Methods that help operators avoid mistakes in their work caused by choosing the wrong part, leaving out a part, installing a part backwards, etc. Also called mistake-proofing, poka-yoke (error-proofing) and baka-yoke (fool-proofing).

Common examples of error-proofing include:

  • Product designs with physical shapes that make it impossible to install parts in any but the correct orientation.
  • Photocells above parts containers to prevent a product from moving to the next stage if the operator’s hands have not broken the light to obtain necessary parts.
  • A more complex parts monitoring system, again using photocells, but with additional logic to make sure the right combination of parts was selected for the specific product being assembled.