Redesigned lower arm for shanes extruder

This is a simple tweak to Shanes Armdrive extruder.
I brought the guide section for the filament as close as possible to the gear/bearing, so it just barely has room to open with the quick release.

Printing this in 0.1mm layer height with PETG, resulted in a very strong even in the very thin section between the bearing/gear.

Using this i am able to print TPU at about 30 mm/sec reliably.