How is 3D printing done in space?
Most likely, the 3D-printers used on ISS does not incorporate some fundamental difference that allow them to print in zero gravity.

Some people over at 3Dprint.com raised a very similar question, and figured that when turning their 3D-printer upside down and on it's side:


  there’s not really much difference at all. It’s quite interesting to see how the orientation has little effect on the quality.


One of the early 3D-printer models - the Bukito printer - demonstrated that their printer was so portable it even could print on the move, and upside down.

In other words, some consumer 3D printers already print upside down, and so they would probably print in zero gravity as well!

(That's the short story anyway. Have a look at Ryan's post, who gives a great description of the more intricate parts of space printing!)