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  1. 1. i LIST OF CONTENTS TITLE PAGE NO. 1. INTRODUCTION 1 1.1 Overview 1 1.2 What Is Poka-Yoke? 2 1.3 Need Of Poka-yoke 3 1.4 Technical Aspects Of Poka-Yoke Method 4 1.5 When To Use It? 6 2. COMMON DEVICES USED IN POKA-YOKE SYSTEMS 7 3. TYPES OF POKA-YOKE 10 3.1 Poka-yoke Methods 10 3.1.1 Shut down Method 10 3.1.2 Prevention Method 10 3.1.3 Control Method 11 3.2 How To Use It? 11 4. METHODOLOGY OF POKA-YOKE 12 4.1 Methods 12 4.2 Methods Of Obtaining Poka-Yoke 14 5. EXAMPLES AND CASE STUDIES OF POAK-YOKE 15 5.1 Examples Of Poka-Yoke 15 5.1.1 Alarm Systems 15 5.1.2 Connector And Charger 15 5.1.3 Finger Print Identification 16 5.1.4 Dialysis Machine 17
  2. 2. ii 5.2 Case Study of Poka-Yoke 18 6. CHALLENGES AND LIMITATIONS OF POKA-YOKE 22 6.1 Challenges Of Poka-yoke 22 6.2 Characteristics Of Poka-Yoke 22 6.3 Qualities Of Good Poka-Yoke 23 7. CONCLUSION 24 8. REFERENCES 24
  3. 3. iii LIST OF FIGURES TITLE PAGE NO. 1.1 USB Cable 1 1.2 Cost and Zero defects relationship 4 2.1 Sensing object interrupts light 8 2.2 Vibration sensor 8 4.1 Poka-Yoke system design 13 5.1 Alarm Systems 15 5.2 connector and charger 16 5.3 Finger print Identification device 16 5.4 Dialysis machine 17 5.5 Poka-Yoke simple practical implementation 18 5.6 Location of metal chips and punching location 19
  4. 4. iv ABSTRACT In today’s competitive world any organization has to manufacture high quality, defect free products at optimum cost. The new culture of total quality management, total productive management in the manufacturing as well as service sector gave birth to new ways to improve quality of products. By using various tools of TQM like KAIZEN, Six Sigma, JIT, JIDCO, POKA YOKE, FMS etc. organization is intended to develop quality culture. During actual manufacturing of any product there are too many simple and smonotonous steps which are carried out by operators. These monotonous work operations result in to mental fatigue and lack of interest in work which ultimately causes silly mistakes of operators and we know that human is prone to errors even though he doesn’t want it. To avoid these simple mistakes, poka yoke concept play important role. By implementing some simple solutions we can avoid mistakes. The long term success of poka yoke gives output of saving time and we release the work pressure on mind of worker. We can use creativity and special skills of workers for more creative operations instead of increasing pressure for monotonous activities
  5. 5. POKA-YOKE 132U1A0479 Page 1 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore CHAPTER- 1 INTRODUCTION 1.1 Overview: Nowadays, each and every company wants profit, high productivity, value in market. There are slogans in most factories stating defect reduction targets, but the ultimate aim should always be zero defects. "POKA-YOKE" is a vital factor in eliminating defects. Poka-yoke is a concept in total quality management which is related to restricting errors at source itself. It deals with "fool-proofing" or "mistake-proofing". A poka-yoke is any idea generation or mechanism development in a total productive management process that helps operator to avoid (yokeru) mistakes (poka). Main aim of Poka Yoke concept is to make whole system error proof that means no one can make mistake although some one wants to make mistake sin tentionally. It eliminates the defects or faults. This term was coined by Shigeo Shingo in 1960sfor the part of Toyota Production System. The aim of Poka-yoke is to design the process so that mistakes can be detected and corrected immediately, eliminating defects at the source. A methodical approach to build up Poka-Yoke countermeasures which consists in a three step analysis of the risks to be managed: 1. Identification of the need 2. Identification of possible mistakes 3. Management of mistakes before satisfying the need. These steps are taken into consideration while thinking about implementation of Poka Yoke system in any field because this methodology remains same at all the situations and conditions. Figure 1.1: USB cable Above figure 1.1 shows the concept of the Poka Yoke system. In upper diagram, size of both holes are same, therefore there may be mistake of putting positive terminal into negative hole but
  6. 6. POKA-YOKE 132U1A0479 Page 2 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore on the other hand, in lower figure, the sizes of both the holes are different which results in avoiding the misplacement of the terminal into wrong hole. 1.2 What is POKA-YOKE? Poke-yoke (Mistake proofing) is a Japanese improvement strategy for mistake-proofing to prevent defects (or Nonconformities) from arising during manufacturing processes. Poka-yoke is a preventive action that focuses on identifying and eliminating the special causes of variation in manufacturing processes, which inevitably lead to product defects or nonconformities. This concept was initially called Idiot Proofing but it was understood that this name may heart workers so term Mistake Proofing was coined by Shigeo Shingo. Poka-yoke gives a strategy and policy for preventing defects at the source. Poka-yoke solutions are not only the cost-effective but also easy to understand and apply. Mistake proofing is one of the important tools to add to any organization’s Continuous improvement. In short poka-yoke is a continual improvement strategy that offers a way to move the QMS (quality management system) towards a higher level of performance. The poka- yoke(mistake proofing) concept was generated in the mid-1960s by Shigeo Shingo who is Japanese industrial engineer. Shingo was working for the Toyota and other Japanese companies, where he developed entire Manufacturing systems focused on achieving zero defects in production and gave birth to this revolutionary work. The basic concept behind poka- yoke(mistake proofing) is that it is not acceptable and allowed to produce even a small amount of nonconforming product. To stay in market and to become a whole world-class competitor, an organization must go with new strategy and technology along with side by side practice of producing zero defects. Poka-yoke methods are the easy and simple concepts for achieving this goal and are a key component of the continual improvement strategy in many leading Japanese companies on this moment. Poka-yoke (fool proofing) is one of the presentations of “good kaizen”, or superior continual improvement because of its preventive nature. A poka yoke device or solution is apply any mechanism or idea that either avoids the mistake from being made or makes the mistake easily identify at a glance. The ability to find mistakes at a glance is important because, as Shingo states, "The causes of defect lie in workers errors, and defects are the results of neglecting those errors. It follows that mistakes will not turn into defects if worker errors are discovered and eliminated beforehand"[Shingo 1986. He also adds to this that "Defects arise
  7. 7. POKA-YOKE 132U1A0479 Page 3 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore because errors are made” the two have a cause-and-effect relationship. Yet errors will not turn into defects if feedback and action take place at error stage During actual manufacturing of any product there are too many very simple and monotonous steps which are carried out by operators. These are monotonous work operations result in to mental fatigue and lack of interest in work which ultimately causes silly mistakes of operators and we know that human is prone to errors even though he doesn’t want it. To avoid these simple mistakes by poka-yoke concept play important role. By implementing some simple solutions we can avoid mistakes. The long term achievement of poka- yoke gives output of saving time and we release the work pressure on mind of worker. We can use creativity and innovative skills of workers for more creative operations instead of increasing pressure for monotonous activities This involvement of everyone in organization is basic need to rise roots of quality culture in the organization. 1.3 Need of POKA-YOKE When any organization decides to implement the lean manufacturing then one of the objective is to reduce scrap because no one is interested to compensate extra inventory on account of scrap. As per philosophy of lean manufacturing it focuses on speed of production and productivity also. In order to follow this concept of speed we should prevail against defects and rework. To the increase profit percentage the cost pressures always become headache for top management so they never accept continued mistakes like scrap, rework, lateness etc. out of tolerance instead they are aiming to achieve value of zero in this segment. When customers of any company buys product they rightfully expect defect free products and conventional 100% inspection or statistical process control don’t insure 100% defect-free products (zero defect). Hence we are going to root cause of any problem and avoiding it which gives us defect free product. In the above discussion concludes that to get defect free products one should go with the concept of Poka-Yoke. Below graph plotted between cost/defects.
  8. 8. POKA-YOKE 132U1A0479 Page 4 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore Fig 1.2: cost& zero defects relation 1.4 Technical aspect of Poka-Yoke method Poka-Yoke technique can be applied both to prevent causes, which will result in subsequent occurrences of errors and to carry out inexpensive control determining whether to adopt or reject the product. It is not always 100% probability elimination of all errors, in such cases it is the task of Poka-Yoke methods is detection as soon as possible. Analyze the process of product defects formation noted that between a mistake resulting from the defect is yet one, the potential possibility: The observation mistake and its correct. It is therefore the proposal -method for reducing defective is planning conditions in which error may not happen, or will be immediately visible and captured. Take into account the above Shigeo Shingo developed a achieving "zero defects" in industrial conditions, i.e. in such a way as simple and cheap. Was itself at the matter, that it is not possible to reduce the defects using random checks. It is necessary to the total control - 100% control. Shigeo Shingo adopted assumptions like in the case of confusion applying the statistical process control is ineffective, monitoring and control the poka-yoke should be autonomous, i.e. operations carried out by the contractor without intervention from the outside, 100% - the total, cheap. Shigeo Shingo has analyzed in detail the process formation of defects and errors from the source to effect. He said that mistake from the producer becomes defect for the user in this moment when the customer unnoticed this defect. It should be therefore a maximum reduced and speed up action coupling back, and so on as soon as possible –and simplest should be detect errors (inspection of information, "after the fact", typical for statistical control). 1. At the earliest as soon as possible signal error before it become the defect (in the
  9. 9. POKA-YOKE 132U1A0479 Page 5 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore 2. Eliminate possibility of the occurrence error (inspection at source, verify the conditions under which runs the operation in order to eliminate the possibility formation error). The Poka-Yoke is a technique for avoiding human error at work. A defect exists in either of two states; the defect either has already occurred, calling for defect detection, or is about to occur, calling for defect prediction. Poka-yoke has three basic functions to prevent or reduce defects: shutdown, control, and warning. Categories of poka-yoke devices Poka-yoke devices fall into two major categories: prevention and detection. A prevention device engineers the process so that it is impossible to make a mistake at all. A classic example of a prevention device is the design of a 3.5 inch computer diskette. The diskette is carefully engineered to be slightly asymmetrical so that it will not fit into the disk drive in any orientation other than the correct one. Prevention devices remove the need to correct a mistake, since the user cannot make the mistake in the first place. A detection device signals the user when a mistake has been made, so that the user can quickly correct the problem. The small dish used at the Yamada Electric plant was a detection device; it alerted the worker when a spring had been forgotten. Detection devices typically warn the user of a problem, but they do not enforce the correction. We are surrounded every day by both detection and prevention poka-yoke devices, though we may not usually think of them as such. My microwave will not work if the door is open (a prevention device). My car beeps if I leave the key in the ignition (a detection device). At few years ago, some cars were designed not to start until the passengers had buckled their seat belts (a prevention device); but this mechanism was too intrusive and was replaced by a warning beep (a detection device).
  10. 10. POKA-YOKE 132U1A0479 Page 6 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore 1.5 When to use it? Poka-yoke can be used wherever something can go wrong or an error can be made. It is a technique, a tool that can be applied to any type of process be it in manufacturing or the service industry. Errors are many types – 1.Processing error : Process operation missed or not performed per the standard operating procedure. 2. Setup error: Using the wrong tooling or setting machine adjustments incorrectly. 3. Missing part: Not all parts included in the assembly, welding, or other processes. 4. Improper part/item: Wrong part used in the process. 5. Operations error :Carrying out an operation incorrectly; having the incorrect version of the specification. 6. Measurement error: Errors in machine adjustment, test measurement or dimensions of a part coming in from a supplier.
  11. 11. POKA-YOKE 132U1A0479 Page 7 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore CHAPTER-2 COMMON DEVICES USED IN POKA-YOKE SYSTEMS The common devices used in Poka –Yoke systems are: 1. Guide pin 2. Blinking light and Alarms 3. Limit Switches 4. Proximity switches(sensor) Guide pin: Guide pins are often used as a means of ensuring the accuracy with which machined parts are stacked on top of one another. They may also be used as a means of correctly aligning one component of a two-part system with the other. The pin may actually come in the form of a bolt with a tapered end or even in the shape of a bullet with the corresponding piece containing metal or plasticized grommets at every contact point. The grommets would allow the guide pins to penetrate the secondary component in order to ensure the accurate configuration of the two parts being put together. Blinking light and alarm: Modular design with sturdy housing for all indoor and outdoor applications in tough conditions wherever machine status needs to be displayed and warning signals given. Limit Switch: A limit switch is an electromechanical device that consists of a actuator mechanically linked with a set of contacts. When any object comes into contact with the actuator, the device operates the contacts to make or break an electrical connection. Limit switches are used in a different type of applications and environments because of their ruggedness, ease of installation, and reliability of operation. Limit Switch can determine the presence / absence, passing, positioning, and end of travel of an object. Limit switch were first used to define the limit of travel of an object; hence the name "Limit Switch".
  12. 12. POKA-YOKE 132U1A0479 Page 8 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore Sensor: A sensor is a transducer whose purpose is to sense (that is, to detect) some characteristic of its environs. It detects events or changes in quantities and provides a corresponding output, generally as an electrical or optical signal; for example, a thermocouple converts temperature to an output voltage. But a mercury-in-glass thermometer is also a sensor. Sensing device are traditionally used in poka-yoke i. Physical contact device ii. Energy sensing device (a) Photo electric Sensor The transmitter and receiver of the thru-beam sensor and housed in different cases that are separated from each other the Emitter(E) Transmits directly to the receiver(R). If object(O) interrupt the light beam, the receiver voltage drop and the switching function is initiated. The thru-beam sensor are used to monitor production and packing lines to measure full state in transparent container or as a safety measure for door and hazardous area. Fig2.1 : Sensing object interrupts the light (b)Vibration sensor Despite the advances made in vibration monitoring and analysis equipment, the selection of sensors and the way they are mounted on a machine remain critical factors in Fig2.2 : Vibration sensor determining the success of any monitoring program. Money saved by installing inferior sensors is not a prudent investment since the information provided about the machine of interest often is
  13. 13. POKA-YOKE 132U1A0479 Page 9 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore not accurate or reliable. Poor quality sensors can easily give misleading data or, in some cases, cause a critical machine condition to be completely overlooked.
  14. 14. POKA-YOKE 132U1A0479 Page 10 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore CHAPTER-3 TYPES OF POKA- YOKE 3.1 poka yoke methods: The Poka-Yoke is an innovative technique for to keep away human error at work. A defect or imperfection exists in either of two states; the defect either has already occurred in that case calling for defect detection, or is about to occur in that case calling for defects prediction. The technique starts by analyzing the process for potential problems, identifying parts by the characteristics of dimension, shape & size and weight, detecting process deviation from nominal procedures and norms. Depending on the basic functionality Poka-yoke has three types 1. Shutdown Poka yoke 2. Control Poka yoke 3. Warning Poka yoke Shutdown (Prevention) Method In shut down i.e. prevention method Poka-yoke devices checks critical process parameters and shut down the process when a situation moves out of the tolerance zone, it is indicates of a defective product has either been produced or is about to be produced. That is well known note that prevention is always better than cure. By implementing shutdown method we can assure about 100% defect free products. It has 0 % chances to produced defective products, up to this level we can reliance on it. E.g. Use of fuse in the electric circuit. When there is an short circuit then fuse is operated and cut down the supply of electricity resulting in avoiding any further accidents. Control method In control method Poka-yoke devices are regulatory in working which are installed on process equipment and/or Work pieces which make it impossible to produce defects and/or to flow a nonconforming product to the next process. As like shut down is an method control method gives 100% defect free products. The control make certainty that if there is any defect, it is not coming outside the production line and does not reach to the customer. E.g. To avoid any wrong job loading in reverse direction on machine we can provide work rest for the job which will avoid wrong job loading.
  15. 15. POKA-YOKE 132U1A0479 Page 11 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore Warning (Alert) method This is the method which makes the operator conscious about something is going wrong. The Mechanism or simple idea is generated in such a way that Poka-yoke devices indicate or shows to a worker that a defect has been produced. When operators get such warning then he must immediately interfere the process to correct the process (es) responsible for causing the defect. In case of irresponsible behavior of operator irrespective of getting warning notice the next products will continue the same defect and produce nonconforming products. In short again warning (alert) method depends on human nature and behavior. It is concluded that alert method gives 30% of the guarantee of good products. Actually warning method tells about existence of defect but does not assure and does not produce 100% quality. The common warning method are use of blinking light and use of beeping sound as alarm alert. e.g. Beeping sound or flashing of light in ATM machine after removing ATM card from machine to warn operator that he is safe and ensure that card is not in machine. Once top management decides to implement TPM culture in organization then to compensate for defect free products successfully one should follow the methodology of Poka-yoke. 3.2 HOW TO USE IT ? Step by step process in applying poka-yoke: 1. Identify the operation or process 2. Analyse and understand the ways in which a process can fail. 3. Decide the right Poka-yoke approach, such as using a,  Shut out Type: Preventing an error being made, or an  Attention Type: Highlighting that an error has been made. 4. Determine whether a  Contact Method  Constant Number or Counting Method  Motion-Sequence Method 5. Trial the method and see if it works. 6. Train the operator, review performance and measurement success.
  16. 16. POKA-YOKE 132U1A0479 Page 12 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore CHAPTER-4 METHODOLOGY OF POKA-YOKE The methodology of poka-yoke are: 1. Identify Problem 2. Observation at workstation 3. Brainstorming for idea 4. Select best idea 5. Implementation Plan and Implementation 6. Monitor and sign off Step 1: Identify problem In this stage the complaints coming from the customers (Both internal and external customer) are collected. The principle of standard is determined by considering various criteria’s like number of complaints from the customer& PDI( pre dispatch classify), the quantity of defects detected by quality control, materiality defects (their impact on the customer, costs, implemented process) and then data is collected broadly. As per analysis all results of the collected data company plans for developing poka yoke system for the selected problem. In this way in first stage the problem is selected. Step 2 :Observation at work stations In this step the actual on site study of the problem is carried out. The causes behind the problem are sort out by using fishbone diagram (fishbone diagram is cause and effect diagram given by Japans management guru Ishikawa).The causes may be related to man skill, machine, material or method accordingly the complete sorting is carried out. Step 3: Brainstorming for Idea This is a technique to capture all creativity and skills of employee’s .In brainstorming session the problem under study is put forward to committee. Then study problem given by all members and give various solutions to avoid that defect. As each person has one uniqueness this step concludes with various alternative solutions for same problem.
  17. 17. POKA-YOKE 132U1A0479 Page 13 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore Step 4: Select best ideas After getting all various alternative solutions it is time to select best one out of all collected solutions. Criteria for selection may be cost, problem create after installation, time required, changes in existing system, opportunity to develop new solutions, simplicity in operation etc. By referring all selection criteria’s committee concludes With one best solution. Step 5: Implementation plan and implementation This step is concerned with implementation planning& installation. It deals with material requirement, processing the material and finally manufactured mechanism is implemented at actual working site. Step 6: Monitoring and sign off The produced products are checked for defects under study also the performance of poka yoke system is also monitored and project is shut downed. Fig-4.1Poka-Yoke System design
  18. 18. POKA-YOKE 132U1A0479 Page 14 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore 4.2 Methods Of Obtaining Poka Yoke Poka yoke ideas are simple but creative in operation and generation. According to Shingo "Defects will never be reduced if the workers involved do not modify operating methods when defects occur." Following are some of the simple ideas (hints) to avoid mistakes: 1) Using Shapes and Colours 2) Software Warnings and Reminders 3) Using Dialogue Boxes and Software Checks 4) Using Switches and Automatic Braking 5) Using Checklists 6) Visual Prevention Methods 7) Using Lights, Sounds, Signs and Barriers Etc.
  19. 19. POKA-YOKE 132U1A0479 Page 15 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore CHAPTER-5 EXAMPLES AND CASE STUDIES OF POKA YOKE 5.1 Examples: 5.1.1 Alarm Systems They are activated with alarms for security purposes. If an unauthorized person enters the bank, or the electric circuit of the door bell catches fire, a warning alarm rings, which ensures that you can take care of the problem before it gets out of hand. Fig 5.1 Alarm systems 5.1.2 Connector and charger The figure shows a charger and connector. All the three pins need to fit perfectly within the three slots provided. This has to be monitored during production. And for that, the design phase of the product needs to be executed perfectly as well. A slight error in the calculation of the slot-size or the pin-size can make the device redundant or faulty.
  20. 20. POKA-YOKE 132U1A0479 Page 16 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore Fig 5.2: Connector and charger 5.1.3 Fingerprint Identification This is used extensively in biometrics, forensics, detective agencies, etc. Every fingerprint in the world is unique, no two are ever the same. The device is such that only the Fig5.3 : Finger print identification device fingerprint of that particular person will be required as input. Trying to replicate or use some one's fingerprint forcibly will not work either.
  21. 21. POKA-YOKE 132U1A0479 Page 17 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore 5.1.4 Dialysis machine These machines perform the function of the kidneys and are used for patients suffering from CKD (Chronic Kidney Disorder). An example of a safety device in this machine is the efficient design of the air bubble detector. This detector must be fully functional and should ensure that no air bubble passes to the patient's body. If this occurs, the patient may have seizures and this can prove fatal. Hence, the detector must be equipped with a proper mechanism to find out the problem, and give out beeps so that proper action can be taken immediately. Fig 5.4 Dialysis machine They are many examples of poka yoke as follows:  Spindle of CNC machine starts only after closing the safety door. If door is open then machine will not run. It is shut down poka yoke to avoid accidents.  The guide pins are used in stamping dies for correct alignment of upper and lower portion. If there is improper matching assembly of dies will not take place. It is shut down poka yoke.  If we want to close any file in operating software (e.g. Microsoft Word) it asks for save it or cancel dialogue box. This is warning system against by mistake closing of file. It is warning poka yoke.  To avoid parallax error in reading the measuring instrument small mirror is placed below the moving pointer. By referring pointer and its mirror image we can take proper reading. It is warning poka yoke.  The socket for USB on the computer is designed in such a way that we can’t connect pen drive or any corresponding pin in opposite or wrong way. It is control poka yoke system.
  22. 22. POKA-YOKE 132U1A0479 Page 18 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore 5.2 Case studies Problem: - Job loading in reverse direction causing job rejection, damage to tool and machine geometry Aim:- To ensure correct loading of job Ideas After Brain Storming:-When problem is taken on the table of brainstorming the following options are obtained for above mentioned problem  Use of proximity sensor to detect reverse loading of job.  Use of photo sensor.  Instructions to operator.  Separate fixtures to keep the incoming job to enable operator to load the job correctly.  Painting the correct and wrong end of job with different colors.  Use of color sensors to differentiate between correct and wrong end of job.  To provide work rest for the job.  To provide mechanical stopper. Etc. From the analysis of various solutions the meeting concludes that they should go with last option i.e. to provide mechanical stopper. Fig 5.5 Poka yoke simple practical implementation Now they will plan for implementing the selected solution and monitor for the result and switch over to next problem. Problem Statement: The problem in this case was missing metal clips. That component which was to be punch sometimes sent further for punching operation without conforming all metal Clips are there its place or not. These were results in wastage of time which indirectly affect productivity of the plant.
  23. 23. POKA-YOKE 132U1A0479 Page 19 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore Fig 5.6: Location of metal clips and Punching Location From chart 1, we can conclude that in each lot of50 components, we found 2 to 3 components such that metal clips were missed so if we calculate total PPM of the readings, we get that it was too high which leads to wastage of so much time. Fig 5.7 : Number of Defects/ 50 Components (6 lots)
  24. 24. POKA-YOKE 132U1A0479 Page 20 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore Problem Solution: There is a very smart solution to this problem which is expressed in circuit diagram below. The main task we have to do is to stop the air flow from the compressor to pneumatic cylinder if any one of the metal clip is missing. Lots No. Of Samples Missed Clips Components PPM (Before) PPM (After) 1 50 2 40000 0 2 50 1 20000 0 3 50 0 0 0 4 50 1 20000 0 5 50 4 80000 0 6 50 3 6000 0 Avg 300 11 36666.6 0 TABLE 1:Results after poka yoke method
  25. 25. POKA-YOKE 132U1A0479 Page 21 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore Fig 5.8: Result Before and After From above table and chart we can see the result we obtained after implementation of the Poka Yoke concept to the punching machine.
  26. 26. POKA-YOKE 132U1A0479 Page 22 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore CHAPTER-6 CHALLENGES AND LIMITATIONS OF POKA YOKE 6.1 Challenges of Poka-yoke As per up till discussion in the paper it seems that poka yoke is one of the best tool in total quality management but we have to think about the obstacles and challenges against poka yoke. Some of challenges are listed below-  Practical implementation of the mechanism or solution is not possible.  Process parameters don’t allow changing the existing system.  Sometimes the poka yoke is not cost effective.  Interdepartmental relations between production and quality department are not good so each one think that I don’t have to do anything with that issue.  Now also we are depending on statistical process control.  Expert advice is needed for new creative and challenging tasks .It may happen that experts are not available with small scale industries and expert advice is not economical for their financial health. 6.2 Characteristics of good poka-yoke devices Good poka-yoke devices, regardless of their implementation, share many common characteristics :  They are simple and cheap. If they are too complicated or expensive, their use will not be cost- effective.  They are part of the process, implementing what Shingo calls "100%" inspection.  They are placed close to where the mistakes occur, providing quick feedback to the workers so that the mistakes can be corrected.  Judged by these criteria, the "small dish" solution to the missing-spring problem is an excellent poka-yoke device:  It was simple.  It was cheap, involving only the cost of a small dish.  It provided immediate feedback about the quality of the work; corrections could be made on the spot.
  27. 27. POKA-YOKE 132U1A0479 Page 23 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore 6.3 Qualities of a Good Poka Yoke A good Poka Yoke must meet the following qualities:  Early: A good poka yoke must be early in the process, so that it can provide quick feedback -- and help in detecting mistakes the moment they occur.  Precise: It should be precise, so that it is easy to diagnose and identify what mistake occurred.  Simple: The poka yoke should be simple -- to develop and maintain. This is quite important since one doesn’t want to spend time and effort in maintaining poka yokes, and complex poka yokes will have a fairly high chance of becoming erroneous. Having a buggy poka yoke is worse than having no poka yoke at all.  Light: The poka yoke needs to be unobtrusive and transparent. If a poka yoke itself becomes an overhead to the process, then it will drive the developers/users crazy, and they will find ingenious ways to avoid it all together. For instance, think about how a developer will feel if he/she has to run a 70 minute pre-commit script before each and every check-in!
  28. 28. POKA-YOKE 132U1A0479 Page 24 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore CHAPTER-7 CONCLUSION To err is human nature so we can’t blame human being for each and every mistake. As like err, Intelligence is also human nature so we can dominate preceding nature by next nature. Poka yoke is just a face of that intelligence. We can avoid the mistakes at the source itself by using above mentioned methodology. About mistake proofing we can say that it is a system for organizing work that eliminates any chances of error by new user also. It also allow user to function without mistake or prevent error that are about to occur. In order to implement quality management system successfully each activity should aim towards excellence. Poka yoke is one of the most important tool in TQM(Total Quality Management). Successful poka yoke results in increased productivity with minimum waste (waste due to rework, scrap) because we are sure about the quality of product, as mistakes are blocked at source itself. There may be some practical limitations in poka yoke but we have to overcome all that for achieving the aim of “Zero Defects, Zero Waste and Zero Delays”. In one sentence poka yoke is launching preventive actions for systematic movement on the success ladder of QMS(Quality Management System) with higher level of performance and productivity of system with high quality products at minimum cost.
  29. 29. POKA-YOKE 132U1A0479 Page 25 GEETHANJALIINSTITUTE OF SCIENCE AND TECHNOLOGY Gangavarm(v), kovur(M), Nellore CHAPTER-8 REFERENCES 1. Anil S. Badiger, R. Gandhinathan, V. N. Gaitonde, Rajesh S. Jangaler “Implementation of Kaizen and Poka-yoke to Enhance Overall Equipment Performance - A case study” 2. Ivan Fantin (2014). Applied Problem Solving. Method, Application, root causes, countermeasures, Poka-Yoke and A3. How to make things happen to solve problems. 3. John R. Grout, and Brian T. Downs; “A Brief Tutorial on Mistake-proofing, Poka- Yoke, and ZQC”; Lean Business Solutions United States 4. John R. Grout, and Brian T. Downs; “A Brief Tutorial on Mistake-proofing, Poka- Yoke, and ZQC”; Lean Business Solutions United States 5. MrParikshit S. Patil; MrSangappa P. Parit; Mr. Y.N. Burali “Poka Yoke: The Revolutionary Idea In Total Productive Management” 6. Pratik D. Tak, Shravan S. Wagh “Poka Yoke Implementation On Punching Machine: A Case Study” 7. Patel Parikshit K, Vidya Nair, Patel Nikunj S “A Review on use of Mistake Proofing (Poka Yoke) Tool in Blow Molding Process” 8. M. Dudek-Burlikowska, D. Szewieczek “The Poka-Yoke method as an improving quality tool of operations in the process” 9. Shinto S., Zero Quality Control: Source Inspection and the Poka– Yoke System,