Here is a modified version of Zach's Plastruder design. These layers replace the ones inside the MK4 plastruder to help guide the Idler Wheel. This keeps it straight and on target. I have managed to crush filament without so much as a crack on the acrylic idler wheel.
I still wouldnt recommend crushing filament just because you can...but this will atleast keep you from replacing an idler wheel every so often.
NOTE* The rendering engine on Thingiverse makes the files appear wobbly, but when loaded into the proper software they should show perfectly round.
Laser cut and replace each layer.