100:1 Geared nema 17 wont turn

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:

[www.omc-stepperonline.com]

Any ideas?

Edited 1 time(s). Last edit at 09/24/2014 09:34AM by gmh39.

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If the motor its self turns, it's definitely not an electronics problem.

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Yea I know. Just thought I should put what board Im using in case it might be a factor.

Anyway, the gear box should be able to be turned by hand, right? Or am I getting my gear ratios backwards?

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If you try to turn the gearbox backwards, then ofc you get the gear ratio backwards. If that friction would make it able to turn by hand or not, dunno, but at 1:100 probably not. Try moving it the normal direction, forward way, at 100:1 and that way should turn.

I have had two cases of stuck gear boxes, in both cases some teeth parts splintered and got stuck in the other teeths and froze the whole assembly. I guess thats a common fail mode. If it is *really* stuck you might need to dismante and clean it. But probably that is not the case.

Hi gmh39,

Please confirm if the the gearbox shaft really not run?
Because the gear ratio 100:1 is very big, when stepper motor's shaft run at low speed, the gearbox shaft might can not see it move, seems like static.
For example, stepper motor run at 100rpm, the gearbox will only run 1rpm.
Please try to accelerate the speed, and see what's result?

Got it working. Thanks guys. I had to up the steps/mm a whole lot to get any sort of movement.

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