Robert Howle wrote:Been casting all the B9 castables since the beginning. I am now casting almost daily using Emerald Green.
This may not be for everyone but based on my work and the fact that I use to heat cure prints I have now gone to this burnout.
Using nothing but Ultravest Max, a broken arm casting machine, a 8 x 8 oven with holes drilled in the bottom for good air flow.
Pour flask, let bench set for 30 to 60 min. Put in a room temp oven and go:
Ramp to 350 F and hold 2 hrs. (this is to make sure the prints are really cured after being in the Model Cure)
Ramp to 1450 F as fast as possible, and hold for 2 hrs for med to smaller prints, and 3 hrs for heavy signets and the like.
Ramp to casting temp over 1 hr. hold for 1 hr or more and cast.
You have to have adequate air flow or u are doomed to have bad castings.
There is one more thing I do that i have forgotten to mention in the past. I "cup" the bottom of the flask after bench set to direct the max air flow to the main sprue at the bottom of the flask. I use a spoon or curved butter knife. All my flask are on expanded metal raised 1 1/4 inch off the oven floor. I use 3/4 inch nuts tacked together using the laser (2 stacked on top of each other, and there are six of these supporting the expanded metal).
Proper spruing is also a must. As I have said many times in the past, casting is as much art and technique as sience.
If u can't cast the Emerald or the Yellow it's your technique so don't blame the resin. There a hundreds of users casting the B9 resins everyday with great success.
You can read all the white papers u want but if u don't cure, sprue properly, have air flow, and reach the high end temp you won't be successful. Some are making this way more complicated than it is. When I have been casting these resins since the beginning and only used SatinCast and tap water, which I never even measured and mixed by eye, then it can't be that hard to do.
No reason to start mentioning things like: over heating the metal, dirty metal, incomplete mixing of the investment, improper vacuuming, spinning the broken arm machine too fast, pits in the spruing, sharp corners in the spruing, I could go on for quite some time. Technique, technique, technique. All these things apply to wax too, but it is just more forgiving.
Successful B9er since August of 2013 (version 1.1 when I began using cherry and Red mix for printing and SatinCast for investment and a 35 yr. old broken arm machine which is still in use today).
Robert does an excellent job of summing up the whole process. I totally agree with the emphasis on adequate air flow and the consequences (Doomed!) of inadequate air flow.
I was surprised he only lets the flask sit for 30-60 minutes. I recommend letting the envested flask sit undisturbed for at least 2 hours (I prefer 3 hours)... I like the envestment to be as hard as it can get before burnout.
I agree with everything else, 100%!!