Issues With Surface Roughness Castable and Castable Wax

What could be causing this surface roughness on my castings? I’m currently using the new castable wax resin from formlabs, but it also happened with their regular castable resin. I’m using their recommended burnout schedule and r&r plasticast investment. Any tips or advice would be really appreciated. I’m pulling my hair out over here.

I’ve had the same problem, I have used several burnout cycles, different investments, different casting temps, not a bit of difference. Still looks like it was dipped in sand before casting! Has anyone tried curing this purple castable? Has anyone gotten super results?

I have been having the same problems. I would love to know who, how, if??? the castings in the promotion for the new resin were cast. i think they might be renders at this point.
I was using the old blue castable and i finally got some really good results. it took about 50 castings to dial it in. The problem i had with the old castable was the viscosity. it would print small details in negative, like lettering inside a ring, but the resin would pool in the detail and harden there so the detail was washed out. When this new resin came out i jumped on it hoping that since it did not need curing it may clean out better. I got about 10% better printing with it, but the surface of the castings is terrible. I see many other people posting the same results. Even the photos they post look just like mine.
I am going back to the blue and curing it for hours. That worked for me. I did find that the burnout schedule they recommend is too fast in the beginning. I am starting with a 100 degree kiln instead of a 150 ©. then i am extending the ramp to 371 to 200 minutes. This is because the thermal expansion of the plaster and the resin is higher per degree at lower temperatures. IE, from 1 degrees to 2 degrees is a 100% increase in temperature. From 100 Degrees to 101 degrees is a 1% increase, therefore the thermal expansion is incredibly more at the low end of the cycle. Putting a flask in a kiln at 150 c is really causing a lot of thermal expansion and the wad, or resin is still hard so the expanding plaster is forced into a pressure against a hard resin surface. i want to get the resin softened as much as possible before the plaster expands too much. that calls for a slower ramp up from room temperature to 150 c. I will try it and let you know.
best
Greg Neeley

Hi all, I was having the same problem. The issue is letting oxygen feed into the kiln. With large industrial type factories, they use gas kilns with sophisticated air feeding systems, thats why they get such great results. These modern 3D resins need tons or airflow to completely combust and leave no residue. For anyone who has a small micro foundry, we are using electric kilns and they have no real internal airflow.

At first I tried side venting my electric kiln by drilling holes in the door of my kiln. That will not work as it has to be vertical air flow not horizontal are flow. Recently I retrofit my kiln with a industrial type fish tank pump and stainless steel brake line. (I have heard some people drill holes in the bottom, but I preferred to add airflow with a fish tank pump)

If you see the photos below you’ll see how I didi it.

IMG_2386

IMG_2387IMG_2392IMG_2396

I use an extended burn out cycle. 300degrees 2 hours, 700 degrees 2 hours, 1450 degrees 6 hours, 960 2 hours - I cast at 960 after 1 hour of soaking at that temperature. This is important as you need the investment to fully harden before the true burnout happens.

Another important thing to do is vacuum out the bottom of the flask with a shop vac just before casting. Also it is important to use vents on the flask with Wax Web or use perforated flasks. Because the resin is a combustable material, you need the gases to vent through the investment.

Hope this helps!
Best
TM

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I forgot to mention after all these steps I get flawless perfect castings with the new castable resin.

Good luck!

Best
TM

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PS - I used a layer of DUROCK (home depot 10 bucks) between the stainless steel tubing and the kiln wiring. Concrete fireproof sheet to insure against melting the kiln wiring, don’t think I really needed it but added it just for safety. You’ll see it in the above photos.

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