I'm working on two arduino (one a dock, the other one on a robot) communicating through a IR to let the latter know about its location.

I 3D printed a piece which goal was to channel the 3 IR led lights, to prevent them from overlapsing (exactly in the same manner as the [Kobuki](http://wiki.ros.org/kobuki/Tutorials/Testing%20Automatic%20Docking).

For a reason I don't know, the IR signals seem to go through the 3D printed piece which doesn't seem to let visible light through.

I known that there is no 100% absorbant materials, and I know "black for visible lights" doesn't necessarily mean "black for IR lights".

I think my problem is more related to my lack of experience in the field. My question is : why do I get signals from a IR led channeled toward a location I am not in ? 

Patently, it means my light channels are not channeling light.

Therefore, better : How can I make a better (and cheap) channel for IR light ?

The piece I 3D printed is grey (silvery like I guess)

edit : to prevent incomprehension, i would like to clarify "channel". What I mean is to block all light "not going" in the right direction, whatever happens to that light. I apologize if it is not the word I should have used.