Update: 3D System has fixed the feature I was exploiting. But now you can purchase an adapter from http://www.cube3dfree.com/
You can still use the adapter and bulk spool holder.
The Cube is a solid little printer. It is very simple to use. There are barely any knobs to tweak. Its good for someone that just wants to reliably print things without babysitting the printer. The ABS does have warping issues even with the heated bed. The big problem is the filament razor blade model. The printer is not that expensive, but they charge $49/0.7lbs of filament! (compared to $31/2.2lbs of Octave 1.75mm filament). That is 5X the price!
It turns out that you can by-pass/defeat the Dallas Semiconductor 1-wire chip which is located in each cartridge. The chip stores the filament color, remaining amount, etc.
This adapter allows you to connect the plastic filament tube and then connect to a spool of generic filament. It was printed on the cube (version 1)
I now have a Lulzbot TAZ5. It can use a much larger range of exotic materials (rubber, wood, copper, magnetic iron). I can print large ABS parts and they don't warp. It is much easier to level the bed.
I'm still running experiments to compare the build quality using the Cube filament versus the different less expensive spool filaments.
I made a spool holder out of some 1/2 cpvc tubing:
1) three pieces of 6"
2) four pieces of 1"
3) two pieces of 3"
4) six T fittings
5) two 90 degree fittings
I hand drilled a hole so you can leave the cartridge filament hanging out. I will update the CAD models when I get the chance.