Filament cleaner for Ultimaker

-EDIT- I've taken the files to YouMagine.com since Makerbot has joined the dark side: http://www.openbeamusa.com/blog/2014/5/22/stay-classy-makerbot
https://www.youmagine.com/designs/filament-cleaner-for-ultimaker
It may be a good idea to lead your filament through a sponge to automatically clean off dust, hairs etc. Couldn't find one for my Ultimaker, so I made a very simple one with OpenSCAD. I think the sponge causes very little friction, so no issues with printing and retraction. I'll see how it goes, maybe change the design a bit.
Using the OpenSCAD-file it's very easy to change dimensions if it doesn't fit your printer or if you want a different thickness etc. I made some stl-files with and without screw attachment and square cutouts.