This is a bit hard to explain, but I’ll try.
The problem is around the elbow, where the ubber arm is in 2 parts, where the part near the elbow, needs to follow (rotate with) the lower arm when it turns (rotate). But the part near the shoulder shall not.
PS: Just say if I’ll need to make a better explanation.
posting a few pictures may help explain exactly what you are meaning, this will help people better when trying to see exactly what the problem is
are you setting up this rig using armatures? if so then try looking for a tutorial on armature rigging, cant really help you till i have all the info
I’m using armature rigging
you need to make a better explanation.
or, better, attach your blend file and a hand draw plan of what you want to do. 
The sides on the two objects shall allways be parallel, no matter how the arm moves with the use of IK.
give both cube copy location with relative bones… do not use child of if you are using then…
hope this helps
thanks
Thanks for your advice draguu. I tried to do as you said (I think), and it allmost worked. In the following images show the arm bended at 2 different angles, 1 picture from the side and 1 from the front, for each angle. As you can see, it follows the rotation better when I extract the arm more. But I want it to follow the the rotation perfect, at any angle.
PS: 1 of the images show the constrain I have used, to make the cube follow the rotation.
sorry but i dont understands what you want buddy … explain it more… what you want to rotate and what you want to follow it
Okay here are some pictures of the real robot arm I want to rig. I have set it in different positions, so you can see at wich joints, it turns wich way. I hope these pictures gives a better understanding.
What is it? Sry, but I dont download anything, when I don’t have any idea of what it is.
aah its blender file … containing normal rig setup of robo hand
I have looked at the blend file, but it doesn’t seem to use what I need.
