Ahh yes my first instructable. Here goes nothing. This instructable is going to cover a method for casting in 3d printed plastic. The casting material I went with is castable refractory cement. First print your mold. Keep in mind that you have to split the mold so you may want to make some channels to cut along. Second get some Crisco baking shorting. I don't know if any oil based product will work but this is what I went with. Apply the shorting to you mold. You want to apply it so its shinny, but not white. If you cast with it being white it will take out alot of the shape and may even make the cast incomplete. Next measure out your refractory cement. I go with a 1:1 ratio. The mold I used needed 2oz mix to 2 tsp of water. You may need to alter this as its pretty variable. Next put the cement in the mold. A trick to getting out the air bubbles is to tap it a few good times on a table so the mixture settles. Let it dry, then cut the mold off.
Descriptions of pictures
1st Selected mold
2nd Separating compound (crisco baking shortning??)
3rd Apply separating compound
7th Pour (2nd run)
8th Final product after removing (2nd run)