Pokayoke / Error Proofing

Why do we need error proofing ?


Error proofing enforces operational procedures or sequences, ensures quality at the source instead of quality after the fact and eliminates choices leading to incorrect actions.

  • Use error proofing devices & techniques to achieve zero defects and eventually eliminate wasteful quality inspection procedures.
  • Respect the intelligence of workers by taking over repetitive tasks or actions that depend on vigilance and memory.
  • Error proofing can free a worker’s time and mind in order to focus on their true skills and more value added activities.
  • Individually errors are rare. However, as a group they are a major cause of failures
  • Parts and processes can be controlled in ways that  dramatically reduce the occurrence of failures due to mistakes.
  • Mistakes and errors always occur, we need to ensure that they do not cause customer defects.

 We need to understand the difference between errors and defects :

  • An error is any deviation from an intended process.
    • Errors occur when any condition necessary for successful processing is improper or absent
    • All defects are created by errors
    • Not all errors result in defects
  • To be a defect:
    • The product must have deviated from specifications
    • The product does not meet customer expectations

“Be more careful” not effective :

  • “The old way of dealing with human error was to scold people, retrain them, and tell them to be more careful … My view is that you can’t do much to change human nature, and people are going to make mistakes.  If you can’t tolerate them ... you should remove the opportunities for error.”
  • “Training and motivation work best when the physical part of the system is well-designed.  If you train people to use poorly designed systems, they’ll be OK for awhile.  Eventually, they’ll go back to what they’re used to or what’s easy, instead of what’s safe.”
  • You’re not going to become world class through just training, you have to improve the system so that the easy way to do a job is also the safe, right way. The potential for human error can be dramatically reduced.”