I did this type of casting in the early '80's for a shower fixture manufacturer. They bought a machine and system known as "spin-cast". For about $10k they got the whole thing and some start-up help. I made round molds with the masters. Molds were pressure baked silicone. The round molds were spun in a machine and the metal was poured in the center, centrifugal force took the metal through channels to the cavities. I made some prototype parts and some parts that they were already buying from other sources. Too bad, that's about as far as it went. Between decisions of what to do with it I copied some things for the experience. I made some great counterfeit quarters, twenty at a time.
Scott