MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
I would think its possible to extrude a 'C' shaped filament and put a cap on it after filling it, the powder could be ground to consistent size I assume, and it's free. Filament could be similar to a pencil, would need to be a larger diameter, but then, maybe larger scale stuff can be realized. Maybe some sort of mixer as it extrudes.