The article says it's an extrusion printer, so gravity isn't needed. Current machines would probably work without further modification (e.g. as others have note

The article says it's an extrusion printer, so gravity isn't needed. Current machines would probably work without further modification (e.g. as others have noted, the RepRap can print upside down). In terms of what parts can be made, multi-material machines are commercially available[1] that allow a selective distribution of material properties throughout the printed object. This gives the ability to print quite advanced objects, not just dumb plastic parts. Add to that the developing abilities to print electrical circuitry, and you'e approaching a very useful ability and source of replacements. [1] http://www.objet.com/3D-Printer/Objet_Connex_Family/ http://www.objet.com/3D-Printer/Objet_Connex_Family/