IntroductiontoPokaYokeContinuous improvement to Zero Quality Control

1、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 produ

2、ce quality product and not make a mistake or not forget sometimes.othen you really do not care to make a quality product.n address quality issues through the process.3introduction to poka yoke evolution of key “l(fā)ean” concepts1945: just in time1948: pull: withrawal by subsequent processes1953: “super

3、market” systems1947: dual machine handling, “l(fā)” 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 redu

4、ction: 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

5、 concept of “autonomation” (poka-yoke) “zero defects” concept: 1975zero quality control concept: 1977shigeo shingotoyota &taichii ohno= concepts related to poka-yoke4introduction to poka yoke contentsn introduction to poka-yoke and types of inspection systemsn poka-yoke systemsn poka-yoke method

6、sn common mistake proofing devicesn poka-yoke exercisesn shingo quiz5introduction to poka yoke poka-yoke and jidoka: simple & clearn poka-yoke: poka-yoke prevents defects from being maden jidoka: prevents defects from being passed on to the next step in the processhuman inspection human interven

7、tion 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-yoke

8、evolution toward zero quality control - operator time dedicated to continuous improvement6introduction to poka yoke three basic types of inspectionn there are three basic types of inspection techniquesojudgment inspection human, visual, possibly measured only discovers defects after productionoinfor

9、mative inspection statistical quality control: flow charts, control charts theoretical sampling techniques self check inspection, successive inspection inspects products to help control the processosource inspection process focused to correct operating conditions root causes are eliminated or correc

10、ted before 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 devi

11、ce 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

12、 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 m

13、ad 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:

14、“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

15、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

16、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

17、. 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 th

18、at 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 sprin

19、g 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 t

20、wo.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

21、 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 withspringsbu

22、ttons11introduction 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 w

23、ithspringsbuttons12introduction to poka yoke seven guidelines for poka-yoke*n quality processes - design “robust” quality processes to achieve zero defects.n utilize a team environment - leverage the teams knowledge, experience to enhance the improvement efforts.n elimination of errors - utilize a r

24、obust problem solving methodology to drive defects towards zero.n eliminate the “root cause” of the errors - use the 5 whys and 2 hs approach n do it right the first time - utilizing resources to perform functions correctly the “first” time. n eliminate non-value added decisions - dont make excuses-

25、just do it !n implement 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 excellence13introduc

26、tion 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 tim

27、e. * source: superfactory, 2003. module 6, fundamentals of manufacturing excellence14introduction to poka yoke jidokan jidoka and informative inspection( reactive approach):ncheck occurs immediately after the process step.n100% fool proof checking (no interpretation by operator in control / checking

28、 )n100% of timen although not as effective as the source inspection approach, this methodology is effective in preventing defects from being passed to next process.n it is more effective than statistical sampling and does provide feedback in reducing defects.* source: superfactory, 2003. module 6, f

29、undamentals of manufacturing excellence15introduction to poka yoke poka yoke systems govern the processn two 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” par

30、t 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 warningn control approachntakes human element out

31、 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 detectedn warning approachnsometimes an automatic shut off system is not an option.na warning or alarm system can be used to get an operators attent

32、ion.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(succ

33、essive)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)

34、18introduction to poka yoke common mistake proofing devicesn guide pins n blinking lights and alarmsn limit switches n proximity switchesn countersn checklists* source: superfactory, 2003. module 6, fundamentals of manufacturing excellence19introduction to poka yoke methods for using poka yoken poka

35、 yoke systems consist of three primary methods:1. contact2. counting3. motion-sequencen each method can be used in a control system or a warning system.n each method uses a different process prevention approach for dealing with irregularities.* source: superfactory, 2003. module 6, fundamentals of m

36、anufacturing 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 methodn a contact method functions by detecting whether a sensing device makes co

37、ntact 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 t

38、o 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 yokelighttransmit

39、terreceiverobject energy contact devicesn photoelectric switches can be used with objects that are translucent or transparent depending upon the need.n transmission method: two units, one to transmit light, the other to receive.n reflecting method:pe sensor responds to light reflected from object to

40、 detect presence.n if object breaks the transmission, the machine is signaled to shut down.* source: superfactory, 2003. module 6, fundamentals of manufacturing excellence23introduction to poka yoke contact device an example of a contact device using a limit switch. in this case the switch makes con

41、tact 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 methodsn do not have to be high tech!n passive devices are sometimes the best method. thes

42、e can be as simple as guide pins or blocks that do not allow parts to be seated in the wrong position prior to processingn take advantage of parts designed with an uneven shape!n 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 ope

43、rator right away that the part is not in proper position.* source: superfactory, 2003. module 6, fundamentals of manufacturing excellence25introduction to poka yoke counting methodn used when a fixed number of operations are required within a process, or when a product has a fixed number of parts th

44、at are attached to it. n a 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.n another approach is to count the number of parts or components required to complete an operation in advance. if operators find parts left

45、over 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 methodn the third poka yoke method uses sensors to determine if a motion or a step in a

46、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.n this method uses sensors and photo-electric devices connected to a timer. if movement does not occur when required, the switch

47、signals to stop the process or warn the operator. * source: superfactory, 2003. module 6, fundamentals of manufacturing excellence27introduction to poka yokeindicator boardmachine motion-sequence methodn in order to help operators select the right parts for the right step in a process the “sequencin

48、g” aspect of the motion-step method is used. this is especially helpful when using multiple parts that are similar in size and shape.n in 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”

49、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 devicesn sensing devices that are traditionally used in poka yoke systems can be

50、divided into three categories:1. physical contact devices2. energy sensing devices3. warning sensors n each 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 t

51、o poka yoke devices: physical contact sensorsn these devices work by physically touching something. this can be a machine part or an actual piece being manufactured. n in most cases these devices send an electronic signal when they are touched. depending on the process, this signal can shut down the

52、 operation or give an operator a warning signal.* source: superfactory, 2003. module 6, fundamentals of manufacturing excellence30introduction to poka yoke device: touch switch method: contactn used to physically detect the presence or absence of an object or item-prevents missing parts.n used to ph

53、ysically detect the height of a part or dimension.* source: superfactory, 2003. module 6, fundamentals of manufacturing excellence31introduction to poka yoke devices: energy sensorsfiber opticphotoelectricvibrationn these devices work by using energy to detect whether or not an defect has occurred.*

54、 source: superfactory, 2003. module 6, fundamentals of manufacturing excellence32introduction to poka yoke warning sensorscolor codelightsn warning sensors signal the operator that there is a problem. these sensors use colors, alarms, lights to get the workers attention !n lights: these sensors may

55、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 n dont wait for the perfect poka yoke.

56、 do it now!n if your poka yoke idea has better than 50% chance to succeeddo it!n do it now.improve later!* source: superfactory, 2003. module 6, fundamentals of manufacturing excellence34introduction to poka yoke poka yoke exercise #1 - problemn matsushita electric: industrial washing machine divisi

57、oncorrect 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 - solutionn matsushita electr

58、ic: 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 - problemn asahi national lighting companyothe upper

59、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 - solutionn asahi

60、 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 - problemn asakawa auto body