ABS master, from Mike's Makerbot - this is actually a half-scale print of drayde's Thingiverse propeller - http://www.thingiverse.com/thing:3678
Set up with wax sprues and vents
In a bit of plastic pipe
And filled with investment
Copper and 10% tin
Burnout: 3 hours at 150C, 30 mins at 500C (this phase is smoky), 30 mins at 700C.
This investment split due (I think) to waiting too long to begin burnout. And perhaps also due to pouring into a split plastic pipe, not a stainless steel flask. Amazingly, it did not hurt the castings.
Two of the fins cast pretty well, two did not. I think the fins were printed slightly hollow and filled with investment. You can see the print texture under where the fin should be.
And there's a void. Air bubble or flux inclusion ?
Cleaned and lightly polished.