100:1 Geared nema 17 wont turn

[Eudora]

I'm designing an extruder with a 100:1 NEMA 17 motor. When I went to test the motor yesterday it it wouldn't turn

I took the gear box off and the motor itself would turn, but the gearbox wouldnt. When I dismantled the gearbox, I didn't find anything unusual, so I'm kinda stumped why it won't turn.

I'm using a RAMPS board with DRV8825 drivers. Here's the motor I'm using:

https://www.oyostepper.com/goods-304-Nema-17-Stepper-Motor-Bipolar-L%3D48mm-w-Gear-Ratio-100-1-Planetary-Gearbox.html

Any ideas?

[Ctec]

The stepper motors have a torque/speed characteristic like this one

where red is for high voltage, blue for mid voltage, green for low voltage.

Assuming you are using your one at mid, you can see that the nominal torque is decreasing dramatically after a certain speed.

You are using a 1:100 gearbox, so assuming you want 50 rpm in output, you must run the stepper at 50x100=5000rpm. That value is usually too high, you should be a lot on right of the graphic, so the actual torque that the motor can provide (and a NEMA 17 is a very little motor) should be not enough to make the gearbox rotating.

Please add more information about the application, or check better that the motor is big enough to provide the torque you need (we are speaking of no load application, imagine if you have a real load...)