100-Metodos-de-Qualidade-Total

ANALYTICAL METHODS
89
Method 36
Evolutionary operation (EVOP)
Purpose
A sequential experimental procedure for collecting information during online
production to improve a process without disturbing output.
When to use
When off-line experimentation is expensive and you would like to use online
process control. It should be run not only to produce product but also
to provide information on how to improve the process and product.
How to use
It requires a simple two-stage process using simple statistical concepts. It
is run during normal routine production by plant personnel. At each
stage a simple design is used to estimate the direction of increase or
decrease of the yield as required by the experiment. Through the planned
introduction of minor variants into the process, the operating conditions
are made.
Proceeding a certain step-length in the required direction, lay down a
second experiment to re-estimate the increase until there is no further
improvement. Constant repetition of this programme will lead to continual
improvement of the process.
Benefits
It provides sequential searching of the design space for the improvement of
the process without disturbing production.
Example
In an industrial process, two temperatures are identified as having an effect
on the percentage of parts with no faults. The two temperatures are surface
temperature (tl) and base temperature (tz). The first experiment gave the
following results: