I had very bad curling problems while trying to print the sun gears in ABS... the overhanging cone in the center kept curling up and then the extruder would hit it. I realized it only curled away from the brake tab, because the brake tab was holding it from curling. So as a solution, I added 2 more brake tabs, I also widened the small part of the cone just a little bit to reduce the overhang distance. I also had problems with the gear teeth curling up from the platform, so I printed them with a brim in slic3r and that solved the problem, trimming the brim off was not too hard, as I made it wide enough (6mm) so I could just grab it and pull it away from the gear. This is posted as a work in progress because I am still printing the rest of the parts to assemble this and I'm not completely sure there will be clearance for 3 brake tabs, although it appears to be fine in openscad.Update: I have my transmission model finished and assembled and these gears are working great with it!Print these Sun Gears with 3 Tabs when using ABS. These were printed with a single extruder head pausing and changing colors after layer 5.