Opinions needed for geared extrusion steppers. Please.

I want to use a geared stepper for my extrusion assembly. There are many planetary gear boxes for nema 17s. I was thinking about getting a 5:1 gearbox with a smaller stepper than what I already have, that being 84oz steppers.

The smaller stepper with the gearbox has a lot more holding torque etc, so im not to worried about that. What i am worried about is that maybe the geared stepped wont be quick enough during faster prints? I kind of think it will be ok, but it would be nice to hear it from someone else.

Also, a backlash tolerance of <=1°.... What do you think about that? Would that pose as a big problem? Im not sure because im thinking that each stepper step is 1.8° and each geared step is about 0.35°... So about 1° seems like a lot. What do you think? Will it be fine?

IMO, 3:1 is about the ideal gear ratio for an extruder for normal 1.75mm filaments. I used a 5:1 geared extruder for a while and found it too powerful, because when the nozzle was temporarily obstructed the extruder chewed up the filament instead of just skipping a few steps. If I reduced the current to reduce the torque, then I also had to reduce extruder acceleration because the reduced torque couldn't handle the rotor inertia. The solution would have been to use a shorter motor with less torque at rated current but also less rotor inertia.

So I think a short stepper motor with a 5:1 gearbox would be satisfactory.

The backlash will mean that you need a little more retraction to compensate, and you will probably hear a click on each retraction.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I was looking for a 3:1 and the only thing I found was 3EDs extruder. It looks nice, but I dont know. I see many people printing their own gears but in a few videos i saw, they was very noisy. Ill try the 5:1 with the small stepper. Thanks.

I saw your disclosure... I bought the Duet Wifi and the Panel Due with the 7" touchscreen. Amazing cool looking! Cant wait to fire them up!!!

The 3:1-ish extruders I have been using are the spring-loaded version of the Ormerod extruder, with printed herringbone gears. See [www.thingiverse.com] and [www.thingiverse.com] for the printed parts, and [reprappro.com] for the original design on which it is based. I changed to a Titan on one of my printers, not because there was anything wrong with the other design but because I wanted to try it out.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].