1Introduction to Poka YokePoka-yoke and Jidoka: Continuous improvement to Zero Quality ControlIntroduction to Poka Yoke2Introduction to Poka Yoke Quality and Human Errorn“To err is human” Alexander PopeoHuman beings make mistakes, human beings sometimes forget.oIf you rely on a human being to produce quality product and not make a mistake or not forget sometimes.oThen you really do not care to make a quality product.nADDRESS QUALITY ISSUES THROUGH THE PROCESS.3Introduction to Poka Yoke Evolution of Key “Lean” Concepts1945: Just In Time1948: Pull: Withrawal by subsequent processes1953: “Supermarket” systems1947: Dual machine handling, “L” shaped layout1953: Work cells in “U” shaped layouts1950: Multi (3-4) machine handling, rectangular or “U” shaped layout1955: Water spider concept1962: Kanban, company wide, internal1965: Kanban, external suppliers1950: Andon, visual control Set-up reduction: internal & external, 1st stages of SMED: 1950Shigeo Shingo begins consulting relationship with Toyota: 1954Inspired by Toyota “Foolproofing” measures, develops methodology to apply techniques to source inspection: 1965SMED methodology formalized: 19691950: Fool proofing techniques and the concept of “autonomation” (Poka-yoke) “Zero Defects” concept: 1975Zero Quality Control concept: 1977Shigeo ShingoToyota &Taichii Ohno= Concepts related to Poka-yoke4Introduction to Poka Yoke ContentsnIntroduction to Poka-yoke and types of inspection systemsnPoka-yoke SystemsnPoka-yoke MethodsnCommon Mistake Proofing DevicesnPoka-yoke exercisesnShingo Quiz5Introduction to Poka Yoke Poka-yoke and Jidoka: Simple & ClearnPoka-yoke: Poka-yoke prevents defects from being madenJidoka: Prevents defects from being passed on to the next step in the processHuman Inspection Human Intervention Mistake Proofingwith machine assist Toll-gateInspectionat Finished Goodsor the end of main processesIn-ProcessInspectionFinal Inspection may decrease, operators may do required process inspectionsVisual Inspection&JidokaThe beginning of autonomation - significant defect reductions Poka-yokeEvolution toward Zero Quality Control - Operator Time dedicated to Continuous Improvement6Introduction to Poka Yoke Three Basic Types of InspectionnThere are three basic types of inspection techniquesoJudgment InspectionHuman, visual, possibly measuredOnly discovers defects after productionoInformative InspectionStatistical Quality Control: flow charts, control chartsTheoretical sampling techniquesSelf check inspection, Successive InspectionInspects products to help control the processoSource InspectionProcess focusedTo correct operating conditionsRoot causes are eliminated or correctedBefore production occursWill notreduce defects7Introduction to Poka Yoke A Short Story Yamada Electric, Nagoya, JapanThe Plant manager:“One of the operations we do involves the assembly of an extremely simple push-button device that we deliver to our parent company, Matsushita Electric. The device is composed of two buttons, and on button and an off button, under each of which we have to enclose a small spring. Sometimes, though, one of our workers forgets to put in a spring. When Matsushita electric discovers a switch without a spring, we have to send an inspector all the way to Kyusha to check every switch that was delivered.This is a real pain in the neck, so whenever it happens, we tell workers to be particularly careful and for a while things improve a bit. The same thing happens again before long, though, and these chronic defects are getting to be a nuisance. Matsushita gets mad at us every time for making mistakes in such a simple operation, and I recently had to go to Kyusha myself to apologize. Is there anything we can do to keep these defects from happening?”8Introduction to Poka Yoke A Short Story Yamada Electric, Nagoya, JapanThe Consultant and the Plant Manager:C:“What does it mean for a human being to forget something?”PM: The plant manager looked puzzled “To forget means well it just means to forget something, doesnt it?”When the Consultant asked the Plant Manager to explain, he was unable to answer. So he suggested to him that there were really two kinds of forgetting. The first involves simply forgetting something. Since people are not perfect, they will, on rare occasions, simply forget something. It is not intentional, it just happens.C:“The second type of forgetting, involves forgetting that one has forgotten. We are all familiar with this kind of forgetting. It is the reason, for example, that we make checklists for ourselves. You can apply the same thing to this operation, rather than thinking that your people should assemble switches perfectly, every time, you should recognize that being human, they will, on rare occasions forget things. Why not take the idea of the checklist and incorporate it into your process.”Question: Have you ever forgotten anything?9Introduction to Poka Yoke A Short Story Yamada Electric, Nagoya, JapanThe Current State:The operator assembles two switches at a time, places the finished switches into a box that holds one hundred. Before shipping, a QC inspector pulls a sample out of every box. The Solutions:1. The operator assembles two switches at a time, places the finished switches into a rack that hold only six, after completing six, pushes each button on each of the six to check to see if the spring is there. After pushing the buttons, the operator packs into the box.Box withSpringsButtonsBox withSpringsButtons10Introduction to Poka Yoke A Short Story Yamada Electric, Nagoya, JapanThe Solutions:2. In the first motion, an operator inserts two springs in the switch then moves them to operator two.Operator two inspects that the spring is in place, then places the cover on the switch, places the finished switches into a box that holds one hundred.Before shipping, a QC inspector pulls a sample out of every box.3. The operator has a small bowl in front of her.In her first motion she takes two springs from the box, places them in a dish.In her second motion, she inserts the spring and then the buttons are installed.If any spring remained on the dish after assembly, the worker realized that a spring had been left out, and the assembly was corrected. Box withSpringsButtonsBox withSpringsButtons11Introduction to Poka Yoke A Short Story Yamada Electric, Nagoya, JapanThe Solutions:4. The button is designed so that it cannot be installed unless the spring is present in the switch.Operator installs two springs.Operator places button on switch.Operator packs.Box is ready for shipment.Box withSpringsButtons12Introduction to Poka Yoke Seven Guidelines for Poka-yoke*nQuality Processes - Design “Robust” quality processes to achieve zero defects.nUtilize a Team Environment - leverage the teams knowledge, experience to enhance the improvement efforts.nElimination of Errors - Utilize a robust problem solving methodology to drive defects towards zero.nEliminate the “Root Cause” of The Errors - Use the 5 Whys and 2 Hs approach nDo It Right The First Time - Utilizing resources to perform functions correctly the “first” time. nEliminate Non-Value Added Decisions - Dont make excuses-just do it !nImplement an Incremental Continual Improvement Approachoimplement improvement actions immediatelyofocus on incremental improvementsoefforts do not have to result in a 100% improvement immediately.* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence13Introduction to Poka Yoke Poka yokenPoke-yoke and Point of Origin Inspections (Proactive Approach):nA fully implemented zero defect system requires Poka yoke usage at or before the inspection points during the process.nPoka yoke will catch the errorsn before a defective part is manufacturedn 100% of the time. * Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence14Introduction to Poka Yoke JidokanJidoka and Informative Inspection( Reactive Approach):nCheck occurs immediately after the process step.n100% fool proof checking (no interpretation by operator in control / checking )n100% of TimenAlthough not as effective as the Source inspection approach, this methodology is Effective in preventing defects from being passed to next process.nIt is more effective than statistical sampling and does provide feedback in reducing defects.* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence15Introduction to Poka Yoke Poka yoke Systems Govern the ProcessnTwo Poka Yoke System approaches are utilized in manufacturing which lead to successful zero defect systems:1. Control ApproachoShuts down the process when an error occurs.oKeeps the “suspect” part in place when an operation is incomplete.2. Warning ApproachoSignals the operator to stop the process and correct the problem.* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence16Introduction to Poka Yoke Control versus WarningnCONTROL APPROACHnTakes human element out of the equation; does not depend on an operator or assembler.n Has a high capability of achieving zero defects.n Machine stops when an irregularity is detectednWARNING APPROACHnSometimes an automatic shut off system is not an option.nA warning or alarm system can be used to get an operators attention.nBelow left is an example of an alarm system using dials, lights and sounds to bring attention to the problem.nColor coding is also an effective non automatic option.17Introduction to Poka Yoke Poka-yoke and JidokaInspection MethodSource InspectionPoka-yoke - ProactiveInformative Inspection(successive)Jidoka - ReactiveInformative Inspection(self)Jidoka - ReactiveSetting FunctionContact MethodMotion-Sequence MethodConstant Value MethodCounts parts or operation steps.Regulative FunctionControl MethodStops the ProcessWarning MethodAlarm or Light tells operator totake action (eg: stop machine)18Introduction to Poka Yoke Common Mistake proofing DevicesnGuide Pins nBlinking lights and alarmsnLimit switches nProximity switchesnCountersnChecklists* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence19Introduction to Poka Yoke Methods for Using Poka yokenPoka yoke systems consist of three primary methods:1. Contact2. Counting3. Motion-SequencenEach method can be used in a control system or a warning system.nEach method uses a different process prevention approach for dealing with irregularities.* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence20Introduction to Poka YokeMissing cylinder;piston fully extended, alarm soundsContact Method using limit switches identifies missing cylinder.Cannot proceed to next step.Cylinder present Contact MethodnA contact method functions by detecting whether a sensing device makes contact with a part or object within the process.oAn example of a physical contact method is limit switches that are pressed when cylinders are driven into a piston. The switches are connected to pistons that hold the part in place. In this example, a cylinder is missing and the part is not released to the next process.* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence21Introduction to Poka YokeLimit SwitchesToggle Switches Physical Contact Devices* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence22Introduction to Poka YokeLightTransmitterReceiverObject Energy Contact DevicesnPhotoelectric switches can be used with objects that are translucent or transparent depending upon the need.nTransmission method: two units, one to transmit light, the other to receive.nReflecting method:PE sensor responds to light reflected from object to detect presence.nIf object breaks the transmission, the machine is signaled to shut down.* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence23Introduction to Poka Yoke Contact DeviceAn example of a contact device using a limit switch. In this case the switch makes contact with a metal barb sensing its presence. If no contact is made the process will shut down.* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence24Introduction to Poka Yoke Contact MethodsnDo not have to be high tech!nPassive devices are sometimes the best method. These can be as simple as guide pins or blocks that do not allow parts to be seated in the wrong position prior to processingnTake advantage of parts designed with an uneven shape!nA work piece with a hole a bump or an uneven end is a perfect candidate for a passive jig. This method signals to the operator right away that the part is not in proper position.* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence25Introduction to Poka Yoke Counting MethodnUsed when a fixed number of operations are required within a process, or when a product has a fixed number of parts that are attached to it. nA sensor counts the number of times a part is used or a process is completed and releases the part only when the right count is reached.nAnother approach is to count the number of parts or components required to complete an operation in advance. If operators find parts leftover using this method, they will know that something has been omitted from the process.* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence26Introduction to Poka Yoke Motion-Sequence MethodnThe third poka yoke method uses sensors to determine if a motion or a step in a process has occurred. If the step has not occurred or has occurred out of sequence, the sensor signals a timer or other device to stop the machine and signal the operator.nThis method uses sensors and photo-electric devices connected to a timer. If movement does not occur when required, the switch signals to stop the process or warn the operator. * Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence27Introduction to Poka YokeIndicator BoardMachine Motion-Sequence MethodnIn order to help operators select the right parts for the right step in a process the “sequencing” aspect of the motion-step method is used. This is especially helpful when using multiple parts that are similar in size and shape.nIn this example, each step of the machine cycle is wired to an indicator board and a timer. If each cycle of the machine is not performed within the required “time” and “sequence”, the indicator light for that step will be turned on and the machine will stop.* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence28Introduction to Poka Yoke Types of Sensing DevicesnSensing devices that are traditionally used in poka yoke systems can be divided into three categories:1. Physical contact devices2. Energy sensing devices3. Warning Sensors nEach category of sensors includes a broad range of devices that can be used depending on the process.* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence29Introduction to Poka Yoke Devices: Physical Contact SensorsnThese devices work by physically touching something. This can be a machine part or an actual piece being manufactured. nIn most cases these devices send an electronic signal when they are touched. Depending on the process, this signal can shut down the operation or give an operator a warning signal.* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence30Introduction to Poka Yoke Device: Touch Switch Method: ContactnUsed to physically detect the presence or absence of an object or item-prevents missing parts.nUsed to physically detect the height of a part or dimension.* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence31Introduction to Poka Yoke Devices: Energy SensorsFiber opticPhotoelectricVibrationnThese devices work by using energy to detect whether or not an defect has occurred.* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence32Introduction to Poka Yoke Warning SensorsColor CodeLightsnWarning sensors signal the operator that there is a problem. These sensors use colors, alarms, lights to get the workers attention !nLights: These sensors may be used in conjunction with a contact or energy sensor to get the operators attention.Lights connected to Micro switches & timers* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence33Introduction to Poka Yoke 3 Rules of POKA YOKE nDont wait for the perfect POKA YOKE. Do it now!nIf your POKA YOKE idea has better than 50% chance to succeedDo it!nDo it now.improve later!* Source: Superfactory, 2003. Module 6, Fundamentals of Manufacturing Excellence34Introduction to Poka Yoke Poka Yoke Exercise #1 - ProblemnMatsushita Electric: Industrial Washing Machine DivisionCorrect water level is critical to the package-sealing machine.Operator visually checks water level 4X per shift.Instances of inadequate water levels have occurred.ValveWater lineAcceptable water levelWhat would you do?35Introduction to Poka Yoke Poka Yoke Exercise #1 - SolutionnMatsushita Electric: Industrial Washing Machine DivisionInadequate water volume activates a water level sensor and a valve opens automatically to supply water.Approximate cost: $150Water lineWater-level sensorsValve36Introduction to Poka Yoke Poka Yoke Exercise 2 - ProblemnAsahi National Lighting CompanyoThe upper and lower “boxers” staple the box closed.oOccasionally the bottom stapler “misses”.oSince cases continue to move along the line, it is especially difficult to verify the presence of a staple on the bottom of the box.What would you do?37Introduction to Poka Yoke Poka Yoke Exercise 2 - SolutionnAsahi National Lighting CompanyoA sensor to detect staples was mounted at the rear of the packaging machine.oThis sensor, linked to a counter, verifies the number of staples and sends a signal to the “stopper” to stop the cases if a staple is missed.38Introduction to Poka Yoke Poka Yoke Exercise 3 - ProblemnAsakawa Auto Body IndustriesoIn a two step process, workers would first drill holes in a board set, then take the board set and spot weld it.oOccasionally the operators would forget to drill all of the holes required.oAfter spot welding, the piece could not be reworked if it was missing holes.Multi-spotMachineDrillFlowWhat would you do?39Introduction to Poka Yoke Poka Yoke Exercise 3 - SolutionnAsakawa Auto Body IndustriesoThe welder and drill were linked.oSimple hole sensors were installed on the drill machine.oThe spot welder would not operate unless all holes were detected.FlowDrillMulti-spotMachine40Introduction to Poka YokeMulti-spotMachineDrillDrillMulti-spotMachine41Introduction to Poka YokeOnOffOnOff42Introduction to Poka Yoke Shigeo ShingonZero Quality Control: Source Inspection and the Poka-yoke System43Introduction to Poka Yoke Shingo Quiz1. Which of the following is not one of the inspection techniques identified by Shingo: A. Source B. Informative C. Statistical D. Judgment 2. Judgment Inspection: A. is a very effective inspection technique B. reduces defect rates dramatically C. used solely to discover defects after production D. should be used whenever possible 44Introduction to Poka Yoke Shingo Quiz3. A setting function: A. is a very effective inspection technique B. signals that a defect has occurred C. keeps a machine from operating when defects are likely to be produced D. is the link between inspection and the regulatory function 4. A regulatory function: A. is the remedial action taken after a process goes out-of-controlB. signals that a defect has occurred C. keeps a machine from operating when defects are likely to be produced D. B or C 45Introduction to Poka Yoke Shingo Quiz5. Source Inspection: A. reduces defect rates dramaticallyB. used solely to sort out defects after productionC. should be avoided D. both A & B 6. Which is not an informative inspection technique: A. statistical process controlB. acceptance samplingC. successive-checksD. self-checks 46Introduction to Poka Yoke Shingo Quiz7. The correct ranking of Shingos inspection techniques (from best to worst) is: A. judgment, informative, sourceB. source, judgment, informativeC. informative, source, judgmentD. source, informative, judgment 8. Informative Inspection: A. inspects products to help control the processB. inspects process to help control the productC. keeps a machine from operating when defects are likely to be producedD. should be avoided 47Introduction to Poka Yoke Shingo Quiz9. Poka-Yoke: A. replaces any quality system you are currently usingB. can reduce or eliminate human errorC. cannot be used to reduce process varianceD. is only used for source inspection 48Introduction to Poka Yoke Shingo Quiz1. Which of the following is not one of the inspection techniques identified by Shingo: A. Source B. Informative C. Statistical D. Judgment 2. Judgment Inspection: A. is a very effective inspection technique B. reduces defect rates dramatically C. used solely to discover defects after production D. should be used whenever possibleC: Shingo identified 3 inspection techniques: judgement, informative, sourceC: Is used solely to discover defects after production.49Introduction to Poka Yoke Shingo Quiz3. A setting function: A. is a very effective inspection technique B. signals that a defect has occurred C. keeps a machine from operating when defects are likely to be produced D. is the link between inspection and the regulatory function 4. A regulatory function: A. is the remedial action taken after a process goes out-of-controlB. signals that a defect has occurred C. keeps a machine from operating when defects are likely to be produced D. B or C D: A setting function detects when the inspection outcome is not acceptable and invokes the regulatory functionD: A regulatory function is an attention-getting signal (a buzzer, warning light or machine stoppage) that something is wrong. It can indicate a defect has just been made (in self-checks) or that it is about to be made (in source inspections).50Introduction to Poka Yoke Shingo Quiz5. Source Inspection: A. reduces defect rates dramaticallyB. used solely to sort out defects after productionC. should be avoided D. both A & B 6. Which is not an informative inspection technique: A. statistical process controlB. acceptance samplingC. successive-checksD. self-checksA: Source inspection checks the process for correct operating conditions before production occurs. The known causes of defects are either eliminated or corrected before production can create defects. B: Successive-checks, self checks and statistical process control are all informative inspection techniques. They provide information to help control the process. Acceptance sampling is used to infer whether a lot or shipment should be rejected 51Introduction to Poka Yoke Shingo Quiz7. The correct ranking of Shingos inspection techniques (from best to worst) is: A. judgment, informative, sourceB. source, judgment, informativeC. informative, source, judgmentD. source, informative, judgment 8. Informative Inspection: A. inspects products to help control the processB. inspects process to help control the productC. keeps a machine from operating when defects are likely to be producedD. should be avoided D: Source inspection is the best because it prevents defects. Informative inspection help control the process but may allow defects to occur. Judgment inspection is the worst since it only sorts out defects. A: Inspects products to help control the process 52Introduction to Poka Yoke Shingo Quiz9. Poka-Yoke: A. replaces any quality system you are currently usingB. can reduce or eliminate human errorC. cannot be used to reduce process varianceD. is only used for source inspection B: Human error is not easily detected using control charts because errors tend to be relatively rare and intermittent. Mistake-proofing (poka-yoke) can be an effective response to human error. 53Introduction to Poka Yoke Shingo Quiz: How did you do?All 9 correct = YOU are a GURU! 7 or 8 correct = Approaching zero defects - continue to improve. 5 or 6 correct = Cpk