Poka-Yoke
ポカヨケ·poka-yoke·"mistake-proofing, error prevention"
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Poka-yoke is mistake-proofing - designing processes and devices to prevent errors or make them immediately obvious.
Definition
Poka-yoke, coined by Shigeo Shingo, means "mistake-proofing" or "error prevention." It encompasses simple devices or design features that either prevent errors from occurring or make errors immediately obvious so they can be corrected. Poka-yoke recognizes that humans will make mistakes—especially in repetitive work or under stress—and designs systems that account for human fallibility rather than relying on attention and effort alone. The most effective poka-yoke makes errors impossible by design; the next best makes errors immediately detectable.
Examples
A connector designed to fit only in the correct orientation is poka-yoke—assembly errors are impossible because incorrect assembly is physically prevented. Similarly, fixtures that won't accept parts loaded backward prevent orientation errors.
Key Points
- Prevention (error impossible) is better than detection (error visible)
- Poka-yoke should be simple, reliable, and close to the point of error
- People make mistakes; good systems account for human fallibility
- Poka-yoke often emerges from analyzing past errors
Common Misconceptions
Poka-yoke is expensive technology. Many effective poka-yoke devices are simple and inexpensive—a guide, a color code, an asymmetric design. Creativity matters more than budget.
Poka-yoke replaces training. Training teaches correct methods; poka-yoke prevents errors when correct methods aren't followed. Both are needed—poka-yoke is backup for human fallibility, not replacement for competence.