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Poka yoke

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Mistake proofing

Publicado en: Empresariales, Tecnología
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Poka yoke

  1. 1. May 26, 2012 1
  2. 2. INTRODUCTIONWhat is a Poka- yoke? Shigeo shingo defined poka-yoke as POKA- ‘Inadvertent mistake that anyone can make’ and YOKE- ‘To prevent or proof’ Poka-yoke is a tool to have “zero defects” and even reduce or eliminate quality control. Poka-yoke is a Japanese name for “fool-proofing”. Poke-yoke represents the intelligence of the operator by excluding repetitive actions that require a thinking process. May 26, 2012 2
  3. 3. MISTAKE PROOFING Mistake-Proofing a products design and its manufacturing process is a key element of design for manufacturability / assembly (DFM/A) Mistake proofing is also a key element of improving product quality and reliabilityFACTORS CONTRIBUTING TO MISTAKE PROOFING: Attention Perception Memory Logical reasoning May 26, 2012 3
  4. 4. PRINCIPLES OF MISTAKE-PROOFING There are six mistake-proofing principles or methods. Elimination seeks to eliminate the possibility of error by redesigning the product or process so that the task or part is no longer necessary. Replacement substitutes a more reliable process to improve consistency. Prevention engineers the product or process so that it is impossible to make a mistake at all. Facilitation employs techniques and combining steps to make work easier to perform. Detection involves identifying an error before further processing occurs so that the user can quickly correct the problem. Mitigation seeks to minimize the effects of errors. May 26, 2012 4
  5. 5. 2-STATUS & 3-FUNCTIONS OF POKA-YOKE POKA-YOKE HAS 2 STATUS AND 3 FUNCTIONS:  Status: 1.The fault will happen or 2.The fault has happened  Functions: 1.Stop 2.Check or 3.AlarmMay 26, 2012 5
  6. 6. THREE STRATEGIES FOR ZERO DEFECT Only make the product when required! Make the product so it can not be used for anything else. If the product is ready use it immediately. May 26, 2012 6
  7. 7. POKA-YOKE CLASSIFICATION Poka-yoke is classified into the following types: Server Poka-Yokes Customer Poka-Yokes Task Preparation Encounter Treatment Tangibles ResolutionMay 26, 2012 7
  8. 8. PROVIDER(SERVER) ERRORS Task Errors • Doing the work incorrectly • Doing work not requested • Doing work in the wrong order • Doing work too slowly Treatment Errors • Not acknowledging the customer • Not listening to the customer • Not reacting appropriately to the customer Tangible Errors • Failure to clean facilities • Failure to control noiseMay 26, 2012 8
  9. 9. CUSTOMER ERRORS Preparation Errors • Failure to bring necessary materials to the encounter • Failure to engage the correct service Encounter Errors • Failure to remember steps in the service process • Failure to follow system flow • Failure to follow instructions Resolution Errors • Failure to learn from experience • Failure to adjust expectations appropriately May 26, 2012 9
  10. 10. SEVEN STEPS TO POKA-YOKE ATTAINMENT Quality Processes Utilize a team environment Elimination of Errors Eliminate the “Root Cause” of The Errors Do It Right The First Time Eliminate Non-Value Added Decisions Implement a Continual Improvement ApproachMay 26, 2012 10
  11. 11. POKA-YOKE APPROACH Proactive Approach : A fully implemented ZERO DEFECT QUALITY 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. Reactive Approach : Check occurs immediately after the process. Can be an operator check at the process or successive check at the next process. Not 100% effective, will not eliminate all defects. Effective in preventing defects from being passed to next process. May 26, 2012 11
  12. 12. Two Poka-Yoke System approaches are utilized in manufacturing which lead to successful ZERO DEFECT QUALITY: 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.May 26, 2012 12
  13. 13. CONTROL SYSTEM 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. May 26, 2012 13
  14. 14. WARNING SYSTEMS Sometimes an automatic shut off system is not an option. A warning or alarm system can be used to get an operators attention. Color coding is also an effective non-automatic option May 26, 2012 14
  15. 15. TEN TYPES OF HUMAN MISTAKES  Forgetfulness  Mis-understanding  Wrong identification  Lack of experience  Willful (ignoring rules or procedure)  Inadvertent or sloppiness  Slowliness  Lack of standardization  Surprise (unexpected machine operation, etc.)  Intentional (sabotage)May 26, 2012 15
  16. 16. POKA-YOKE DEVICES Poka yoke is implemented by using simple objects like fixtures, jigs, warning devices and the like to prevent people from committing mistakes, even if they try to!. The main feature of poka-yoke devices is their exceptional suitability for reducing or eliminating defects through effective feedback and instantaneous corrective action. These devices are capable of being used all the time by all workers; simple and usually installed with low implementation cost. Poka-yoke devices help eliminate errors and defects by giving machines the “intelligence” to stop and signal when a error occurs. Poka-yoke devices stop machines and alert workers when a problem exists. May 26, 2012 16
  17. 17. THE THREE LEVELS OF POKA-YOKE: There are three levels at which your company can effect poka- yoke: Eliminating errors defects and losses at the source or prevention of a mistake from being committed.. Detection of a loss or mistakes it occurs,allowing correction before it becomes a problem. Detection of a loss or mistakes after it has occurred,just in time before it blows up into a major issue(least effective).May 26, 2012 17
  18. 18. EXAMPLES OF POKA-YOKE PRODUCTSMay 26, 2012 18
  19. 19. May 26, 2012 19
  20. 20. IMPLEMENTATION IN MANUFACTURING Poka-yoke can be implemented at any step of a manufacturing process where something can go wrong or an error can be made. Shigeo Shingo recognized three types of poka-yoke for detecting and preventing errors in a mass production system: The contact method identifies product defects by testing the products shape, size, color, or other physical attributes. The fixed-value (or constant number) method alerts the operator if a certain number of movements are not made. The motion-step (or sequence) method determines whether the prescribed steps of the process have been followed. May 26, 2012 20
  21. 21. ADVANTAGES They are simple and cheap. 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. Once put in place, they require minimal supervision. May 26, 2012 21
  22. 22. CONCLUSION Poka-yokes deals with understanding why people make errors and how to analyze the process to know where errors are likely to occur and what root causes contribute to them. Since the poka-yoke devices detect errors at their roots n prevent them from blowing up to become bigger problems, there is consistency in the quality of the products, saving the cost and time spent in subsequent quality inspection processes.May 26, 2012 22
  23. 23. THANK YOUMay 26, 2012 23