>I wonder if you could have a something that squirts a fine jet of liquid nitrogen, just behind the print head? Expensive though I suppose. Maybe - just a semi

>I wonder if you could have a something that squirts a fine jet of liquid nitrogen, just behind the print head? Expensive though I suppose. Maybe - just a semi-random idea, mind you - a Ranque-Hirsch (or Vortex) tube (and a source of compressed air) would be enough and possiby be more practical: https://en.wikipedia.org/wiki/Vortex_tube https://en.wikipedia.org/wiki/Vortex_tube