I found interest video as follow :

It was time to move away from printing solid objects and try to print moving objects. In this video I scale up a planetary gear set (transmission) that I picked up from thingiverse.com and I scaled it up to 200% to make it larger for a better demonstration. The end result after printing for 15 hours and a little cleanup is a functional hand crankable (or drill crankable) planetary gearbox. I can expand this gearbox to include as many series of planets as I want to reduce the gearing even more. Let me know if you guys enjoy the video and I will create more gear sets and do a follow-up on this! Also the video contains a cool trick I learned for easily detaching prints from the build surface which can be a complete pain so watch the whole thing! Thingiverse Project http://www.thingiverse.com/thing:23030 Tiny Planetary Gears Set by aubenc is licensed under the Creative Commons – Public Domain Dedication license.

http://www.robots-dreams.com/page/4