[bsder]

Why? You just 3D print steel ones.

You use the metal sintering printer to deposit the metal. Then you use an in-envelope milling head to polish it.

The cooling can be conformal since the shape isn't limited by milling technology. And, since molds have a lead time of at least 6 weeks (and generally worse because something always goes wrong), speed isn't the issue.

There was a good talk at Molding 2018 by the CEO of a Silicon Valley medical prototyping company about how his folks simply won't deal with conventional molds anymore and he has bought 3 of the 3D metal printers with in-envelope milling heads.

Unfortunately, the Molding conference website is a dumpster fire for useful technical information. If I can remember the name of the company, I'll reply.