I am totally not kidding about the safety/protective equipment. When I was young and dumb I did a pour on concrete. Some of the aluminum overflowed and when it hit the concrete, even though it had been poured 20 years earlier and we hadn't had rain in months, the concrete exploded like a landmine and I got to watch a drip of molten aluminum run down my face shield briefly before it froze. Ever since then I pour over dirt or sand.

One nice thing about 3d prints is you can break them into pieces if you need something bigger than your printer. Just print it in eight chunks that snap together and use wax to smooth the seams. Similarly you can print complex cored molds. I keep thinking about casting an OHV crossflow A-series head. Print the lower section including the chambers, place a pre-formed core for all the oil passages into it, and snap on the top section that has the lower bearing halves for the rocker. It's like green sand casting without the need for draft angles on everything, and no need for split molds. You can even print core boxes for making the cores, albeit you can't bake a printed core box so that'd have to be sodium silicate and CO2 cured.