6.2 mistake proofing

8/12/2019 6.2 Mistake Proofing

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EIN 6935 /4933LEAN Six Sigma

Instructor: Christos Nicolaou

6.2 MISTAKE PROOFING


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Learning Objectives

What is Mistake-Proofing (or Poka-Yoke)Reasons for Human Error

Mistake-Proofing Methods


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To err is human Mistake or Error is somethingdone incorrectly.Defect is when an error ormistake is not prevented ordetected and it escapes to next

operation, or worse by far, toour end customer.The ques t ion i s : How can w eprevent e r rors and m is takes

o r s t o p t h em f r o m b e c o m i n gdefec ts?

DEFECTS are the result of ERRORS

ERRORS are the cause of DEFECTS

Reasons for Human Error

Lack of knowledge, skills,or abilityMental errorsSensory overloadMechanical process errorsDistractionsLoss of memory

Loss of emotional control


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Mistake-Proofing (or Poka-Yoke)Using ingenuity to create devices that allow us to do our job100% error free 100% of the time.

Make them simple Make them inexpensive Design for prompt feedback Design for preventive action Focus on the application Input from right peopleEven in the best systems there are chances for errors ormistakes.

A Simple Idea Can Be a Great Way toMistake-Proof a Problem


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Mistake Proofing Works Well Where: Worker vigilance is needed (manual operations) Mis-positioning can occur. Adjustment is required. SPC is difficult to apply or ineffective. Attributes, not measurements, are important. Training cost and employee turnover are high. Mixed model production occurs.

Users make mistakes and blame the service provider. Special causes reoccur. Field failures are extremely expensive.


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Everyday Examples of Mistake-Proofing The Sneak a Cup feature on coffee brewers. Beeper on ATMs so that we wont forget card. We cant shift from park unless brake pedal is depressed. Kill switch on treadmills.

Picture on bill changer to insert bill correctly. KittingSeven day medicine/pill dispensers Lock-out fields and tab control on electronic forms

We Often Take It for Granted, but Mistake-Proofing Is All Around Us


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ELIMINATION REPLACEMENT PREVENTION FACILITATION DETECTION

MITIGATION


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ELIMINATION seeks to eliminate thepossibility of error by redesigning the productor process so that the task or part is no longernecessary.

Product simplification or part consolidation thatavoids a part defect or assembly error in the firstplace.

Eliminate decisions and steps.


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Mistake-Proofing Methods - ELIMINATION

Air baffles needed to beattached to cover to direct

airflow over hot components.

Adhesive could come loose ifnot properly applied.

Baffle also prone to damageduring assembly.

Alternative design has bafflefunction stamped into sheet metal

cover eliminating troublesomeassembly step.


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REPLACEMENT substitutes a more reliableprocess to improve consistency.

Automatic dispensers or applicators to insure thecorrect amount of a material such as an adhesive

is applied.


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PREVENTION engineers the product orprocess so that it is impossible to make amistake at all.

Part features that only allow assembly the correctway

Unique connectors to avoid misconnecting wireharnesses or cables

Part symmetry that avoids incorrect insertion


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Mistake-Proofing Methods - PREVENTION

Two-door and four-door models areproduced on this line.

The fixture is built so that it isimpossible to put a four-door part inplace when the fixture is set-up for a

two-door model and vice-versa.

Notice the limit switch in center-right which helps insure proper

orientation.If correct part is turned backward or

upside down, it will not fit.


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FACILITATION employs techniques andcombining steps to make work easier toperform.

Visual controls including color coding, marking orlabeling parts to facilitate correct assembly

A staging tray that provides a visual control that allparts were assembled, locating features on parts


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Mistake-Proofing Methods - FACILITATION

Board orientation onbottom row 180

different from top row.

Color coded boardinsertion screws andpanel color-coding

facilitate correct boardorientation for insertion.


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DETECTION involves identifying an errorbefore further processing occurs so that theuser can quickly correct the problem.

Sensors in the production process to identify whenparts are incorrectly assembled, built-in self-testcapabilities in products.


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Mistake-Proofing Methods - DETECTION

A conveyor carries theproduct under a pivoting flag.

A correctly assembled

product passes under theflag.

An incorrectly assembledproduct tips the flag, and a

sensor detects the flagmovement.


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MITIGATION seeks to minimize the effects oferrors.

Fuses to prevent overloading circuits resulting fromshorts

Products designed with low-cost, simple reworkprocedures when an error is discovered

Extra design margin or redundancy in products to

compensate for the effects of errors


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Mistake-Proofing Methods - MITIGATION


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Mistake-ProofingIdeally, mistake-proofing should beconsidered during thedevelopment of a

new product tomaximizeopportunities to

mistake-proof throughdesign of the productand the process.


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Mistake-Proofing Attitude

If it can be done wrong,it will be!

Mistakes can beeliminated!

One mistake out thedoor is one too many!

Mistake-Proofing Can Help Us BecomeMore Competitive!


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Poka Yoke: MistakeProofing ~ 2:26 mins

http://www.youtube.com/watch?v=2RthkxGwFsU&feature=player_detailpage
http://www.youtube.com/watch?v=2RthkxGwFsU&feature=player_detailpagehttp://www.youtube.com/watch?v=2RthkxGwFsU&feature=player_detailpagehttp://www.youtube.com/watch?v=2RthkxGwFsU&feature=player_detailpagehttp://www.youtube.com/watch?v=2RthkxGwFsU&feature=player_detailpage


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Class Participation

Name some mistake proofing methodsand/or devices

6.2 mistake proofing

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