On Sat, 08 Mar 2008 12:09:28 -0500, axolotl wrote:

Tim Wescott wrote:

My plan was to get budgetary pricing

That changes things a bit. You may find "budgetary pricing" is a foreign
concept to most working fab shops (the fellows here that run shops could
tell us).

You apparently are in contact with engineering students- You might want
to slide one of them a few bucks and get dimensioned/toleranced drawings
to send out - or - have it given out as a mechanical engineering
problem.

I'm a consulting systems engineer, so I'm in contact with any number of
working mechanical engineers. Some of them are willing to help out for
beer, in little bits at a time. Some of them are willing to expend
chunks of time -- but they're the consulting mechanical engineers, who
have this strange notion that they should be paid for that sort of thing
(it's a fine notion, but only when I'm getting the money :-).

All of this is complicated by the fact that most of the places where I
rub shoulders with such people are either instrumentation houses or
aerospace houses. For those sorts of places "cost effective" means that
you hog it out of 6061-T6 with 1/2 inch sections for rigidity and a nice
web of pockets for lightness, and then you don't expend any more
engineering time later messing with things falling out of spec. I would
get a design that could be used for aligning lasers, but not, perhaps,
for selling to individuals.

If you can give us more detail about what you need to do (having mounted
a fair number of servo pots I don't understand the .001" tolerance) the
folks here can give you some ideas about how to do it in budget within
the design parameters. We can't help it.

I could be totally wrong with that, which is why I'm working on opening
it up. The tolerance comes from what appears to be a 0.005" off-center
requirement from an under-specified but really cheap pot, then the
necessary stack up to get from the bearing center to the pot center with
the pot mounted on a circuit board.

See my post titled "Anyone with experience with this sensor?" for the
part I want to use. It's way cost-effective, so I can't imagine that it
would demand tens of dollars in the mechanical assembly to mate up to it,
yet I can't figure out how to make it work without holding tolerances
that tight.

I'd love to see an assembly where it's used -- that would probably clear
up a lot of confusion.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html