From: L Smith
Subject: Re: Design of Experiments Workshop in NYC, SF, Miami
Date: Thu, 12 Dec 2002 12:10:59 -0500
Organization: MindSpring Enterprises
X-Server-Date: 12 Dec 2002 17:07:48 GMT
X-Mailer: Mozilla 4.76 [en] (Win98; U)
John Larkin wrote:
> since you actually use DOE, what do you think of my rant, declaring
> DOE to be the natural enemy of proper first-time design? I try very
> hard to make me and my engineers do solid, quantitative hardware and
> software designs that can be put into production with a minimum of
> tweaking and debugging, and I think that optimization-by-experiment is
> not only a nasty habit to form, it actually doesn't work in real life.
I'm late to this thread since I've been without power for the last week
(part of the Carolina ice-storm you might have heard about recently).
If I have the attributions right, I believe you earlier mentioned that this
thread was being posted in an electronics group, and that you believed
anyone who didn't design his/her circuits right the first time didn't know
their subject. I'd just like to point out that the thread is also appearing in
a chemical engineering group where the situation is not as clear-cut as
you would have it seem.
In various parts of the 'chemical' industry, if you wait to build a plant
you understand the process, you might as well not bother building the plant.
This is because someone else, who is willing to accept a partial understanding
of the process, will have built their plant first and will have captured the
market. This is especially true in basic consumer goods (think Proctor & Gamble
and laundry detergents, for example). In these cases, you want to run the
fewest tests of the process you can get away with and still get some idea
of the process conditions you need to run at. You also couple this with your
understanding of basic principles to make an educated guess about optimum
conditions, but you are always aware that there may be unexpected
going on that you don't know about. You also figure there will be a chance
later to optimize the process - assuming the product is successful.
This does not mean we can't design processes from first principles. Most
chemical companies don't even bother to test 'simple' distillations in the lab
anymore, the simulations are very accurate for these systems.