Re: Resend of Burnout Query

From: Michael C Maguire (
Date: Tue Feb 27 1996 - 18:56:53 EET


What are you burning it out from: a solid flask mold or a shell mold? If it's a
shell mold, you're likely going have a big problem. Solid patterns thicker than
about 2 to 3 mm are extremely difficult to burn out without severe cracking of
shell molds.

If it's a solid flask mold, it may be problematic depending on the geometry. If
it's smoothly radiused and the ceramic isn't required to penetrate deep, thin
pockets then I'd give it a 50/50 chance of surviving.

As to maximum temperature, I suspect your mold material may limit the time and
temperature you can tolerate. Burning out solid pieces of epoxy resins takes
much longer than the quasi-hollow patterns, so the standard 3D Systems burn-out
(1600F-20min, then 20 min to 2100F, hold at 2100 for 10 minutes, then 20 min
back to 1600F, and hold at 1600 for 20 minutes) isn't sufficient to combust
solid patterns. I'd try to leave it at 2100F, with as much excess oxygen your
gas furnace can operate at for as long as you think your shell can take it (the
time at 2100 won't kill you, but if you have a high silica shell, the cool down
cycle if done too quickly will severely crack the shell). Of course, leaving
several vent holes in the shell to assist with air cirulation during burnout is
a must, in addition to allowing you to blow the ash out when you're done.

My best recommendation would be to re-build it as a QuickCast pattern, but if
you have several thin sections that are oriented differently, then draining the
pattern may not be so easy anyway. If you have an .stl file available on an ftp
server, I'd be willing to take a look at it and make some more concrete

Mike Maguire
Senior Member of the Technical Staff
Sandia National Laboratories
Albuquerque, NM

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