On 04/09/2011 10:52 AM, jim wrote:
(top posting fixed)
Tim Wescott wrote:

On Sat, 09 Apr 2011 00:32:29 -0400, Ed Huntress wrote:

"Tim wrote in message
...
On Fri, 08 Apr 2011 23:16:17 -0400, Spehro Pefhany wrote:

On Fri, 08 Apr 2011 23:08:55 -0400, Spehro Pefhany
wrote:

On Fri, 08 Apr 2011 21:38:25 -0500, the renowned Tim Wescott
wrote:

I want to make a bunch of identical molds, for 3/4" diameter model
airplane wheels.

snip
Why not just get or make a master pattern and then make an epoxy mold
from that?

-jim


Because the process is to put a flat piece of foam in the mold, clamp
it, then chuck it in an oven to heat. The foam* softens and expands to
meet the edges of the mold. Then you take it out of the oven and let it
cool, and voile! A part (or a mess -- it's best to enter any sort of
casting process with your eyes open).

So I like the idea of using something that's nicely heat conductive. I
could look around for a heat conductive epoxy (JB Weld may work, even --
I understand that it's metal filled). But it's hard to beat aluminum
for heat conductivity and easy machining (well, brass maybe). And it
looks purty.

I'm inventing the process, at least as applies to 3-D molding. I may be
the 90000th person to do this, but _I_ haven't heard of anyone doing
this. I've heard of folks molding Depron sheets around forms, by
binding the sheet to the form with Ace bandages, then heating. It's
what inspired me to try this -- but this is something that I'm cooking
up** out of my own head as I go.

* The foam is Depron, which is a close-cell polystyrene foam sold as
insulation in Europe, but used for model airplanes the world over.

** Pun not intended, but welcomed with open arms.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html