1.75mm filaments are slowly becoming mainstream, due to the design choices of the commercial 3D printer manufacturers. That has recently caused me some long waiting times for 3mm filament, while 1.75mm rolls were stacked high…
Enter a reworked version of the ReprapPro mini extruder.
It is modified to use a 20mm M4 bolt in stead of the M3, with more readily available 624 bearings, and a new 10mm drive gear. The reason for the changes were that my 0.4mm nozzle started to block, but not enough to look blocked. This tripped up my airtripper, causing filament slippages, warps etc. I needed something that could cope with the pressure.
The drive gear is 10mm OD, 8mm long and tapped M4 in the center, with M6 hobbed wormgear on the one side of the barrel. I just edged off the two sides for it not to interfere with the sides of the 624 bearings.
This extruder managed to print past the blockage for an entire roll of filament. Of course, when I cleaned the nozzle, everything worked infinitely better, but in the end, I gained a foolproof 1.75mm extruder.
The stl files are added into the Morgan repository, but you can get the extruder sources here: