Haha, been there, done that already 
I built my own electric furnace and then tried lost PLA and also a year later sand casting using PLA plugs.
Check here if you want to see how I built it, it’s really not that hard to make. A fun little project anyone can build in a few days:
Here’s the result I got with sand casting:
Making the mold, which is the difficult part:
But actually, it’s funny you should mention that, because I’m about to do it again in order to cast some aluminum brackets for my new motorbike (which made its first wheel spins yesterday BTW, yay!)