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.
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.
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.