FreeLists / si-list / [SI-LIST] Re: Off Topic Question

["Jackson, T L" <t.l.jackson@xxxxxxxx>]

In my experience,
If one has a firm description of what the design is supposed to do
and
if one is willing to put the effort into serious modeling and design checks
before starting fabrication and assembly,
one can go to production on the first layout.  This has the disadvantage of
taking the longest time until there is something tangible that Management
and/or Marketing can show to potential customers.

In the real world, someone has to make the tradeoff between the amount of
modeling performed before fabrication versus the cost of debugging and
respinning a design.  Somewhere between the two extreme of "model everything
in excruciating detail" and repeated "Build and Test" is the lowest cost,
fastest path to production.  The hard part is figuring out where this point
is for a given design, staff, toolset, company, etc.  All this assumes one
is not trying to hit a moving target, i.e. the functions, performance, cost
target, etc. are not changing during development.

Personally, I have gotten it right on the first time more than once and
never took more than two.

TJ
Thomas L. Jackson, PE
Senior Staff System Engineer
L1-50, Remote Sensing Systems Engineering
Missiles and Space Operations
Lockheed Martin Space Systems Company
telephone: (408) 742-2013
facsimile: (408) 742-7701
location: B149/E2

-----Original Message-----
From: Bill Reams [mailto:breams@xxxxxxxxxxxxxx]
Sent: Thursday, November 07, 2002 1:01 PM
To: 'Si-List' (E-mail)
Subject: [SI-LIST] Off Topic Question



Ladies and Gentlemen,

I have a question that is off topic for this list. However, as we all =
work at companies ranging from medium tech to very high tech, this =
seemed a good source for a non-scientific poll.

For your "typical" projects, how many circuit board revisions does it =
take to go from the block diagram stage to full production release?

I know that in the perfect world, everyone would answer "One board, my =
first prototype is always perfect." But we've probably all seen the =
project where we're sent off to design a left-handed widget and =
eventually deliver the flux capacitor that they really wanted - but only =
after a large number of revisions and redesigns because they couldn't =
figure out how to ask for what they wanted. What I'm interested in is =
not the extreme revision numbers, but the typical number of revisions =
for typical projects. And please do include all revisions for DFM, DFT, =
EMC/EMI related modifications.

Thanks for your responses.
Bill

_______________________________________
|                                      |
| Bill Reams  - Sr. Hardware Engineer  |
| 512-928-7201 (direct)                |
| 512-349-0300 (Main)                  |
| breams@xxxxxxxxxxxxxx (e-mail)       |
|______________________________________|

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