This piece is a remix of my both previous extruders / feeders:
I really liked the design of the first one (except the cover fixation) but it required to reverse your stepper motor wires (and not everybody is ready to do it) + to be honest, it maybe not push enough the filament to the cog wheel.
I never liked the design of the second, but it was fully functional... Maybe too much, because the spring is very compressed and so, I've broke one: The mobile part was too thin. Also, it was a bit hard to mount, but no need to change stepper motor's wires.
This version get the best of those extruders / feeders:
- nice and clean (IMHO)
- supports flexible filaments
- supports a decent runout switch
- easy to print
- easy to mount
- Its cover stays in place, even when opened
An alternative base / support is included in the STL files: It allows you to mount the extruder on your aluminium profile, because I'm planning to mount mine on the top of my printer. For now, I didn't test this alternative but only the classic one (with success).
FYI, I'm using this kind of microswitch:
(you can find all dimensions in the FreeCAD file if you want to check)