The pictures and parts should be enough to see how to build the robotic arm.  The base motor is a NEMA 23 rated with enough  torque to rotate all the weight carried by the arm.  The next motor should be the strongest a NEMA 23 stepper motorwith more torque powerful enough to lift the arm and end weights.  The third servo motor is a NEMA17 stepper motor probably as powerful as you can buy.  Finally, the gripper is whatever gripper or other tool you want to use.  

To get the arms to hold to the stepper motor axles I will use Gorilla Glue for initial testing.  This way I don't have to buy hub clamps, although after testing,  then I will redesign the "Spinners" to accommodate the hub clamps.  

This kit is designed to work with a RoboGuts™ circuit board and three or more Stepper Motor Drivers.  http://www.R2Pv1.com/ 

I'll add a gripper plate after I 3D print the robotic arm for myself first and do a few tests first.  I want to see how much the arm will lift to determine the gripper needed to pick up the weight.