Polyamide plastic will apparently break down with water exposure, so this rules out gypsum molds. I'm curious if anyone here knows whether two-part silicone putty or other material would work with polyamide? I know this can be done with PLA. My end goal is casting a silicone puppet, but I have no problem making an intermediate cast in wax to accomplish this. (This sounds convoluted, but I happen to have both a printable sculpt from a CG project and access to a commercial laser sintering printer...)
Didn't know that about the water. You could coat it with something to seal it first. I had to do that to make a polyester resin fibreglass mould from a big water-based clay sculpture once, because polyester won't cure in contact with moisture. I used a 2-part floor varnish, then wax and pva release.
But if the plastic print is a hard material you probably don't want a plaster mould anyway. Unless it's a very simple smooth shape, there would be undercuts, and you might need a lot of pieces. You can make silicone casts in silicone moulds, with release agent. But I would probably go with the intermediate cast too.
I would test the silicone on a scrap of the polyamide plastic first - not so much because I think the plastic would break down, but because there are a lot of things that will inhibit the cure of the platinum cure silicones. I made a little texture stamp from the leathergrained part of my old Bolex camera, which worked fine, but the same batch of silicone on the leathergrained plastic surface of my Nikon DSLR stayed liquid, never cured at all. And although I cleaned it 6 different ways, there's still a faint blotch on the camera that I can't get rid of.
Thanks for the response, Nick! I get a feeling this will be a sticky mess, but trial and error it is...