Mistake-Proofing (Poka-yoke)

1. MISTAKE-PROOFING (POKA-YOKE) The Effective Approach to Zero Defects

2. NOTE: This is a PARTIAL PREVIEW. To download the complete presentation, please visit: https://www.oeconsulting.com.sg LEARNING OBJECTIVES Gain knowledge on the key concepts and principles of Zero Quality Control Learn the approaches, methods and tools for designing and implementing poka- yoke systems Identify the limitations and best practices of mistake-proofing 2 © Operational Excellence Consulting

3. CONTENTS 02 03 04 05 01 INTRODUCTION TO ZERO QUALITY CONTROL BASIC ELEMENTS OF THE ZQC SYSTEM USING POKA-YOKE SYSTEMS LIMITATIONS & BEST PRACTICES EXAMPLES OF POKA-YOKE APPLICATIONS 3 © Operational Excellence Consulting

4. TRADITIONAL INSPECTION IS A POOR SUBSTITUTE FOR QUALITY Traditional 100% inspection does not provide 100% defect-free products. 4 © Operational Excellence Consulting

5. WHAT IS ZERO QUALITY CONTROL (ZQC)? The Goal is Zero Defect Defects Can Be Prevented Does Not Place Blame on People Zero Quality Control (ZQC) is an approach for achieving zero defects. “Zero” refers to the goal of making products with zero defects. ZQC is based on the principle that defects are prevented by controlling the performance of a process so that it cannot produce defects – even when a mistake is made by a person or machine. ZQC is an approach that does not point fingers at people. It recognizes that machines and people make mistakes sometimes, and it finds ways to keep those errors from turning into defects. 5 © Operational Excellence Consulting

6. WHY FOCUS ON ZERO DEFECTS? Maintain customer satisfaction and loyalty High cost of poor quality (e.g. rework, scrap, warranty claims) Improve company image and reputation Develop a culture of continuous improvement and innovation Facilitate lean production methods with smaller inventories Improve productivity and competitiveness 6 © Operational Excellence Consulting

7. WHAT CAUSES DEFECTS? Most defects happen in one of five situations: Specification of inappropriate procedures or standards Excessive variability in the operations Damaged or excessively variable materials Worn machine parts Simple human mistakes 7 © Operational Excellence Consulting

8. THE TRADITIONAL QUALITY IMPROVEMENT CYCLE The traditional quality improvement cycle is “Plan, Do, Check” ● PLAN This cycle catches and corrects defects after they occur, but it cannot make sure that work is done according to plan in the first place An error is not the same as a defect ● ● § Catch defects after they occur An error is what happens to cause the defect ● CHECK DO § Take improvement action Rather than detecting defects, the trick is to catch the error before it turns into a defect ● 8 © Operational Excellence Consulting

9. THE ZQC APPROACH CONSISTS OF FOUR BASIC ELEMENTS Mistake-proofing (poka-yoke) systems Source inspection FOUR ELEMENTS OF ZQC A short Feedback loop 100 percent inspection 9 © Operational Excellence Consulting

10. SOURCE INSPECTION Source inspection is the key to the ZQC control function ● Source inspection assures that the conditions are in place beforehand to perform a process properly ● Source inspection is different from other types of inspection, such as judgement inspection or informative inspection ● 10 © Operational Excellence Consulting © Operational Excellence Consulting. All rights reserved.

11. THREE APPROACHES TO PRODUCT INSPECTION AND THEIR RESULTS Reduces defects by informing the process after they happen Source Inspection 1. Judgment inspection: Inspection that discovers defects Discovers defects but does not reduce them Eliminates defects by catching and fixing their causes 2. Informative inspection: Inspection that reduces defects Informative Inspection Judgment Inspection 3. Source inspection: Inspection that eliminates defects 11 © Operational Excellence Consulting

12. STATISTICAL QUALITY CONTROL (SQC) Statistical quality control (SQC) approach to inspection is to check samples of the product after processing to determine whether they are acceptable SQC is better than mere judgment inspection because it gives information back to the process ● ● However, since SQC relies on samples rather than checking every unit, it does not ensure that 100% of the products are good ● When a sample shows a problem, information is fed back to the process so that the problem can be corrected ● Feedback and corrective action are often slow ● Uses a control chart to track the results over time ● 12 © Operational Excellence Consulting

13. SOURCE INSPECTIONS PREVENT DEFECTS Discovery of mistakes before processing Source inspection is different from judgment inspection and informative inspection ● Feedback and corrective action Source inspection catches errors – and gives feedback about them – before processing ● A Process with Zero Defects This is the integration of the Check and Do stages: something controls the doing so that it cannot be done wrong ● 13 © Operational Excellence Consulting

14. SOURCE INSPECTION KEEPS ERRORS FROM TURNING INTO DEFECTS The integration of Check and Do stages keeps defects from being passed down the line. 14 © Operational Excellence Consulting

15. 100 PERCENT INSPECTION CATCHES ALL ERRORS The second unique element of the ZQC system is that it does a source inspection on every single product ● An SQC system, however, only inspects a sampling of the product and does not prevent defects from occurring ● ZQC uses methods that check 100% of the products ● 15 © Operational Excellence Consulting © Operational Excellence Consulting. All rights reserved.

16. “ Humans are animals that make mistakes.” SHIGEO SHINGO 16 © Operational Excellence Consulting

17. WHAT IS POKA-YOKE? POKA YOKE Mistakes Prevention Poka-yoke means implementing simple low-cost devices that either detect abnormal situations before they occur, or once they occur, stop the line to prevent defects. 17 Source: Based on Pascal Dennis, 2015 © Operational Excellence Consulting

18. POKA-YOKE IS WORTH PURSUING ONLY WHEN HUMAN ERROR IS THE MAIN CAUSE OF QUALITY DEFECTS Poka-yoke should not be implemented for the sake of trying to look Lean! 18 © Operational Excellence Consulting

19. TWO APPROACHES TO POKA-YOKE CONTROL SYSTEM WARNING SYSTEM ● ● Controls the process so that when a defect occurs, the process stops until correction takes place Signals operators when a defect occurs so that operators take corrective action ● ● High capability of achieving zero defects Sometimes an automatic shutdown is not an option ● ● For example, an ATM machine withholds your cash until you have removed your card so that you cannot forget the card For example, when word-processing software highlights a misspelled word so that you can go back and fix it 19 © Operational Excellence Consulting

20. THE DUAL FOCUS OF POKA-YOKE SYSTEMS –MISTAKE PREVENTION & MISTAKE DETECTION PREVENTION Poka-yoke that focuses here works on mistake prevention or making mistakes impossible. People and machines do make mistakes or errors ● A portion of mistakes turn into defects ● Process Mistakes Defects Poka-yoke systems can be applied to prevent mistakes from happening, as well as detect mistakes after they have happened ● DETECTION Poka-yoke that focuses here works on mistake detection, or making sure mistakes do not turn into defects. 20 © Operational Excellence Consulting

21. POKA-YOKE MUST BE DESIGNED TO DETECT DEVIATIONS IN THE 3M’S ? MISSING Action is not taken or part is not there. MALFORMED Action is incorrect or part is there but of wrong size, shape, color, temperature, etc. MISPLACED Action or part is there, but in the wrong place or position. Deviations in the 3M’s can be detected by contact methods, fixed-value methods or motion-step methods. 21 © Operational Excellence Consulting

22. SAFETY COVER An example of a positive stop based on the contact method is on equipment that requires operators to perform a safety task before starting the machinery. To activate the power to the equipment, the operator must first close the cover. Other examples include blenders, washers and microwaves that stop when their door is opened to prevent operator injury or damage to the equipment. ● 22 © Operational Excellence Consulting

23. PICK-TO-LIGHT A common poka-yoke system in assembly processes is light-guided picking, also known as pick-to-light. Pick- to-light devices use colored LEDs to visually guide assemblers to pick the correct parts, in the right quantities, and in the proper sequence. This motion- step method reduces the risk of human errors and speeds up build times to ensure high quality while maximizing productivity. ● 23 © Operational Excellence Consulting

24. RHYTHMIC MOVEMENT One application of poka-yoke devices is the way it supports the rhythmic movement of the operator when performing standard operating procedures at takt time. Based on the motion-step method, any deviation in the movement or results of the operator’s “dancing hands” will be detected. They cannot forget if they have forgotten anything. ● 24 © Operational Excellence Consulting

25. TIME SEPARATION Mistakes can be prevented by separating contradictory or opposing feature requirements in time. The light indicates the allowed flow of traffic separating the flow by specific periods of time. Based on the motion-step method, many stoplights are timed with a three- second delay to allow previous cars to exit the intersection before cross traffic is permitted to enter. ● 25 © Operational Excellence Consulting

26. TOOL BOARD/DRAWER Missing tools and tools lying around the workplace are challenges faced by maintenance and engineering staff. With a tool board/drawer, available tools can be easily accessed and tools after being used can be returned to their designated locations. As a visual display, any tool which is missing, in the wrong slot or being used can be easily noticed. ● 26 © Operational Excellence Consulting

27. DRIVE TENSION GUIDES Drive tension guides help operators inspect for proper tension on the drive system. Using red and green color blocks, these visuals indicate when a chain or belt needs to be tightened or replaced so as to prevent equipment breakdown. ● 27 Source: Based on Brady Worldwide Inc. © Operational Excellence Consulting

28. THREE RULES OF POKA-YOKE 1 3 3 Don’t wait for the perfect poka-yoke. Do it now! If your poka-yoke idea has better than 50% chance to succeed… do it! Do it now... improve later! 28 © Operational Excellence Consulting

29. BEST PRACTICES Poka-yoke is a means to achieve the goal of zero defects, not the end in itself Involve team members in the design and implementation of poka-yoke systems ● ● Do not react to human errors by blaming them for being sloppy Provide knowledge such as used cases to the team members in implementing poke-yoke ● ● Line process capability issues should be addressed first before implementing poka-yoke ● Do not make poka-yoke devices extremely sophisticated and complicated – go for the simplest and most effective method! ● Poka-yoke should make the job of the operator easier, not add more work ● 29 © Operational Excellence Consulting

30. END OF PARTIAL PREVIEW Operational Excellence Consulting is a management training and consulting firm that assists organizations in improving business performance and effectiveness. Based in Singapore, the firm’s mission is to create business value for organizations through innovative design and operational excellence management training and consulting solutions. For more information, please visit www.oeconsulting.com.sg © Operational Excellence Consulting