If wrong, detected 100%.Can not be passed into next area.



What Does Mistake Proofing Do?

3. Output1. Input 2. Process

Ideal:

1. This process will not accept any bad parts

2. This process will not make any bad parts

3. This process will not pass on any bad parts

• The ideal process is mistake proofed at three stages:- Input - Process - Output



Error Proofing In Action

• What are the error opportunities in these everyday items?

• How have they been error proofed?

• How could they be further error proofed?



Class Exercise

Round Robin: Let’s go around the class twice.

1. The first time each participant will list a Mistake Proofing idea from one of the following:

• Home (e.g., auto shut off on flat iron)

• Auto (e.g., car won’t start unless transmission is in park/neutral)

• Sport/Recreation (e.g., dead man’s lanyard on personal watercraft)

• Amusement Parks (e.g., sensors on roller coaster tracks)

• Work/Commerce (e.g., pull down menus on forms)

• Etc.

2. The second time around, you will be asked to identify a possible Mistake Proofing for some potential vital X from your project



My New Spell Checker

Eye halve a spelling chequer It came with my pea sea

It plainly marques four my revue Miss steaks eye kin knot sea.

Eye strike a key and type a word And weight four it two say

Weather eye am wrong oar write It shows me strait a weigh.

As soon as a mist ache is maid It nose bee fore two long

And eye can put the error rite Its rare lea ever wrong.

Eye have run this poem threw it I am shore your pleased two no

Its letter perfect awl the weigh My chequer tolled me sew.



Evolution Of Defectives And Application Of Mistake Proofing

ERRORS

DEFECTS

DEFECTIVES

The Value of Mistake

Proofing



Ten Common Errors That Lead To Defects(Things That Can Cause Your Key X To Go Astray)

Errors are the cause of defects

1. Processing errors

2. Error in setting up job

3. Processing omissions

4. Assembly omissions (missing parts)

5. Inclusion of incorrect component

6. Incorrect job

7. Operation error

8. Tool or equipment error

9. Defects in job components

10. Measurement error

Consider Mistake Proofing against these having any impact on your Key Xs.

ERRORS

DEFECTS

DEFECTIVES



Human Errors That Lead To PotentialKey X Variation

1. Forgetfulness

2. Errors due to misunderstanding

3. Errors in identification

4. Errors made by untrained workers

5. Willful errors (ignore rules)

6. Inadvertent errors (distraction, fatigue)

7. Errors due to delay in decision making

8. Errors due to lack of standards

9. Surprise errors (malfunctions)

10. Intentional errors (sabotage)

Also consider Mistake Proofing against these having any impact

on your Key Xs.

ERRORS

DEFECTS

DEFECTIVES



Red Flag Condition

• What is a Red Flag condition?

• You will find that in some projects, after you have identified the Key Xs and their optimal settings, one or more of them may be extremely difficult to control. The control plan should attempt to provide robust control mechanisms, however it may be difficult to do so withoutMistake Proofing. Some examples:- Training was found to be critical, but the operation has 150% turnover- Cycle Times are very long, so the operators tend to lose concentration

and Key X breakdowns may not be observed even though gages/process measurements show the issue

Mistake Proofing is a good control application for conditions such as these.



Common Red Flag Conditions

• Frequent changes to a job

• Complex processes

• Lack of standards

• Lack of measurement systems

• Lack of training

• Long Cycle Times

• Infrequent jobs

• High output

• Environmental conditions

• Attitude (motivation)

If one of these conditions exists in your process, consider Mistake Proofing as a control for your KPIVs

e.g., Lack of Training – Establish a system where only trained operators get engraved name plaques which are placed in a clearly visible slot on the machine/work station:

Untrained operator No plaque

No plaque Management Awareness Management Awareness Action



Implementation Road Map For Mistake Proofing

Describe the defect or potential defect including the

rate

Identify where the defect is likely to occur

Analyze current tasks associated with the operation

Identify error conditions contributing to the defect

Apply Five Why analysis to the error conditions to determine

root causes

Identify (using a team approach) Mistake Proofing

strategies

Verify the efficiency of the Mistake Proofing actions

(Key X)

(Process Map)

(Process Map)

(FMEA)



Mistake Proofing Strategies

Detect defects before they move

to next step

Detect errors during processing

Prevent errors from occurring

Good Best



Optional Class Exercise

• Pick a project from your team. On a flip chart create a column of the ten common error types. Create one or more columns of defects

• Complete the matrix (next page), first identifying defects that can be caused by the errors, then brainstorm and capture Poka-Yokes for the error/defects



Optional Exercise Data Matrix

Errors

1. Processing errors2. Error in setting up job3. Processing omissions4. Assembly omissions5. Incorrect component6. Incorrect job7. Operation error8. Tool or equipment error9. Defects in job components10. Measurement error

Defect 1

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Defect 2

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Poka-Yokes

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.



Key Learning Points

•

•

•

•

•



Objectives Review

The participant will be able to:

• Communicate the concept of Mistake Proofing as a control method

• Apply Poka-Yoke methods as a control on identified key Xs- Reduce and/or eliminate process errors from occurring- Reduce and/or eliminate process defects from occurring

• Explain “Red Flag” conditions



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Copyright © 2001-2004 Six Sigma Academy International LLC All Rights Reserved Mistake Proofing...

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