Let me start by saying that this ArmDrive Bowden Extruder setup is one of the best Bowden driven system I have personally tried. It's so simple, yet very reliable and effective. Even though the designer tried to beef up the filament entry guide, PLA is still very rough and it will still wear down eventually. What I've done is to beef it up a little bit more and opened up the hole so that you could slide a piece of teflon tube in there to eliminate the wear & tear to the printed part altogether.