Pure copper casting under pressure in a metallic mold is really a pain and you won't find any people to do that IMO. We casted some WB using wax molds under partial vacuum because 2 foundries refused to use pure copper in their injection machine with our metallic mold to avoid their "destruction". Pure copper is too viscous and you need to heat more than its fusion temperature at 1083°C to help liquefaction (or put some metallic powders to help it but alloys are bad in thermal conductivity), machines are too much limited... If you ask a founder what is the worst metal to work with, you can be sure than pure copper will be one of them. So we used traditionnal method by hands but results were too much disparate, control is too much limited over the ~40 WB made in a single shot, expected quality wasn't there. Silver is easier to use than copper.
SLS and stereolitho help to make beautiful 3D metallic shapes but porosity could be too high for some applications.
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