Need casting Help!


#1

So we purchased the Form3 printer around March April this year. printing is going great! no issues there. its the burnout schedule we are having issues with. We are using the purple castable wax resin, washed twice in IPA, dried before spruing, investment is R&R Plasticast, mixed at a 40:1 ratio. After mixing, its vacuumed, poured into the flask, (2.5x3) vacuumed again. Left to set up untouched for 4 hours. Placed in room temp kiln (usually around 70-77F) First we ramp up 5 degrees F/Min to 300F (holding for 3 hours), next ramp is 72 degrees F/Min to 1450F hold for 4 hours. Ramp down 72F/Min to 1250. The pieces are not overly heavy but have some fine filigree work. Casting with new casting grain, 14k white, 14ky, and 10ky. Im used to casting wax models with no issues, now casting these resins, I can’t seem to find a medium here. Some have come out okay, while others have seemed to fallen short. Seeing everything from porosity, to fine yellow powder from ash residue, incomplete castings messing with can tempetures raising and lowering. Does anyone have a solid idea of a burnout schedule. Also we are introducing air into the kiln during burnout. using an air compressor pumping lest then 1psi of air. does anyone have a lead on recommended air flow needed to provide a solid burnout? to little air we get the ash residue, to much air the kiln doesn’t reach tempeture. I don’t know what to do anymore, I’m pulling my hair out.


#2

Some possible ideas, to take with a grain of salt. Hopefully some other people will chime in with schedules and airflow recommendations as well:
-Could you use kiln furniture to help make sure the flask openings are exposed to and facing the air flow if necessary?
-Increase the length of time it stays hot (in my opinion, above 950F or so), whether that’s your 1450 hold or holding at 1250, to give the material even more time to burn out, no matter your air situation.
-Running your compressed air through a flowmeter with a valve and floating ball bearing that reads in CFM or similar units may help you to adjust your airflow to a consistent level
-If you can afford the time and effort, compare results with one flask at a time, taking note of where in the kiln the flask is, whether it’s facing up or down or sideways, whether it’s near the air-input or the chimney, etc.
-I think porosity may indicate too fast of an initial heatup.
-Residue, ash, and weird yellow powder are probably all incomplete burnout, from not enough heat, time, and/or air.


#3

One thing I was told by the Ransom and Randolph folks is that the hotter temperature with burnout at 1450°F reduces the amount of oxygen. They recommended the regular number of hours at 1350°F, or even a little longer.