Learn the principles of mistake-proofing, distinguish prevention from detection and warning, explore practical manufacturing and service examples, evaluate solution concepts, and create a structured Poka-Yoke project with portable JSON save/load and a professional printable report.
A mistake is an unintended action or omission. A defect is the nonconforming output produced when the process permits that mistake to continue.
Training, signs and attention are useful, but they are weaker than a physical, electronic or logical control that makes the wrong action impossible.
Where the error cannot be eliminated, detection should occur at source before value is added, the condition becomes hidden or the product leaves the station.
| Level | Purpose | Typical mechanism | Example | Relative strength |
|---|---|---|---|---|
| Eliminate | Remove the error opportunity or unnecessary task. | Process redesign, part simplification, automatic completion. | Use one common fastener instead of two easily confused types. | Strongest |
| Prevent | Make the incorrect action physically or logically impossible. | Keying, locating pins, interlocks, software rules. | A fixture accepts the component only in the correct orientation. | Very strong |
| Detect and stop | Identify the error at source and stop progression. | Sensors, counters, barcode checks, vision, torque monitoring. | The cycle cannot close until all six fasteners are confirmed. | Strong |
| Warn | Alert a person and rely on a response. | Lights, alarms, labels, prompts and checklists. | An alarm sounds when the wrong programme is selected. | Weakest |
Checks a physical characteristic such as shape, size, colour, position or presence.
Checks that a specified number of actions, parts or operations has been completed.
Checks that required actions occur in the approved sequence.
Risk: wrong fastener type or missed installation.
Poka-Yoke: kitted fasteners, barcode verification, tool recipe control, fastener count and station lock until completion.
Verification: challenge with wrong part, duplicate scan, missed cycle and tool disconnect.
Risk: incorrect heat-treatment, plating or cure programme.
Poka-Yoke: scan part and route card; PLC loads only the approved locked recipe; unauthorised recipes are unavailable.
Verification: challenge with an incompatible part number and expired approval.
Risk: wrong ratio or omitted activator.
Poka-Yoke: keyed dispensing connections, gravimetric recipe control and container release only when the required ratio is achieved.
Verification: simulate underweight and overweight additions.
Risk: missing coverage, expired certification or incomplete records.
Poka-Yoke: mandatory technique selection, personnel authorisation check, coverage checklist and blocked report approval until required evidence is attached.
Verification: attempt approval with missing zones and expired certification.
Risk: component fitted 180 degrees out.
Poka-Yoke: asymmetric feature, unequal locating pins or fixture nest matching only the correct orientation.
Verification: attempt incorrect loading using representative variation and worn fixtures.
Risk: invalid serial number, wrong revision or missed approval.
Poka-Yoke: controlled dropdowns, format validation, cross-record checks, mandatory approvals and role-based permissions.
Verification: invalid formats, duplicate serials, obsolete revisions and unauthorised users.
| Concept | Control level | Risk reduction | Reliability | Ease of use | Low cost | Low complexity | Total |
|---|