A related method not mentioned in this article (or, in fact, many places at all) is iro3d[1]'s "selective powder deposition": a 3D printer effectively creates a mold out of sand, with empty spaces filled with a metal powder. After the "print", done in a crucible, is finished, an ingot of metal with a lower melting point is set on top & the whole thing
baked in a kiln. The metal from top fills the space between the granules of powder and solidifies with nearly no shrinkage (as the object is mostly made of the powder, which never melts).