Poka Yoke

Poka Yoke, also known as error proofing, is a systematic process for the review and reduction of the source of errors in a process.

Errors are the source of defects, so eliminating errors will eliminate the associated defects.

Shigeo Shingo introduced the concept of Poka Yoke at Toyota Motor Corporation in 1961. Originally known as baka-yoke (which means fool proofing), the name was altered to Poka Yoke to prevent offence and is pronounced  POH-kah YOH-kay'.

Shingo said "Defects arise because errors are made. Errors will not turn into defects if feedback and action takes place at the error stage"

When To Consider Poka Yoke

The best time to consider error proofing is at the process design stage, Process FMEA facilitates this as part of the 'Control' considerations.

However, in a number of cases, error proofing (Poka Yoke) is used as an integral part of continuous improvement (Lean and 6σ) and problem solving activities.

Common Causes Of Error

• Machining the wrong part
• Operation error (wrong specification used)
• Adjustment, measurement or dimension error
• Errors caused by badly maintained equipment
• Errors caused by incorrect or unsuitable equipment
• Process ommissions
• Process errors (not following standard procedure (SOPs))
• Set up errors
• Missing parts
• Incorrect part used
• Wrong form used
• Incorrect details entered

It would be easy to blame 'people' but in fact the root cause of the error is the process or SOP itself. This needs to be fixed at root cause level, and this is where Poka Yoke  is used.

The Process

There are a few steps to be considered and these are:

• Define the error (the root cause of the defect)
• Establish Poka Yoke device or process
• Test the Poka Yoke device, validate and evaluate (cost, effectiveness, complexity)
• Plan and implement the Poka Yoke device
• Verify improvement
• Sustain the improvement (make it the new way)
• Replicate - use the lessons learnt

Update All Records

Ensure that all documentation is updated, which should include:

• Control Plans
• Reaction Plans
• Process FMEAs

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