The trouble with 3D printing a ball bearing is that spheres don't adhere to the 45 degree rule, so they tend to print poorly, or if metal balls are used instead, then the bearing requires assembly. This is a new kind of bearing that can only be manufactured by 3D printing and comes preassembled.
It is a planetary gearset and functions like a cross between a needle bearing and a thrust bearing. No cage is required to keep the rollers in place, because their gearing keeps them perfectly spaced. The gears are all herringbone, which is why it cannot be disassembled and also why it can act as a thrust bearing. If you're wondering how well a 3D printed bearing could work under load, please check out my video: http://youtu.be/ZghwSBiM0sU
This design is fully parametric and made to be adjusted in the Customizer app to whatever you need. Thanks to aubenc for finding a problem in the first version.