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1、,Poka-yoke and Jidoka:Continuous improvement to Zero Quality Control,Introduction to Poka Yoke,Quality and Human Error,“To err is human”Alexander PopeHuman beings make mistakes,human beings sometimes forget.If you rely on a human being to produce quality product and not make a mistake or not forget
2、sometimes.Then you really do not care to make a quality product.ADDRESS QUALITY ISSUES THROUGH THE PROCESS.,Evolution of Key“Lean”Concepts,1945:Just In Time,1948:Pull:Withrawal by subsequent processes,1953:“Supermarket”systems,1947:Dual machine handling,“L”shaped layout,1953:Work cells in“U”shaped l
3、ayouts,1950:Multi(3-4)machine handling,rectangular or“U”shaped layout,1955:Water spider concept,1962:Kanban,company wide,internal,1965:Kanban,external suppliers,1950:Andon,visual control,Set-up reduction:internal&external,1st stages of SMED:1950,Shigeo Shingo begins consulting relationship with Toyo
4、ta:1954,Inspired by Toyota“Foolproofing”measures,develops methodology to apply techniques to source inspection:1965,SMED methodology formalized:1969,1950:Fool proofing techniques and the concept of“autonomation”(Poka-yoke),“Zero Defects”concept:1975,Zero Quality Control concept:1977,Shigeo Shingo,To
5、yota&Taichii Ohno,=Concepts related to Poka-yoke,Contents,Introduction to Poka-yoke and types of inspection systemsPoka-yoke SystemsPoka-yoke MethodsCommon Mistake Proofing DevicesPoka-yoke exercisesShingo Quiz,Poka-yoke and Jidoka:Simple&Clear,Poka-yoke:Poka-yoke prevents defects from being madeJid
6、oka:Prevents defects from being passed on to the next step in the process,Human Inspection Human Intervention Mistake Proofingwith machine assist,Toll-gateInspectionat Finished Goodsor the end of main processes,In-ProcessInspectionFinal Inspection may decrease,operators may do required process inspe
7、ctions,Visual Inspection&JidokaThe beginning of autonomation-significant defect reductions,Poka-yokeEvolution toward Zero Quality Control-Operator Time dedicated to Continuous Improvement,Three Basic Types of Inspection,There are three basic types of inspection techniquesJudgment InspectionHuman,vis
8、ual,possibly measuredOnly discovers defects after productionInformative InspectionStatistical Quality Control:flow charts,control chartsTheoretical sampling techniquesSelf check inspection,Successive InspectionInspects products to help control the processSource InspectionProcess focusedTo correct op
9、erating conditionsRoot causes are eliminated or correctedBefore production occurs,Will notreduce defects,A Short Story Yamada Electric,Nagoya,Japan,The 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,Mat
10、sushita 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 th
11、e 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.Matsu
12、shita 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?”,A Short Story Yamada Electric,Nagoya,Japan,The Consultant and the Plant Manager:C:“What does it mea
13、n 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 firs
14、t 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,
15、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
16、and incorporate it into your process.”,Question:Have you ever forgotten anything?,A Short Story Yamada Electric,Nagoya,Japan,The 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 ou
17、t 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.,A Shor
18、t Story Yamada Electric,Nagoya,Japan,The 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.
19、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 dis
20、h after assembly,the worker realized that a spring had been left out,and the assembly was corrected.,A Short Story Yamada Electric,Nagoya,Japan,The 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 plac
21、es button on switch.Operator packs.Box is ready for shipment.,Seven Guidelines for Poka-yoke*,Quality Processes-Design“Robust”quality processes to achieve zero defects.Utilize a Team Environment-leverage the teams knowledge,experience to enhance the improvement efforts.Elimination of Errors-Utilize
22、a robust problem solving methodology to drive defects towards zero.Eliminate the“Root Cause”of The Errors-Use the 5 Whys and 2 Hs approach Do It Right The First Time-Utilizing resources to perform functions correctly the“first”time.Eliminate Non-Value Added Decisions-Dont make excuses-just do it!Imp
23、lement an Incremental Continual Improvement Approachimplement improvement actions immediatelyfocus on incremental improvementsefforts do not have to result in a 100%improvement immediately.,*Source:Superfactory,2003.Module 6,Fundamentals of Manufacturing Excellence,Poka yoke,Poke-yoke and Point of O
24、rigin Inspections(Proactive Approach):A fully implemented zero defect system requires Poka yoke usage at or before the inspection points during the process.Poka yoke will catch the errors before a defective part is manufactured 100%of the time.,*Source:Superfactory,2003.Module 6,Fundamentals of Manu
25、facturing Excellence,Jidoka,Jidoka and Informative Inspection(Reactive Approach):Check occurs immediately after the process step.100%fool proof checking(no interpretation by operator in control/checking)100%of TimeAlthough not as effective as the Source inspection approach,this methodology is Effect
26、ive in preventing defects from being passed to next process.It is more effective than statistical sampling and does provide feedback in reducing defects.,*Source:Superfactory,2003.Module 6,Fundamentals of Manufacturing Excellence,Poka yoke Systems Govern the Process,Two Poka Yoke System approaches a
27、re utilized in manufacturing which lead to successful zero defect systems:1.Control ApproachShuts down the process when an error occurs.Keeps the“suspect”part in place when an operation is incomplete.2.Warning ApproachSignals the operator to stop the process and correct the problem.,*Source:Superfac
28、tory,2003.Module 6,Fundamentals of Manufacturing Excellence,Control versus Warning,CONTROL APPROACHTakes human element out of the equation;does not depend on an operator or assembler.Has a high capability of achieving zero defects.Machine stops when an irregularity is detected,WARNING APPROACHSometi
29、mes an automatic shut off system is not an option.A warning or alarm system can be used to get an operators attention.Below left is an example of an alarm system using dials,lights and sounds to bring attention to the problem.Color coding is also an effective non automatic option.,Poka-yoke and Jido
30、ka,Inspection Method,Source InspectionPoka-yoke-Proactive,Informative Inspection(successive)Jidoka-Reactive,Informative Inspection(self)Jidoka-Reactive,Setting Function,Regulative Function,Common Mistake proofing Devices,Guide Pins Blinking lights and alarmsLimit switches Proximity switchesCountersC
31、hecklists,*Source:Superfactory,2003.Module 6,Fundamentals of Manufacturing Excellence,Methods for Using Poka yoke,Poka yoke systems consist of three primary methods:1.Contact2.Counting3.Motion-SequenceEach method can be used in a control system or a warning system.Each method uses a different proces
32、s prevention approach for dealing with irregularities.,*Source:Superfactory,2003.Module 6,Fundamentals of Manufacturing Excellence,Missing cylinder;piston fully extended,alarm sounds,Contact Method using limit switches identifies missing cylinder.,Cannot proceed to next step.,Cylinder present,Contac
33、t Method,A contact method functions by detecting whether a sensing device makes contact with a part or object within the process.An 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
34、 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 Excellence,Limit Switches,Toggle Switches,Physical Contact Devices,*Source:Superfactory,2003.Module 6,Fundamentals of Manufacturing Excel
35、lence,Light,Transmitter,Receiver,Object,Energy Contact Devices,Photoelectric switches can be used with objects that are translucent or transparent depending upon the need.Transmission method:two units,one to transmit light,the other to receive.Reflecting method:PE sensor responds to light reflected
36、from object to detect presence.If object breaks the transmission,the machine is signaled to shut down.,*Source:Superfactory,2003.Module 6,Fundamentals of Manufacturing Excellence,Contact Device,An example of a contact device using a limit switch.In this case the switch makes contact with a metal bar
37、b sensing its presence.If no contact is made the process will shut down.,*Source:Superfactory,2003.Module 6,Fundamentals of Manufacturing Excellence,Contact Methods,Do not have to be high tech!Passive devices are sometimes the best method.These can be as simple as guide pins or blocks that do not al
38、low parts to be seated in the wrong position prior to processingTake advantage of parts designed with an uneven shape!A 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.,*Sou
39、rce:Superfactory,2003.Module 6,Fundamentals of Manufacturing Excellence,Counting Method,Used 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.A sensor counts the number of times a part is used or a process is comple
40、ted and releases the part only when the right count is reached.Another 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:Super
41、factory,2003.Module 6,Fundamentals of Manufacturing Excellence,Motion-Sequence Method,The 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 t
42、he machine and signal the operator.,This 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 Excellence,Indicator Boa
43、rd,Machine,Motion-Sequence Method,In 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.In this example,each step of the machine
44、 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 Excellence,Types of S
45、ensing Devices,Sensing devices that are traditionally used in poka yoke systems can be divided into three categories:1.Physical contact devices2.Energy sensing devices3.Warning Sensors Each category of sensors includes a broad range of devices that can be used depending on the process.,*Source:Super
46、factory,2003.Module 6,Fundamentals of Manufacturing Excellence,Devices:Physical Contact Sensors,These devices work by physically touching something.This can be a machine part or an actual piece being manufactured.In most cases these devices send an electronic signal when they are touched.Depending o
47、n the process,this signal can shut down the operation or give an operator a warning signal.,*Source:Superfactory,2003.Module 6,Fundamentals of Manufacturing Excellence,Device:Touch Switch Method:Contact,Used to physically detect the presence or absence of an object or item-prevents missing parts.Use
48、d to physically detect the height of a part or dimension.,*Source:Superfactory,2003.Module 6,Fundamentals of Manufacturing Excellence,Devices:Energy Sensors,Fiber optic,Photoelectric,Vibration,These devices work by using energy to detect whether or not an defect has occurred.,*Source:Superfactory,20
49、03.Module 6,Fundamentals of Manufacturing Excellence,Warning Sensors,Color Code,Lights,Warning sensors signal the operator that there is a problem.These sensors use colors,alarms,lights to get the workers attention!Lights:These sensors may be used in conjunction with a contact or energy sensor to ge
50、t the operators attention.,Lights connected to Micro switches&timers,*Source:Superfactory,2003.Module 6,Fundamentals of Manufacturing Excellence,3 Rules of POKA YOKE,Dont wait for the perfect POKA YOKE.Do it now!If your POKA YOKE idea has better than 50%chance to succeedDo it!Do it now.improve later
