About 13 years ago, ealdthryth worked for a startup company that built 3D printers that used a recyclable thermoplastic in the printers to build models. They closed down just as the machines became viable.... It was pretty neat technology and great because everything else on the market used lasers and/or toxic resins.... It was relatively afforabable (I think about $10K or under at the time). We've still got a few of the really delicate structures the test printers built.

But the technology (and computer hardware) have become mature enough that I've seen kits to build your own 3D printer.