I was talking more about using a 3d printer to make a mold, then melting down metals to create your own castings. A small foundry kit where the printer makes the mould, you pack the sand, then you melt down alumnium cans or scrap steel, pour and get yourself a metal object.
Now if we can get low-cost printers for metal and electronics, and on-the-spot recycling for at least the metals, we'd be there.