Poka-Yoke

1. Poka-Yoke Dhon G. Dungca

2. What is Poka-Yoke? • Poka (Poh-Kah) • Inadvertent errors • Yoke (Yoh-Kay) • To avoid • Technique for avoiding simple human errors at work • “fool-proofing” • “fail-safe” • “mistake-proofing the process”

3. Shigeo Shingo • Developed the idea into a formidable tool for achieving zero defects and eventually eliminating quality inspections.

4. Poka-Yoke EVERYWHERE! • Elevator alarms • 110V/220V plugs • Low battery indicator • Low fuel indicator • Alarm clock

5. 3.5 Diskette • Cannot be inserted unless diskette is oriented correctly. This is as far as disk can be inserted upside-down. The beveled corner of the diskette pushes a stop in the disk drive out of the way allowing the diskette to be inserted. This feature, along with the fact that the diskette is not square, prohibit incorrect orientation.

6. File Cabinets • Can fall over if too many drawers are pulled out. For some file cabinets, opening one drawer locks all the rest, reducing the chance of the file cabinet tipping.

7. Bathroom Sinks • Even bathroom sinks have a mistake-proofing device. It is the little hole near the top of the sink that helps prevent overflows.

8. Key Holder • In China, where electric power has been scarce, hotel rooms are equipped with a room key holder which turns off the power when the key is removed. This ensures no electricity flow to the room while it is vacant.

9. ATM Machines • New generation ATMs perform transactions without the card leaving your hand because of the beeping sound once your card comes out of the machine

10. Elevators • Many elevators are equipped with an electric eye to prevent doors from shutting on people. They also are equipped with sensors and alarms to prevent operation when overloaded.

11. Why Poka-Yoke? • FACT! • Workers finish their shift & don’t remember what they have done • Even highly skilled workers get tired and start committing mistakes • Workers get distracted and forget on a valve or switch

12. TIPCO Experience

13. TIPCO Experience

14. Fact! To Err is Human!

15. Kinds of Human Errors • Forgetfulness • We forget things when we are not concentrating • Misunderstanding • We make mistakes when we jump to conclusion before we are familiar with the situation

16. Kinds of Human Errors • Identification • We misjudge a situation because we view it too quickly or are too far away to see it clearly. • Made by Amateurs • We make mistakes through lack of experience

17. Kinds of Human Errors • Willful Errors • We decide that we can ignore rules under certain circumstances • Inadvertent Errors • We are absentminded and we make mistakes without knowing how they happened

18. Kinds of Human Errors • Due to Slowness • We make mistakes when our actions are slowed by delays in judgement • Lack of Standards • Errors occur when there are no suitable instructions or work standards

19. Kinds of Human Errors • Surprise Errors • Equipment runs differently than expected • Intentional Errors • We make mistakes deliberately

20. How to deal with errors • Errors happen • “Errors are inevitable. The mark of character is not refusing to recognize them, but acknowledging them and taking responsibility.” • Errors can be eliminated • People make fewer mistakes if they are supported by proper training and by a production system based on the principle that errors can always be prevented.

21. 5 Best Poka Yoke • Guide pins of different sizes • Error detection and alarms • Limit switches • Counters • Checklists

22. Poka Yoke Devices • Vibration sensors • Metal sensors • Timers • Computer-activated devices

23. Poka Yoke… Approaching ZD (zero defects)

24. Sampling vs 100% Inspection • Sampling inspection • “we maintain our quality at 99%” • 100% Inspection • “we won’t tolerate a single defect.”

25. 3 Strategies for ZD • Don’t make it! • The more products you make, the greater opportunity for defects to sit in inventory. • Make it to withstand any use! • Build safeguards into the production process to ensure that the product is robust from the user’s viewpoint • Once you’ve made it, use it right away • Go for continuous flow production

26. Inspection Techniques • Judgment Inspection • Separates defective products from good ones after processing • Informative Inspection • Uses data feedback to control the process and reduce the defect rate. • Source Inspection • Determines before the fact whether the conditions necessary for high quality production exist.

27. Prediction vs Detection • Prediction • System acts before a defect occurs • Detection • System does not allow continuation

28. Basic Poka Yoke Functions • Shutdown • Normal operations are stopped when defect is detected or predicted • Control • Prevents defective items from passing on the next process • Warning • System signals when an abnormality is about to occur or that a single defect has already occured

29. Basic Poka Yoke Functions • Shutdown • Normal operations are stopped when defect is detected or predicted • Control • Prevents defective items from passing on the next process • Warning • System signals when an abnormality is about to occur or that a single defect has already occured

30. Where “Mistake-Proofing” works well • Manual operations were worker vigilance is needed • Where mispositioning can occur • Where adjustment is required • Where SPC is difficult to apply • Where special causes can reoccur • Where external failure costs dramatically exceed internal failure

31. Detection Method • By characteristics • Weight, dimension, shape • Omitted processes • Process sequence method • Fixed values • Using counter