This is some weird thing I designed to convert an Ender 3 to geared direct drive extrusion with mounts for an 18mm inductive sensor and a 50mm blower fan for part cooling.
The gear ratio is 1:4 (16/64 teeth) and uses herringbone gears with a module of 1.11mm. You'll have to either quadruple your steps per unit in firmware or up your extrusion multiplier to 400%.
The motor, drive gear, tension spring and filament roller can be used from your existing extruder or purchased separately. It is designed to fit a knock off V6 hot end but should fit the genuine one in theory, you can either use the stock V6 cooling can or print the one included (requires a 40mm fan).
You will also require: 2 x 683ZZ bearings 1 x 608ZZ bearing 1 x 50x50x15mm blower fan 18mm inductive sensor (remember to add a voltage divider) 4 x 40mm M3 screws (can be longer) to mount the hot end and sensor A pack of assorted M3 screws and nuts (too lazy to list each length) 40mm fan for hot end cooling An M5 bolt(35mm or longer) with a hex head and nut for the filament drive shaft A short M4 hex screw to tension the filament roller You will also need a small length of PTFE tube to bridge the gap between the filament drive gear and the hot end
I printed it at a 0.3mm layer height, 3 walls, 3 top and bottom layers with 25% infil. The gears should be printed at a 0.2mm layer height or lower and slowly as the teeth are quite intricate. Ensure your horizontal expansion is calibrated before printing as some parts have little to no tolerance for error.
You will need to extend the cable for your extruder motor as the stock one won't be long enough.
Also note that I have a clone of an Ender 3 and was used as reference for the design, this may or may not fit other clones or the genuine one so check first.