After version 4 (green) works quite well. I decided to stick with the basic design and improve this version instead of trying another approach.

I started with the Gripper and will work from top to bottom down the robot arm

http://chaozlabs.blogspot.com/2016/04/mantis-robot-arm-part-1-gripper.html

I will post a video about the part and a small article on my blog where all the links and part lists will be.