So, The Bluecast… How is the post-print shrinkage? Are you casting immediately as they recommend or taking your time? Seeing your pieces I’m sure you understand the issue here.
I was going to try this stuff but the shrinkage issue has me stalled.
Bob
I have been making the models 2.5% larger in preform. Sizes have been dead on.
Sometimes I cast right away. Sometimes a few days later. Have not had that be a problem yet
Art
I’ve found bluecast to have a variable shrinkage rate, depending on environment and time from print to investment. In the summer, I was losing 1 ring size from the original model to the cast piece. In winter, that went down to half-a-size. However, I get these results only if I print, rinse/dry/repeat 3 times, and then invest on the same day - preferably right away.
If I leave a print for a day or two - even in a drawer or dark cupboard, there’s a noticeable shrinkage.
I now only use bluecast for models where precision isn’t totally required - like pendants without gem settings, or prototype models. For anything else, I go back to formlabs castable. (I’ve found by properly curing my prints, using R&R Plasticast - finally available in the UK - drying my invested flasks overnight at 20°C and holding the oven initially during burnout at 143°C for 2 hours, I’m getting great, non-porous results).
I am using the previous version of BlueCast, and there is a little shrinkage if I leave the model sitting around for a day or so. If I invest within a couple hours, I don’t have a problem with shrinkage.
I don’t have a set percentage, but I’ll add about 0.2-0.3mm to the size of stones, for example. Following that, I can usually bezel-set a stone with little to no cleanup.
I’m in Austin, Texas…we probably sit more on the humid side of the spectrum. I understand that BlueCast is “hygroscopic” and seeks water…
I understand the new version of BlueCast is supposed to have addressed the shrinkage issue.
@Charles_McManus, are you also getting successful casts from the Castable V2? If so, do you mind telling us what burnout you’re using…and what type of casting setup you’re using? Many thanks!
No problem.
I’ve experimented endlessly with different investment powders, burnouts, etc. I’m on the east coast of Scotland, and differences in temp and humidity make a huge difference. What works for me is the following (with Castable V2):
-Print the model (I was getting good results with my formlabs 1+. Since upgrading to a form2, I’ve found the results even better).
-Rinse in dirty then clean iso. Dry with an airbrush. Stick in curing chamber for 4-8 hours, depending on thickness.
-Invest in R&R plasticast. Seriously. I’ve tried 4 other investment powders. Nothing else comes close.
-Place the flasks in a steady, room temp environment overnight.
-Warm your oven up to 143°C for an hour. Put the flasks in. Burnout at:
143°C - 2 hours
177°C - 30 mins
ramp up to 750°C at 200°C an hour - hold for 4 hours
Ramp down to casting temp. Flip flasks to let any carbon monoxide escape. Leave to settle for 3 hours. Cast.
My setup is pretty old-school. A large oven, an electro melt, a vacuum pump and chamber, and a MAP torch to cover the metal as it’s pouring.
It’s not always perfect, but I get more successes than failures these days. You can check out my work at www.circinn-studio.com to see the kind of stuff we’ve been casting.
Paul
thanks for posting the side by sides. Have had good success with the blue cast. Had the same issues with the FL castable… Also kike that i don’t have to cure the bluecast
art
I’m a huge fan of not having to cure, and having good results with BlueCast, but am going to go back and apply what I’ve learned over the past year to my Castable V2 and see how it works.
Paul, I’m wondering if a longer burnout would work on the Castable V2 version? There was one of your other rings that might have had residue (one of the heavier signet rings).
Thanks so much for showing them side-by-side!
Converting for those of us who live in a backwards country that never embraced the elegant metric system:
143°C is 290°F for two hours
177°C is 350°F for 30 minutes
1382°F for 4 hours (392°F/hr ramp)
Ramp down to casting temperature (I’m using 975°F for general casting).
Thanks so much, @Charles_McManus!
You’re welcome.
I have more news. So, I use the same vacuum setup for investing and casting. The other day, I’m casting. My vacuum pump is a heavy duty model that cost me quite a few pennies. It stops pulling a vacuum. I shrug, figure it needs the oil changed (probably clogged with investment particles) and switch over to my backup pump (about 2/3 the strength of the big bubba). I have a lot of commissions to get through, so I put the big pump on the to-do list of future Charlie and carry on.
My next 2 casts are terrible. Really bad - orange peel, porosity, and flashing. Not just the formlabs, but the wax models too. I adjust my burnout schedule to a slower ramp, etc. but it’s even worse. So, I email R&R and get no response. Finally, I download the datasheet for plasticast, and find the answer: The initial degas of the investment has to happen in under 2 minutes. Normally, that’s fine, but with my smaller pump, it’s closer to 3 minutes. Plasticast does not like that. It especially does not like me reducing the amount of time I’m mixing the investment so I can pull a full vacuum on the slurry.
Long story short - the quicker you can get a collapse on your initial degas of your slurry, the better your casts are going to be.
I don’t think this is true of all investment powders - I’ve tried 4 so far with this resin. However, it does appear to be true of the R&R plasticast. The bigger your pump, the smaller your chamber, the better.
Interesting observation…I read the R&R instructions awhile back, but never noticed anything about that.
Charles, do you know what your elevation is? I’m in Austin, at 489 feet from sea level, or 150 meters. When I was in Denver (5290 feet, 1612 meters), I know that my pump acted differently, although I’ve been back in Austin for almost three years. Mine’s a Kaya-Cast, but I’m guessing that doesn’t have a “bad boy” pump!
Other than a larger pump, is there any other way to affect the speed? I saw you said “smaller chamber.”
I’ve actually never timed the initial degassing. I’ll do that on my next casting session.
Thank you for the info on the plasticast Charles, I did not know about the quicker the degassing the better the casting, I do believe the harder you mix the investment the harder the investment will be , I don’t have any proof of this but I do mix as vigorously as I can. I always make sure there is no investment residue in the flasks or bases, someone told me along the way that the residue can cause the investment to set inconsistently, the people that work for me probably get tired of me reminding them.
Cheers, Paul. I hadn’t heard that about the investment residue. I’m off to scrub all my flasks!
I totally feel your pain and frustration on this one - I’ve been experimenting with Castable V1 and V2 for about 2 years now, and it’s only now I’m getting consistent results, and only after tweaking and trialing every stage of the casting process.
Here’s the document I found on plasticast. Step 6 is where it talks about degassing:
@katkramer, I’m 44m above sea level. I know what you mean - the weather changes quite a bit here on the east coast of Scotland, and I find my casting setup needs to be tweaked in Autumn and Spring. My big pump pulls at 12CFM, which means it creates a 99.9% vacuum in a 30L chamber in a little over a minute. Before buying a bigger pump or a small vacuum pot, you can try displacing the air in your current setup - e.g. if you have enough space in the bottom of your vacuum pot for 2 bricks, then put 2 bricks in there - the air that their mass has displaced is air you don’t have to pump out of your chamber, and should speed up your degas. Just an example, but you get the idea. I would definitely time your degas.
It took me a long time to get the times and mixes right on the plasticast. The mfg instructions did not work for me at all. I had to add more water than they recommended and cut down vacuum times and mixing times… Took me awh
ile but finally have good castings
Paul, the 1800°F burnout is too hot, according to R&R. They’re reasoning was “investment breakdown” but also that there’s not enough oxygen at that temperature to completely eliminate the ash. They say that the investment breaks down at a certain temperature (I’ll have to look it up, but I know that the recommended burnout temp from BlueCast was WAY too hot according to R&R’s engineer. They recommended going back down to 1350°F and holding longer (732°C). My thought on the crud on the top of the Sober Riders ring is that it’s ash residue. I’d try 4 hours.
I had heard something from a glass casting instructor about investment (plaster) residue in mixing bowls and tools causing plaster to “flash set” and set too soon. That would make sense with what you’re saying.
I’m casting on a small scale, so I just use a KitchenAid hand mixer in a rubber bowl, then degas in my combination vacuum caster. I’m not really fussy about it…I’m mixing at the 40:100 ratio, and mix more or less for three minutes (depends on if I have my Apple Watch handy to time it), and mix on the highest setting.
In glass casting, we let the investment/plaster mixture “slake” and let all the liquid combine before mixing. With R&R Plasticast I’ve finally gotten over that and just jump right in with the mixer. I’m also not paying any attention to using a separate timing for the initial mixing…as soon as I get the powder in the bowl, I start mixing, and count that as part of the three minutes.
I would say my recent casts have had no “general” porosity or “scaliness” like my earlier casts, but I have had a couple small pits that are consistent across casts…I usually cast three of each model, which I then pick the best, finish, then make a rubber mold. I have noticed on a couple models that I get a small pit in the same place on each one, which makes me thing it has something to do with the sprue placement. That said, I’m also not doing the same kind of models as Paul…mine are more like charms and basic rings with a single, if any, stones.
I hold the plasticast at 1375F for 4 hours. then cast at 900 flask temp. When i went higher I has investment breakdown. Fo mixing, I use a electric hand mixer for 2.5 minutes. The 3 recommended was too long and it was getting gummy. I also only vacuum for 30 seconds after the break and 1 minute 15 sec in the flask.
I’m sorry, I had to look it up, that’s what happens when you get a bit older… didn’t believe it either
I was using allcast investment for the platinum casting, you can run the burnout to 1800 Fahrenheit for a 30 minuet hold and then I was casting at 800 Fahrenheit, I only ran about 10 flasks using this product, it’s been just one year , the investment is extremely hard both before and after , they also recommend using allcast investment precoat , that helped alleviate the bubbles on the casting, I won’t waste your time right now with all the stuff that went along with casting the platinum,
It is what is recommended for using with the TI machine, there were issues other than the investment, it worked good and when I attack it again it’s what I will use , I ordered the material from Gesswein and it is what my metals supplier recommended
Burning out at that temperature didn’t change the results of the castings printed with the FL V2
Note of interest the allcast precoating makes a very good mask for powder coating, best I have found for jewelry
Wow! A 30-minute hold sounds divine!
It is sort of nice , but the whole casting of platinum is difficult , its hot, really hot, when the platinum was up to casting temp the room was literally glowing. It was 3 ounces and it took about a full 5 minutes to melt it using propane and oxygen, I used the crucible recommended by the folks that make the TI casting machine and I used a new crucible each time because heating it that much for that long just about burned through the bottom of it. One of the problems I saw in the cast piece was some really fine dendritic porosity , I think it was coming from the crucible , or that’s what I thought, I’m wondering now if it was actually coming from the poor burnout. The propane and oxygen is clean and the only other choice to use is hydrogen , I just haven’t wanted to invest in that torch.
Now that I understand one of the problems I was having is the poor burnout of the model, I’m going to start over using the Bluecast and figure it out, things will start slowing down in April or so and Ill have some time, if anyone has any experience with this I would be real happy to hear about it, in the mean time I’ll post how it goes
first Kerr is out of business. Buy plasticast band-d from gesswien.
