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Resin Burn out problem


#1

Dear Orchidians… I am facing some difficulties in burn out cycle
for resin. I am not getti ng clean / smooth surface. Surface finish is
very poor.

We are stepping in to CAD-CAM. We are taking Resin Pieces from Wiper
Mach ine The casting surface is very rough. Following are the
parameters of burn out process.

- Investment powder - SRS Stone Cast.
- Burn out cycle - Max 700 degree C, hold for 5 hrs.
- At the time of casting - Silver temperature - 1030 degree C.
- Flask Temperature - 560 degree C

We are having Neutec make casting machine.

Help or Hints in this regards will be highly appriciated.

With Best Regards,
Ketan J Shah.
P.D. Executive.
K.B.S. Designs.


#2

Here’s the recommended procedure from PMR for casting stones in
place

SRS STONECAST R & R SOLITARE

Recommends 2 to 3 hour set up time. Recommends 2 hour set up time.

Steam De-wax - ? to 1 hour Steam De-wax - Optional

356 deg. F - 3 hours 302 deg. F - 4 hours

428 deg. F - 3 hours 707 deg. F - 2 hours

707 deg. F - 3 hours 1247 deg. F - 3 hours

1022 deg. F - 2 hours Cast Temp. - 3 hours

1166 deg. F - 6 to 9 hours Burn out temperature can vary depending
on type

Are you mixing the correct proportions of investment to water? Are
you letting it sit long enough before putting it into the oven? Are
you using a slow enough burn out?

It may help to leave some room under the flask to allow more oxygen
to enter the flask to promote full burn out. Leaving the oven door
slightly open may help as well.

Are you using a gas oven? That might be a problem.

You may be getting ash residue. I haven’t tried casting Viper resin.
I’ll ask around if you don’t get further help with this particular.

Hope this helps
Jeffrey Everett


#3

What is a “Wiper”, a stereo-lithography machine? What sort of resin
are you trying to burn out? Some just don’t work very well. Is this
an experimental process, or did somebody tell you this would give
good results? Think about cleaning up the resin masters, pulling a
RTV mold from them, and casting wax in these molds, which will burn
out perfectly.

Andrew Werby
www.computersculpture.com


#4

One very good reason to mill wax. Granted working within the 4 axis
geometric limitions does make a 5 axis mill look very tempting at
least I don’t have the additional worry of casting problems.

Jeff


#5

The resin built in the viper machine is virtually impossible to burn
out cleanly; I have certainly tried. The best way to deal with these
is to make a urethane (not silicone) mold of the resin and use the
injected waxes from this mold to cast.