Filament Protector

My solution was to avoid the hole altogether.   I had another idea for a filament guide for the sideways mounted spool on the back.  It would just be a collar to fit inside the hole with an inner diameter sized to hold a short length of clear tubing.  The tube would extend out the back just past the edge of the spool, and far enough inside to keep it off the edge of the frame.

For printers with cases, I think some kind of filament guide for the top of the extruder would be good.  I had some trouble with the S1 with the filament getting kinked into a 90 degree bend on top of the extruder while the case was on.  There is only 12mm of clearance above the extruder, so the filament has to make a fairly sharp turn.  Something on top of the extruder that maintains the largest possible bend would help keep the filament from getting pulled down flat and kinked by forward movements. 

Having the motor cooled will help keep the filament from getting softened too much on the way to the extruder, but on long, enclosed prints there might be enough heat buildup at the top to be a problem.  When my case comes in I'll tape my thermocouple up there and see what happens.

what about a product like rubber dip or even the rubber spray.
You buy it in small cans and you can dip your tool handles etc in it to create a rubber handle.
You could use the spray locally on the hole cutout for the filament. Would create a soft edge for the filament to run by...

and perhaps add this to remove abs dust on the filament.. It can be attached anywhere on the filament.

http://www.thingiverse.com/thing:16483