One of my customers wanted a prototype of a handle with a metal tang inside. The original thought was to print everything in plastic, but I pointed out that the heft and balance of the prototype would not be realistic. Instead I suggested that we print the handle in plastic, and cast the tang in pot metal.

I printed a mold for the tang in PLA:

I then purchased some metal with a low melting temperature (about 160 F). This is what the mold looked like after I poured the hot metal into it:

I ended up with too much metal, as you ca see both above and below:

After a trip to the belt sander, the part was fine:

And this is the handle with the tang inserted: