58mm Spool Hub for Rigidbot PLA

This fits into the 56mm PLA spool that comes with the Rigidbot, allowing it to turn more smoothly. May work for others 56mm spool, but I have not tested it. You'll need to print two of these.

Similar to http://www.thingiverse.com/thing:403870 and http://www.thingiverse.com/thing:413467, but I like my design better! :-)