What Is Error Proofing?

Error Proofing


The purpose of Error Proofing is to eliminate product defects by eliminating errors that can potentially lead to poor quality reaching the customer.

Error Proofing, made famous by Shigeo Shingo, challenges western paradigms on building quality into a product.  In most engineering and manufacturing companies, a list of checks or ‘must do’  instructions are added to Standard Operating Procedures in the hope that they will stop errors from occurring.  Shingo took a different view and looked to build Error Proofing devices to detect, prevent or eliminate the potential error altogether.

Levels of Error Proofing

Error Proofing Level 1 – Detection  – Detecting that an error has occurred is good in that we know something has gone wrong and the process has stopped.  The downside is that some cost has been incurred in the scrapping or re-working of the defect.

Error Proofing Level 2 – Prevention – In this scenario, the error proofing device stops the process from making the defect. Sensor devices, trip light and profile gates used to detect poor position, wrong size or fallen items are common examples. Prevention is better than detection as it is easier to reset.

Error Proofing Level 3 – Elimination – Eliminating the chance of the error occurring is considered the best outcome as there is zero chance of the error leading to a defect.  Designing the error out of the process, therefore, is considered the pinnacle of error proofing.

Error Proofing campaigns based on quality issues can be the most engaging activity for frontline teams as it involves a combination of problem solving and innovation.


  • Improvement in Right First Time
  • Reduce cost on non-quality
  • Reduce re-work and over-processing


graphic showing the hierarchy of error proofing


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This page was written by Bob Newton in February 2018.
Due for review in 2019.

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