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5.31 - Poka Yoke


The provision of effective quality assurance to prevent defective products being produced is essential if complete JIT manufacture is to be realised. In order to provide this, the emphasis on quality should be moved from inspection (i.e. stopping defective product being shipped to the customer) to prevention (i.e. ensure no defective product are manufactured).

In the drive towards zero defects, the use of Poka Yoke, or foolproof devices, at all stages of the production process is essential and needs to be considered and implemented wherever possible. This approach can considerably simplify final acceptance testing.

Three types of Poka Yoke:-

  • Contact Type - Use of shape, dimensions or other physical properties of products to detect the contact or non-contact of a particular feature.
  • Constant Numbers Type - Detects errors if a fixed number of movements have not been made (e.g. all parts have not been provided in a kit).
  • Performance Sequence Type - Detects errors if the fixed steps in a sequence have not been performed, or alternatively, prevents incorrect operations form being performed, thus eliminating any defects.

Activating Poka Yoke

  • Shut-Out Type - Prevents an incorrect action from taking place.
  • Attention Type - Brings attention to an incorrect action but does not prevent its execution.

As the shut-out type of activation halts processing even if the operator is not paying attention, it is preferable (where possible) to attention type activation where production continues if the operator does not notice the warning.

Methods of Activating Poka Yoke

Methods of Activating Poka Yoke

Input - Output Analysis for Poka Yoke

Input / output Anlaysis for Poka Yoke

Further Reading