We are using an H-Bot gantry system. It should work better than the cartesian because the moving load is now lighter. 

We 3d printed most of the parts to set the system on the air hockey table. The setup was relatively straightforward: we have 2 steel linear rods serving as the vertical rails. For the horizontal rails, we are using carbon fiber tubes which we deliberately chose because they are lighter than the steel linear rods.  The horizontal rail system and slides along the vertical rails with lienar bearings to reduce friction. The pusher is zip tied to bushings that slide along the horizontal rails.