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PDBeal
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dc42
For the extruder, I recommend using a gear ratio of between 3:1 and 5:1 with 1.75mm filament, and a stepper motor with 20 to 30 Ncm holding torque at full current, with a current rating in the range 1.2 to 1.7A (or 1.2 to 2.0A if using the Duet WiFi). I use JK42HS34-1334 motors and an extruder gear ratio of 34:11.
I'm curious, why the suggestion in geared extruder? Just for more torque at lower current with smaller motors? Or was there some other reason I'm not seeing?
Because to be sure of getting enough extrusion force with a non-geared extruder, you need a long, heavy Nema 17 motor run close to its rated current. It's not just the absence of gearing, it's also the fact that the hobbed drive element has to be larger, because it has to fit over a 5mm motor shaft, whereas the hobbed insert on a geared extruder typically fits over an M3 screw.