How to fix a rotation with bones I want to know how to fix rotation to simulate a (kind of) robotic arm, this way:

I have this mesh 
 

I try to use bones to move using the cylinders as pivots to move it like this 



Where "PIVOT" will be the handle to move all the parts 

There is for cubes with two holes, and three cylinders, 7 meshes in total, and the bones. 

But I only get this: 



I don't know how to respect the rotation around the cylinders as pivot for the cubes and move that cylinders on the Z axis, to create a "robotic arm" movement.
Enable a complete IK Chain from the top pivot bone to the last moving bone, then, in the Inverse Kinematics bones tab, lock all rotations on the little "Cylinders" bones, and lock all rotations except the axis you need on the big "Cubes" bones (in my example, Z axis, enable axis visualization if needed).