Based on the Coreystruder. My MK5 filament drive cracked and blew (see images), so I needed a printable replacement filament drive on the double. So I patched up the filament drive and printed this, a variation on the Coreystruder which was almost exactly what I needed. Changes include:

• Ribs on the motor side for better support
• Reduced vertex count on holes/edges to print better
• M5 screw/nut combo for tensioning the plunger, same as MK5 drive
• MK5 compatible screwholes and tongues on bottom
• A cover to hold the plunger in

Print in ABS (PLA gets soft at too low a temperature) and install in place of the original filament drive. Re-use the motor/drive gear/bearing combo, the M5 thumbscrew, hex nut, and Delrin plunger from the old filament drive (or get new ones). The whole extruder is way easier to assemble if you screw in the motor last.