Poka Yoke

Poka-Yoke (Fail Safe)

(Source – Make your service fail safe by Richard B Chase & Douglas M Stewart)

Def –

· Fail safe methods to prevent human errors from becoming defects in the end process

· Fail safe method strives to make the product / process resistant to factors within its control & then strives to extend the scope of the control to outside factors

· They are

ü Warnings – Signals existence of a problem. Only indicates that mistake has been made.

ü Controls – That stop production until the problem is resolved. It forces the operator to correct the mistake before proceeding.

· Example – Limit Switch indicates improper alignment of parts on machine.

ü Warning – Light connected to the switch will glow and shows mis-alignment

ü Control – Machine shuts down till the alignment is corrected

Where 100% inspection can be performed (Shingo’s Method)

1. Successive checks – Person in the next stage supplies information about product error & hence, stops the production line.

2. Self Inspection – Operator inspects his / her own work

3. Source Inspection – Operator inspects all the mistakes which have not yet resulted in an error in final product

All the above shortens the feedback loop between mistake error, its detection & subsequent correction.