Emerald Resin Casting Issues

A lost wax capable resin tuned for 30 - 70 micron slice thickness
Brendan Milton
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Emerald Resin Casting Issues

Post#1 » Fri Jun 22, 2018 12:52 pm

Hello,
I have been printing in emerald resin for a few months now and casting has gone perfectly fine with highly complex ring with super fine detail. Recently I have been given the task to create a medical alert bracelet the model looks great printed with all the detail. After I remove the print I put it in warm water with dawn soap to get rid of the access resin then put it into the ultrasonic cleaner to ensure there is no extra resin. I then put it into the B9 curer for 10 min on each side. Everything looks great lettering and the medical alert symbol.

We are casting it in silver, we have cast in emerald resin no problem with bracelets and ring.Yet we are having an issue casting this bracelet, we have cast it 6 times with no luck it always turns out pitted and the lettering does not all show up because the metal has gotten in there and sometimes the silver wont go through the whole piece. We have the sliver at 1700 degrees and in the most recent one 1750 degrees and it was worse.

We use plasticast as our investment. This is the first time we have dealt with this issue. If anyone knows a solution please inform me.
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akgold
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Re: Emerald Resin Casting Issues

Post#2 » Sat Jun 23, 2018 4:47 pm

Casting silver at 1700 degrees????????
That's the problem

drop the can temps to about 1,000 to 1100 deg F.
I'm so far behind I think I'm First !!

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Robert Howle
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Re: Emerald Resin Casting Issues

Post#3 » Sun Jun 24, 2018 8:18 pm

Pouring or spin casting? Show your spruing too. 1750 casting temp, wow!

Robert
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Metalcaster
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Re: Emerald Resin Casting Issues

Post#4 » Mon Jun 25, 2018 8:25 pm

1750 is probably his sterling silver temp... not oven temp :-)
Using an Electric melter. The melter can be up to 50 oF off so thats not really the problem.
Flask temp for a thick piece doing Vacuum casting is around 800- 900 oF
If it's a thick piece, you want to add some vent rods so that you can vacuum the residue out of the cavity before pouring metal into the flask .
With Plasticast, use 36/100 investment ratio, let sit at room temp (around 70 oF) for 2 hours... go through your normal burnout that has worked for you in the past except, go to 1450 oF and hold there for 3 to 4 hours before dropping to casting temp. hold at casting temp for 1 hour to stabilize the temperature within the flask. This is where you would vacuum the interior of the flask, then put it back in the oven for 15 minutes.
Now cast and we can all ask the casting gods to be benevolent :-)

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Robert Howle
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Re: Emerald Resin Casting Issues

Post#5 » Mon Jun 25, 2018 10:35 pm

MOst flat objects i just mold them and shoot a wax. This does depend on geometry of the piece.

Robert
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grach13
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Re: Emerald Resin Casting Issues

Post#6 » Wed Jun 27, 2018 5:23 am

Hi, don`t want to create new topic for same question, i`l try to ask here.
When i cast emerald resin, i often get such bad surface on castings, but only on thicker parts, how do you think, it is my casting problem or a bad curing? white gold, plasticast. Never had same on wax models.
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grach13
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Re: Emerald Resin Casting Issues

Post#7 » Fri Jun 29, 2018 12:08 am

I read all posts about problems in casting, i make everything as recommended,ultrasonic cleaning with dishwasher soap, without alcohol, curing in water up to 2 hours under 100W 395-400nm very powerful LED with lens, using plasticast with boric acid, made holes under flasks for ventilation, lift them as needed, used burnout programs as described,and even higher temperatures, but still everyday i got bad castings...

The only one thing that i cannot do as described, is fast temperature lifting, my burnout furnace can lift only 10C* MAX (18F) at a minute, and now with ventilation even less... Is it critical????? please, help.

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Robert Howle
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Re: Emerald Resin Casting Issues

Post#8 » Fri Jun 29, 2018 3:38 am

Does your oven have a hole in the top to draw air in through the bottom of the oven? I don't know that u are getting cure with that lamp.

Robert Howle
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grach13
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Re: Emerald Resin Casting Issues

Post#9 » Fri Jun 29, 2018 4:52 am

Yes there is a hole. My wax castings of even very big rings are great, and only small rings casts great in resin.

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Stephen Attaway
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Re: Emerald Resin Casting Issues

Post#10 » Fri Jun 29, 2018 6:12 am

Eric Paul Marvets has done extensive research on casting resins. His paper from the 2018 Santa Fe Symposium can be found here:
http://www.santafesymposium.org/2018-sa ... hypotheses

Three key ideas:
1) Resin has residual stress that can damage plaster during burnout. This stress can be relieved by heating.
2) Uncured resin weakens plaster. Boiling in water will remove uncured resin.
3) You can only prevent the formation of ash. You cannot remove ash once it is formed. The flask must be dry before you start the burnout, and you must have O2 in the oven to prevent ash.

Stephen Attaway

grach13
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Re: Emerald Resin Casting Issues

Post#11 » Fri Jun 29, 2018 7:06 am

Very interesting post, thank you! So, i found there this: In short, ash is permanent. Once created, it cannot be removed. The only solution is to prevent ash by minimizing the time spent under pyrolysis. We must proceed from 400°F (204°C) to 800°F (427°C) as quickly as possible.
It can be my problem , i cannot lift temperature fast, i don`t have another furnace to test it, maybe someone can confirm that?

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Stephen Attaway
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Re: Emerald Resin Casting Issues

Post#12 » Sat Jun 30, 2018 7:32 am

A key to ramping fast is to make sure that flask is completely dry. A long hold at 274F or 350F is needed to insure that water is removed from the flask. I use a convection oven during this stage of the burnout. After all the water has been removed, I move the flask to a pre-heated burnout oven. Even with a fast ramp, you will still need O2 (heated air injection) to prevent pyrolysis.


https://en.wikipedia.org/wiki/Pyrolysis

Steve

grach13
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Re: Emerald Resin Casting Issues

Post#13 » Mon Jul 02, 2018 2:37 am

Have ordered yellow resin, will try it, maybe its a bit better than emerald...

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Robert Howle
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Re: Emerald Resin Casting Issues

Post#14 » Mon Jul 02, 2018 6:32 am

If u don't have proper cure, air flow and good burnout practices, printing with yellow is not going to solve your issues.

Robert Howle
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grach13
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Re: Emerald Resin Casting Issues

Post#15 » Tue Jul 10, 2018 9:45 am

How to understand this? Ramp at -2C
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Robert Howle
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Re: Emerald Resin Casting Issues

Post#16 » Tue Jul 10, 2018 5:22 pm

It's not a minus number. It want's you to ramp at 2degrees C per minute.

Robert
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rkundla
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Re: Emerald Resin Casting Issues

Post#17 » Wed Jul 11, 2018 11:13 am

Is it supposed to be a tilde?

~ versus -

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