Poka-Yoke is error proofing that prevents mistakes, makes abnormalities obvious, or stops defects from moving to the next process.
Definition
Poka-Yoke is a Japanese term commonly translated as mistake proofing or error proofing. It refers to product, process, fixture, software, and workflow designs that prevent errors, detect abnormal conditions, or stop defects before they reach the customer.
Strong poka-yoke controls make the correct action natural or unavoidable instead of relying only on attention, memory, training, or inspection.
History
Poka-yoke is strongly associated with Shigeo Shingo and Toyota Production System quality-at-the-source practice. It helped shift quality thinking from sorting defects after production to designing processes that prevent or immediately expose errors.
When to Use
Use poka-yoke when recurring errors involve wrong part, wrong orientation, missing component, missed step, wrong setting, wrong label, data entry, sequence errors, or safety-critical actions. It is especially important for high-severity risks and repeated human-error failure modes.
Step-by-Step
- Define the mistake, defect, and customer or process effect.
- Observe the work where the mistake occurs.
- Identify the error path and trigger condition.
- Choose prevention over detection where feasible.
- Design the simplest reliable control.
- Pilot with real users and abnormal conditions.
- Verify defect reduction and usability.
- Update FMEA, control plan, standard work, and maintenance checks.
Examples
- Mechanical: A fixture accepts the part in only one orientation.
- Electrical: A connector is keyed to prevent wrong connection.
- Digital: A system rejects impossible date or quantity entries.
- Assembly: A sensor confirms all components are present before release.
Common Pitfalls
- Calling signs or reminders error proofing.
- Designing a control that operators can easily bypass.
- No maintenance plan for sensors or fixtures.
- Solving detection when prevention is practical.
- Ignoring usability and flow impacts.
- No verification after installation.