I have used ProtoMold and they are very good. They are aluminum molds and there are fewer options with regards to custom details, but if you are making basic pa

I have used ProtoMold and they are very good. They are aluminum molds and there are fewer options with regards to custom details, but if you are making basic parts it works fine. I would think it would work very well for injection molding parts for a 3D printer because surface finish is probably not critical and the quantity will be relatively low. I generally think of the scaling up process as 3D printing -> ProtoMold -> steel molds. That said, when he said $50k in molds, I pictures $50k in ProtoMold molds, not $50k in steel molds. I imagine steel molds would be more on the order of $250k.