Purple resin castable


Hello @Topramen20! Maybe you can help me out. I bought Castable Wax resin and got great results on the first 2 prints. But after that the results have been really bad. Have you or anybody using this resin (I’ve read some people had bad results) has had this results?
The top is in really bad shape and the bottom looks really good. I don’t understand why. Any Ideas?


Can you give me specifics on your burnout process? What temp sequence do you run and how long do you hold at each sequence. What type of investment are you using and how long do you let the investment sit out before putting it into the oven? What is your final casting temp of the flask?

Also, on a side note. I would suggest putting an auxiliary sprue starting from the base of the ring going to the center, below the head. That will insure that your molten metal will properly fill the empty cavity, allowing the piece to cool evenly ( less porosity and a much higher chance of a perfect casting).


Thank you very much @Topramen20 for helping me out.
I am using the burnout process formlabs recommends.

Ramp Full 300F
Hold 60min / 1:00h 300F
Ramp 100min / 1:40h 700F (240F x h)
Hold 120min / 2:00h 700F
Ramp 180min / 3:00h 1350F (220F x h)
Hold 280min / 4:40h 1350F
Ramp 100min / 1:40h 900F (-240F x h)
Hold 180min / 3:00h 900F

We are using R&R Plasticast with bandust and we are letting it dry from 2 to 3 hours.
We are casting at 900F with a classic vacuum casting machine.

I will add a sprue on our next cast so we can compare the results. I don’t really get what went wrong since the first cast with the purple resin worked fine. Sure thing we are doing something different.

Any thoughts on what we could be doing wrong?


This process is delicate, so any sort of mistake could snowball into a ruined casting. To me, it seems like everything you are doing is perfectly fine. Only difference is I leave my flasks out for around 7 hours now before burn-out overnight. Also, I use a Neycraft centrifugal rather a vacuum cast.

I would just go through each part again and double check things such as if the investment is still good ( this helped solve our issue as our investment went bad and was clumping, brand new investment helped), how long and how well you mix the investment/vacuum it, how the actual piece is designed (this one is particularly important as some pieces are just destined to fail if its not sprued up correctly), and so on.

Just to clarify why this process is delicate, when I was milling out and using wax, this process was much more forgiving. I never had issues with burning out wax. Resin was a much different story, I had to fine tune each part of our process, once I found a rhythm that worked, I follow it to the T. I suggest adding an auxiliary sprue and seeing what the outcome is.


Thank you @Topramen20! I guess it will be a bit of trial an error to find our sweet spot in every part of the process. We changed to R&R about a month ago, so I don’t think this will be the problem. I might hold the oven at 1350 for one more hour to see the results.
You are so right. The wax is so much forgiving. We casted wax and resin and the wax came out 100% but the resin didn’t.
I will recheck every part of the process! Thank you very much


We experienced variations in casting quality as well.
We send our printed parts away to a casting company. They use their standard investment and burnout-schedule.
The first two batches had a poor quality: Rough surface, many cavities.
Our third batch however had a perfect quality: Smooth surface, no cavities. I could even see the CATIA tessellation surfaces in the casted part. According to the casting company the burnout schedule und the investment was identical. It was MUCH better than the blue V1 or V2.
For far we determined two factors that seem to have a great impact on print quality:
• Avoid sharp edged on small details: Even a tiny corner radius (0,1mm - 0,2mm) helps!
• Make sure your parts are REALLY clean: It’s best to use fresh IPA for the final rinse. We put our printed parts in a thin-walled plastic drinking cup filled with fresh IPA and put that cup in an ultrasonic cleaner. Dry the parts with compressed air.
Of course, this is more like a good educated guess!


Thank you @Mancke! That idea of cleaning the pieces in the plastic cup in an ultrasonic sounds great!
My guess is that the problem is a result of the fact we are just letting the investment cure for just 2 or 3 hours. Will give it a try tomorrow and let you all know how it went.


Hello… i wonder if the purple castable wax resin need to be cure???


It does not NEED to be cured, however you can. It may cause slight shrinkage if cured, but again it is not required with Castable Wax.


I wrote a new topic yesterday with the same question, which is pending. To a degree, I don’t buy it. I’ll say we’ve had our machine only a week, but we’ve been casting resin for some years. Last weekend cast a fairly rigid test - all simple band rings with some channel setting. One silver cured in a nail UV box, one silver dipped in React-shun, and a 14kY cast straight off the print. Silver was good to better, gold was junk. Very careful - one batch of investment, one burnout, all the same. Torch cast with oxy-acetyline and 45 years practice. Something is up here.


We want you to succeed with our products so that you’ll keep buying them. It doesn’t do us any good to withhold information about how to get good results. I hope our support gets back to you with the latest information!

With all due respect to your experience (I wish I had 45 years of practice casting!), I think you’re describing an experiment with enough variables to make it difficult to draw a conclusion. Even if all three rings were identical parts, you say you did three different things with the three prints prior to investment, and then you cast with two different metals. Unfortunately, I’m ignorant as to whether you can usually expect two matching investments on the same burnout schedule to cast equally well with a sterling silver and a 14kt gold alloy. Is it safe to assume you’re using gypsum/plaster investment in steel flasks here, and torch cast means you’re melting your metal in a crucible that centrifugally flings the metal into the flasks, or you using a different system, like blocks or shells or phosphate binders?

Also, unfortunately, burning out thermoset photopolymer resin is very different than melting/burning out thermoplastic wax, even when following a recommend temperature ramp/hold schedule for the burnout. So if the parts weren’t identical, that could have an effect, or if you added any wax spruing differently between the parts when you invested them, that could have an effect.

Because you have to burn away the mass of resin rather than melt out wax and burn the residue, air (oxygen) flow into your investment can become an issue, so three identical investments of identical parts with no extra wax could still burn out differently if one of them’s in a spot in the kiln/furnace with the best air flow and the other two are in more stagnant air.

As for post-curing, it shouldn’t make much of a difference, but it shouldn’t hurt either if you want to post-cure because you believe it will help, or if you’ve done controlled tests that show it works better for you. The thermal part of a post-cure step could help dry off any IPA or solvent from the washing process but that should happen just as well during the burnout. Exposing a Purple Castable Wax part to more UV light might change the mechanical properties a little bit by causing some additional polymerization in the part, but that shouldn’t have much effect on how it’s burnt out and oxidized to gases inside the investment.


I have 2 theories for now why some casts come out perfect and others are scrap. I must say that i’m not a caster or goldsmith but a 3D printing company owner so my conclusions are not from the guild :wink:

  1. Wall thickness! Big parts tend to crack or at least erode the plaster investment during the burnout. My colleagues are still trying to finde what’s wrong, but simply puted: you’ll most probably fail if you cast ring with both thin details and big walls at other places. This can be somewhat managed by hollowing the more rigid parts but… This will trap uncured resin (if there’re no holls) and/or alcohol from the washing if there’re tubes due to the small openings.
  2. Support tip points are differently cured! I may be wrong but the small points where the supports meet the ring (you can see the pic of a ring we made with customer file I’ll upload at the end) are differently cured then the rest of the model. I noticed that when printing relevantly thin walls with supp tip of 1mm (or max touch point size) and 0.5mm or less thin wall with white resin. You can run this test yourself and see that after removal you can easily see the over cured spot if you point some light thru the wall. My guess is that the same effect toke place with the Purp. resin and lead to difference in the burnout phase… The following pictures shows how good the is the face where we didn’t have supports compared to the side with supports. Notice that the model is impossible to print without a lot of supports.
  3. Just to repeat how important the airflow is! You just need it if you wish to have even a moderate success!
    I hope this will help you to improve your results!


Thanks to all - I opened a new topic the other day but this topic is the same and it’s good to be public. And thanks to Ike for the reply but my quote from it is enough.

We are (as I said) a pro fine jewelry manufacturer. We don’t cast thousands of ounces but we cast 2-3 times a week for decades now. Gold of all kinds and silver. Next door is the same but they have Solidscape AND Formlabs 2. Across the hall they have 4-5 machines, one being Formlabs. Next door to them is another casting shop who has been running tests on these castable resins from ANOTHER machine upstairs. We have been casting 3D printing since it was possible to cast them - at least 15 years. Back then the growth lines were big enough to park your car in.

Let me clear here: I can’t put a percentage on it, but it’s easier to say that we have 100% success with casting wax, except once in a great while (maybe a decade) there will be a problem. We generally stop spruing problems before they start. What this means to us is English. When Formlabs says their resin is castable we expect to be able to cast it, plain and simple. And if it needs special treatment, we understand that, just tell us what it is. And no, the investment doesn’t care if it is gold or silver.

The picture by the OP, and my picture here of the gold, is classic and typical degradation of the boundary layer where the investment has broken down due to infusion/contamination of resin. Note that it is positive failure - there is extra metal because the investment has failed, mostly. Yes, failed investment can mix with the metal and thence becomes porosity. This is common with 3D resins and the pics are pretty definitive.

The point. Hello Formlabs - you say your resin is castable and it sort of is and sort of isn’t. So what is to be done? It’s not a rhetorical question.


Hi @jjdon,

I’m sorry to see you’ve been having casting issues. My team has been working on understanding this issue for the past several months, which seems to appear with some users in certain combinations of burnout conditions.

We are developing updated burnout instructions for Castable Wax, which should allow for more leeway when casting bulky patterns, and generally make investment spalling (those frustrating rough surfaces) far less likely.

This new burnout schedule will be shared widely once we have tested it thoroughly - but I’d be happy to share individually with anyone who is having casting issues. In general, we are seeing lower casting success than in the past with R&R investments and have been validating Certus Prestige Optima as an alternative.

I’ll reach out via private message to get the specifics of your setup and see if I can help. If anyone else is having similar issues, feel free to send me a PM and I’ll contact you as well.


Thanks Amos, we’d like that. Even one failure is too many, as I said - this is not a hobby for us. We are using old school methods - Satincast 20 until stock runs out (they quit making it…) Across the hall tried R&R with no better results. No wax wash on resin because we’ve had problems with that, too. Vacuum the investment mix before and after filing the flask, burnout overnight and we’ve been ramping per your specs with your resin. Casting is oxy acetyline @ 900or 1000F flask, rest 10 minutes before quench. We cast the same gold ring as the pic this morning after 4 hours in a nail UV setup and it is MUCH improved. I don’t know how to PM you - email me at jjdon@pacbell.net if you will share your schedule. In return I will send you a paper my friend wrote for The Santa Fe Symposium with some interesting tests and thoughts about this very topic. Maybe not news to you but certainly interesting. Sorry, I don’t really have permission for wider sharing Thanks, John


Hi Amos, could you please send me that updated burnout schedule as well as any info available on the prestige optima as I have been having some pretty bad issues with spalling and failed casts i.e not getting full burnouts investment breaking down and embedding into the silver etc.


Any updates on this? I haven’t cast in awhile, but would really like to see a recommended schedule and details that work consistently.

And if it’s air flow, I’d love to hear what solutions people are using to increase airflow. I saw someone mention an aquarium pump with stainless tubing…I’ve seen another system from a kiln manufacturer. If someone has a setup that’s working consistenly, please, please share. I already upgraded my kiln to a larger one…


hmm, that’s unusual. I normally find gold just as easy to cast as silver. Perhaps it could be an issue with flask temp and/or metal temp when casting? What temp are you holding your flask at and do you use a torch to cast with or an electromelt?


Hi Amos,

We too have had poor success with casting. Please email me if you’re still available to help


@rji5668 Can I pick your brain on your casting process?