Prusa i3 MK2 as a plotter

I wanted to label a CD and had only my Prusa i3 MK2 3D printer on hand. Since I didn't wanted to create a permanent installation I designed this part to simply slip over the extruder stepper motor. As it turned out I did not need a screw at all to clamp the holder to the stepper motor - it works fine only by friction. The pen is held in place by some holders which I hot glued on.

It uses two rubber bands to hold the pen. This works better than I expected since the rubber band gives enough fl