Just made this simple direct-drive extruder for my homemade MDF 3d printer.
Minimal hardware requirement, M3 X5 screws, M4 X12 screw, M4 washers and 15mm OD, 5mm thick, 4mm ID ball bearing.
There is no adjustment on filament grab pressure because over the time I realized that it was not necessary once you are set right.
Fits Nema 17 motor, E3DV6 clone, 40mm fan, MK8 extruder drive gear and 1.75mm filament.