Printing spheres...

I don't know if this has been asked before, but is there a trick to being able to print a sphere with the M200? So far I haven't been able to get a good result. Either the base of the sphere will end up flat or the layers won't stick together and the sphere breaks into pieces. I've tried printing Triple Ball Bearings (http://www.thingiverse.com/thing:51806) multiple times (even with Z-ULTRAT) and Zortrax's own Ferris Wheel ( http://www.thingiverse.com/thing:384550 ) and ended up with poor results. The Ferris Wheel bearings kind of work, but the other part is unusable.