Water-soluble mold for cast-metal Benchy

You can find full instructions for slicing, printing, and casting here.  In addition to the setup detailed at that link, for this model I recommend maximum support overhang of 45° in order to adequately support the mold. The image shows the printed mold in translucent gray and metal part after casting in blue.

The mold and support are printed from PVA (or other water-soluble filament), a readily available low melting point alloy poured into the printed mold, and then the mold and support are dissolved away in hot water. This allows complex metal pieces to be cast requiring no special equipment beyond a 3d printer and an ordinary hot plate to melt the alloy.

It may seem surprising that you can make a metal casting using a plastic mold, but the metal used is a low-melting point alloy of tin and bismuth (essentially a relative of pewter), and the metal cools quickly on contact with the mold before it has a chance to deform.

After casting and dissolving away the mold you snip off the feed and vents from the part. The metal part can then be filed, sanded, polished, and plated if desired. In the picture below the cast parts are variously unfinished, polished, copper-plated, nickel-plated, or anodized. You can find many of these in this collection.