100-Metodos-de-Qualidade-Total

MANAGEMENT METHODS
43
Method 12
Error proofing (pokayoke)
Purpose
To design an operation in such a way that specific errors are prevented
from causing major problems to the customer.
When to use
It can be used when defects occur and require 100 per cent inspection,
immediate feedback and action at the:
• source of raw materials and components
• start of the production process
• production points where an error may occur
How to use
In a pokayoke system, carry out automatic continuous inspection and, if
abnormalities occur, then provide feedback and take action. However,
before processing can begin, one has to halt the process, obtain feedback
and execute necessary action.
Benefits
Unlike statistical quality control systems, in which a fairly long time elapses
between the 'check' stage and the execution of feedback and action,
pokayoke minimizes defects by carrying out feedback and action immediately
at a low cost.
Examples
A large steel press is automatically monitored for wear. If the thickness
becomes less than a specified amount, an alarm sounds and action has to be
taken to rectify the error.
A second example involves a car manufacturer which was concerned to
prevent omission of car door pockets in production . The operation in
which pockets were mounted on the door trim involved three specifications,
and workers occasionally neglected to mount the pockets, or
mounted them incorrectly, according to their attention to work in progress.
To improve the process, door trims were exposed to a detector which
recognized whether pockets were missing. If right and left pockets had
been reversed or if a pocket had not been mounted, a buzzer sounded, air
stopped flowing to the screw-tightening lock and the operation could not
proceed. In this way, instances of pocket omission were eliminated.