Poka Yoke 减少失误 防差错技术

Parker Lean System Poka-YokeObjective•Define Poka-Yoke•Describe the purpose of Poka-Yoke•Given a work scenario, describe examples of how Poka-Yoke could be employed.•Distinguish the difference between mistake proof and fail safe•Describe the ideal approach of Poka-Yoke.•Describe characteristics of Poka-Yoke solutions.•Given examples of Poka-Yoke solutions, identify what is good and what could be improved.Poka Yoke•POKA -inadvertent error•YOKE -proof•Pronounced (POH-kah YOH-kay)In the original Toyoda Loom, Jidoka was the principle of stopping work immediately when a defect occurred. Poka Yoke was the device that made it possible.Original Toyoda Loom -JidokaSources of Defects•Inappropriate process specifications •Excessive process variability •Material properties and variability •Machine performance and variability •Inadvertent errors–Humans or machinesErrors Vs. Defects•Product defects result from errors and mistakes •Errors and mistakes will always be potential issues with operations involving people •Machines can make mistakes tooWe can achieve Zero defects by catching these errors and mistakes and preventing themfrom becoming product defectsErrors Vs. DefectsMistakes (errors) are inevitable“A human is an animal that makesmistakes”--Shingo1001 in 110-11 in 1010-21 in 10010-310-410-510-6(Highest)(Lowest)Crew reaction duringair disasterSimulated militaryemergencyPassive inspections(general walk -arounds )Monitor/inspector fails to recognize initial error by operatorSimple arithmetic errors (without re -doing calculation on separate paper)Missetting largemanual values (nostatus indication except open orclosed)Technician “seeing ”an out of calibration instrument as “intolerance ”General error of omission (no control room display)General error of omission for itemsembedded inprocedureSelection of switch dissimilar in shapeor location todesired switchMissetting large manual valves (controlled by procedure keys, chaining, etc.)Selection of key operated switch rather than non -key switch (does not include error of decision)General errors of commission (e.g., misread label and selected wrongswitch)Upper limit to credibility Two -man team (one do; one check then reverse roles)SOURSE: System Safety 2000, Joe Stephenson (New York: Van Nostrand Reinhold, 1991)Human Error RatesPoka Yoke•Makes permanent changes to equipment,operations, or procedures to eliminateopportunity for error•Provides an immediate signal if a mistakeoccursMistake Proof & Fail Safe Mistake Proof / Fail Safe techniques are partof a Poka-Yoke system•Mistake Proof –Practices and devices thatmake it easy to do it right and difficult orimpossible to do a task wrong.•Fail Safe –If anything does go wrong, itimmediately becomes impossible tocontinue (Jidoka)Ideal Function of Poka-Yoke Linkage to Jidoka and a Zero defect system •Source inspection to detect errors at theirsource•100% inspection for errors/mistakes anddefects using inexpensive sensing devices •Immediate action to stop operations when an error is detectedContact Sensors•Used to physically detect the presence or absence of an object or feature.•Used to physically detect the height orposition of a part or dimension.Impact of Poka YokeState of Defect Source Informative InspectionRegulation Impact Predicted ShutdownAnnunciationLine StopFeedback &Adjust WarningAnnunciationZero Defects (Defect Prevention)Detected Scrap & Rework(Defect Reduction)SameMistake Proof3.5 inch diskette. The diskettecannot be inserted unless it isoriented correctly. This is as faras a disk can be inserted upside-down.The beveled corner of thediskette pushes a stop in the diskdrive out of the way allowing thediskette to be inserted. Thisfeature, along with the fact thatthe diskette is not square,prohibits incorrect orientation.Mistake Proof110 volt outlets in NorthAmerica. All “grounded”items have a thirdprong that only fits oneway in the receptacle.Even two prong /ungrounded items thatare polarity sensitivecan be forced to beplugged in the sameway due to differentsized prongs on boththe plug and outlet.Here is a parts kit for an assembly operation. Can you easilytell if we have all of the right parts? Signed Packing ListMistake ProofMistake ProofThis bathroom sink has asmall hole near the top thathelps prevent overflow.This is a parts kit for an assembly operation that uses a picture. Can youtell which parts have already been installed?Mistake ProofThis automatic coffee pot is equipped with a “pause and serve ”feature. When you remove the pot, the flow isinterrupted by this simple valve.Images from John Grout: /faculty/jgrout/pokayoke.shtml Fail SafeFail SafeA special coupling on gas pumps allows the line to break away and seal if somebody drives away.Mistake Proof & Fail SafeMistake Proof & Fail SafeSki Boots and Bindings.When a skier falls and a skicomes off, a “runaway ski”can cause serious injury. SkiBrakes prevent this fromhappening by automaticallyDowndropping down when the skiboot is no longer in thebinding. They also fold upautomatically when a skiersteps into their skis.RetractedCharacteristic of PokaYoke Solutions •Simple•Inexpensive•Integral part of the process•Placed at the source of errors–Point of transformation (Process Function)•Capable of 100% inspection•Provide quick feedback–(Effective human support system in place)•Ideas generally originate on the shop floor•Prevents process or part from moving forward if errors occur.Poka Yoke Aids•Colors and color-coding •Shapes / sizes •Symbols•Other toolsDegrees of Poka-YokeIs it hard or impossible to do something wrong?•Both meet the definition of Mistake Proof•Example: Color coding doesn’t make it impossible •Impossible to do wrong is always better•Layer techniques for maximum effectLayers of Mistake ProofTrailer plug. This isthe quick disconnectelectrical connectorused to hook up thelights on a trailer to atow vehicle. Thereare two layers of MPhere: color coding(white, green, yellow& brown wires) andthe physical shape ofthe connection.What’s good? How to Improve?This form uses mistake-proofing to help the user fill out the form correctly.ExerciseBreak into teams and develop Poka Yoke devices for:•Getting to this classroom•Making sure the lights are turned off•Making sure the computers are logged off•Making sure the room is locked•Making sure the students arrive on time•Other?Remember, layers are sometimes important!Homework。