# Poka-yoke

Operations · `Poka-yoke` · verification: source checked

Poka-yoke is a Japanese term for error-proofing. It uses devices and design features to help operators avoid mistakes such as using the wrong part, leaving out a part, or installing a part backwards. The purpose is to find defects at their source and work toward 100% quality.

## Specification

| Property | Value |
|---|---|
| Kind | methodology |
| Origin | Japanese term |

## Safety

- Blind spot warning in a vehicle is given as an everyday example to prevent accidents.
- Auto-stop on a table saw is given as an everyday example to prevent injury.
- Auto-brake in vehicles is given as an everyday example to prevent collisions.
- Washing machines will not start until the door is closed and will stop if opened mid-cycle.
- Lawn mowers operate only when a safety bar is held down and switch off when released.

## Study notes

- Poka means inadvertent error; yoke means prevention.
- The purpose of poka-yoke is to achieve 100% quality by finding defects at their source.
- The document contrasts poka-yoke with quality by sampling inspection and quality by 100% inspection.
- The two types of poka-yoke are shutdown and warning.
- Shutdown poka-yoke can prevent a machine from starting if a workpiece is set incorrectly.
- Warning poka-yoke alerts to abnormal conditions by buzzer or light.
- Criteria for good poka-yoke include simplicity, long life, low maintenance, high reliability, low cost, and design for the workplace situation.
- Examples include product designs with physical shapes that make incorrect orientation impossible.
- Examples include photocells above parts containers to prevent a product from moving to the next stage until the operator's hands break the light to obtain parts.
- Examples include a parts monitoring system using photocells with additional logic to confirm the right combination of parts for the product being assembled.

## Sources

1. [Poka Yoke - A Resource Guide | Lean Enterprise Institute](https://www.lean.org/lexicon-terms/poka-yoke/) (accessed 2026-10-25)

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