Introduction_to_Poka_YokeContinuous improvement to Zero Quality Control.ppt

,poka-yoke and jidoka: continuous improvement to zero quality control,introduction to poka yoke,quality and human error,“to err is human” alexander pope human 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 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 layouts,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 toyota: 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,toyota & taichii ohno,= concepts related to poka-yoke,contents,introduction to poka-yoke and types of inspection systems poka-yoke systems poka-yoke methods common mistake proofing devices poka-yoke exercises shingo quiz,poka-yoke and jidoka: simple & clear,poka-yoke: poka-yoke prevents defects from being made jidoka: prevents defects from being passed on to the next step in the process,human inspection human intervention mistake proofing with machine assist,toll-gate inspection at finished goods or the end of main processes,in-process inspection final inspection may decrease, operators may do required process inspections,visual inspection & jidoka the beginning of autonomation - significant defect reductions,poka-yoke evolution toward zero quality control - operator time dedicated to continuous improvement,three basic types of inspection,there are three basic types of inspection techniques judgment inspection human, visual, possibly measured only discovers defects after production informative inspection statistical quality control: flow charts, control charts theoretical sampling techniques self check inspection, successive inspection inspects products to help control the process source inspection process focused to correct operating conditions root causes are eliminated or corrected before production occurs,will not reduce 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, 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?”,a short story yamada electric, nagoya, japan,the 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?,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 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.,a short 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. 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.,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 places 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 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 ! implement an incremental continual improvement approach implement improvement actions immediately focus on incremental improvements efforts 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 origin 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 manufacturing 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 time although not as effective as the source inspection approach, this methodology is effective 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 are utilized in manufacturing which lead to successful zero defect systems: 1. control approach shuts down the process when an error occurs. keeps the “suspect” part in place when an operation is incomplete. 2. warning approach signals the operator to stop the process and correct the problem.,* source: superfactory, 2003. module 6, fundamentals of manufacturing excellence,control versus warning,control approach takes 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 approach sometimes 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 jidoka,inspection method,source inspection poka-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 alarms limit switches proximity switches counters checklists,* source: superfactory, 2003. module 6, fundamentals of manufacturing excellence,methods for using poka yoke,poka yoke systems consist of three primary methods: 1. contact 2. counting 3. motion-sequence each method can be used in a control system or a warning system. each method uses a different process 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,contact 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 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 excellence,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 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 barb 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 allow parts to be seated in the wrong position prior to processing take 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.,* source: 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 completed 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: superfactory, 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 the 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 board,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 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 sensing devices,sensing devices that are traditionally used in poka yoke systems can be divided into three categories: 1. physical contact devices 2. energy sensing devices 3. warning sensors 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 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 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 excellence,device: touch switch method: contact,used to physically detect the presence or absence of an object or item-prevents missing parts. used 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, 2003. 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 get 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!,* source: superfactory, 2003. module 6, fundamentals of manufacturing excellence,poka yoke exercise #1 - problem,matsushita electric: industrial washing machine division correct water level is critical to the package-sealing machine. operator visually checks water level 4x per shift. instances of inadequate water levels have occurred.,what would you do?,poka yoke exercise #1 - solution,matsushita electric: industrial washing machine division inadequate water volume activates a water level sensor and a valve opens automatically to supply water. approximate cost: $150,poka yoke exercise 2 - problem,asahi national lighting company the upper and lower “boxers” staple the box closed. occasionally the bottom stapler “misses”. since 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?,poka yoke exercise 2 - solution,asahi national lighting company a sensor to detect staples was mounted at the rear of the packaging machine. this 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.,poka yoke exercise 3 - problem,asakawa auto body industries in a two step process, workers would first drill holes in a board set, then take the board set and spot weld it. occasionally the operators would forget to drill all of the holes required. after spot welding, the piece could not be reworked if it was missing holes.,flow,what would you do?,poka yoke exercise 3 - solution,asakawa auto body industries the welder and drill were linked. simple hole sensors were installed on the drill machine. the spot welder would not operate unless all holes were detected.,flow,shigeo shingo,zero quality control: source inspection and the poka-yoke system,shingo quiz,1. 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,shingo quiz,3. 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 th