There are many filament spools on Thingiverse already. But when I didn't find one that was 100% printable, I couldn't resist the urge to design my own. This is my first design so please be gentle.
I started with thingiverse.com/thing:4337 but I had trouble getting a good print, and the bearing rollers (from thingiverse.com/thing:4312) popped out. I decided to experiment with a different kind of roller: instead of a sphere, I would use a cylinder capped by two 45 degree cones. I figured this would print better on a makerbot; my spherical rollers ended up teardrop-shaped, and when they turned sideways they would get wedged in position. The inner cavity of this bearing should theoretically prevent that, though in practice the tolerances here are way way too loose. (As a side bonus, it's much easier to clean.)
I stole the the extend-o rod idea from thingiverse.com/thing:5551 .
Future work: The hub ought to be tightened up and it has lots of excess plastic. Also skeinforge35 doesn't handle it too well; when I print it the inner hub is hollow and has no bottom. Luckily there's enough extra string floating around that it still works okay.
The hub and spokes are designed to be printed raftlessly. I had some curling problems with the extenders, so I rafted them.
Print 1x mount, 1x hub, 4x spoke. This will get you out to a radius of 100mm. For another 80mm (which nicely holds the roll of filament that came with my Thingomatic), print a set of 4x extender.
Cleaning the hub:
- There's a miniature annular raft between the inner hub and outer hub; this helps the rollers get seated properly on their points. Cut or peel this away.
- Take out your pocketknife and insert the blade into the annular hole at a 45 degree angle facing outwards. Run it around the outer perimiter of hole to cut all the strings.
- Turn the knife 45 degrees inwards and run it around the inner perimeter of the annular hole.
- Turn the hub over and do steps 2 and 3 again.
- Wiggle your knife between each of the balls and pry them loose from each other.
- Spinning the hub for a while (e.g. by chucking it into a drill) will make it turn more smoothly.
The 4 spokes should slide into the hub, with the optional extensions. If they need a little persuasion, tap them with a hammer.
The mount replaces one of the extra two z-endstops on your Thing-o-Matic and hangs off the front. The hub's center square hole mates with the end of the mount. The holes in the mount may print out a bit small for your M3 bolts; if so drill them out.
Once it's mounted, put the filament onto the spool and pull the loose end around until it's nice and tight. I taped my loose end to one of the spokes to keep everything neat, but this is probably not necessary.