First, yes, placing the entire printer in a 3DOF setup that would allow it to always use gravity to hold the filament straight would cover some aspects of reducing the need for support, but the greatest requirement is the ability to keep the extruder nozzle out of the way of different parts of the structure, that part is a terribly difficult set of calculations, reminds me of the shortest trip problem in Statistics 
. The difference between 3D printing and all of the aforementioned inertial navigation systems is that precision is quite relative. A typical 3D Printer shoots for around .01mm accuracy for the tool placement for the duration of the print. That is improbable with an inertial navigation system. A drone has the ability to correct itâs position via checking itâs inertial navigation system against GPS, thereâs not really anything accurate enough right now to allow you to do that on a 3D printer size scale. I imagine something like a 3D scanner guided 3D print head, and the costs start to skyrocket, LOL.
[quote=âgadget2020, post:7, topic:16067â]
Why canât the process be reversed and a skin be applied all round a skeleton?
[/quote]It could, if we could get the tool extruding the material into the areas required to make the skeleton. On a typical construction site, there are many âtoolsâ at work(Iâve met them 
) and all are smaller than the resulting structure. On the flip side, there are only one or two tools on a 3D printer, and they are much larger in relation to the material they are laying.
[quote=âgadget2020, post:7, topic:16067â]
Is the next step in 3D printing to be applying an ink/surface finish to a newly printed model?
[/quote]They have some powdered SLS like printers that spray a colored or clear glue to adhere layers of powder to form a model, on example is here. It would print without support as well.
[quote=âgadget2020, post:7, topic:16067â]
I watched a TED talk recently where they have a program that can take any shape and work out the folds to turn a single sheet of paper into that model⌠itâs rather impressive.
[/quote]Was the software open source? Sounds cool. I would like to have the ability to do that with sheet metal.