after some motion, one of the axis stop moving

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joram
Posts: 3
Joined: Tue May 14, 2019 2:23 am

after some motion, one of the axis stop moving

Post by joram » Tue May 14, 2019 2:42 am

Hey,

When starting a mill job, things run smoothly until one of the axis stops responding. The test job I'm running contains a spiral down to start, and one of the X or Y axis stops responding. if I stop the job, and operate the mill manually, the other motors lock appropriately as I try and move the one axis, but I need to power down and back up to have it controlled.

I'm operating with DRV8825 drivers, 2 nema17 steppers, a nema23 (to move the weight of the work), and controlled via cncJS.

I thought it may be the amperage provided by the PSU, but I bumped it from a 10A to 20A unit without any change in symptoms.
I thought it may be the calibration of the current limit on the DRV8825s, so I rechecked those, they're tuned properly.
Not sure what could be causing it at this point, any thoughts?

Thanks for your help in advance,
John

Bertus Kruger
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Re: after some motion, one of the axis stop moving

Post by Bertus Kruger » Wed May 15, 2019 7:22 pm

joram wrote:
Tue May 14, 2019 2:42 am
... one of the X or Y axis stops responding ...
Try and find the axis with the issue first. Then narrow down on the stepper driver.

Cloning an axis is better than running two steppers from one driver. But cloned axes need to be tuned
or one of the steppers could stall while the other drives ending in a misaligned axis.

joram
Posts: 3
Joined: Tue May 14, 2019 2:23 am

Re: after some motion, one of the axis stop moving

Post by joram » Wed May 15, 2019 10:39 pm

Hey Bertus,

Sorry I didn't make it clear, it consistently has a single axis stop responding, sometimes it's the X axis, and sometimes it's the Y axis.
It's a three axis machine, with a single driver per stepper for x/y/z, there is no cloned steppers in the mix.

I disconnected the steppers from the machine, and ran the same gcode again, just in case it was some mechanical resistance, but the same problem occurred.

It's good to know that cloning is the right way to go, if I change the structure in the future.

joram
Posts: 3
Joined: Tue May 14, 2019 2:23 am

Re: after some motion, one of the axis stop moving

Post by joram » Mon May 20, 2019 6:05 am

Solved: The stepper driver as overheating, and then had a safety cut-off. Since the initial motion was spiraling down, it meant that it could be the X or Y that failed.
I put heat sinks on them, then adjusted the potentiometers controlling the current limit again, and it now works smoothly :D

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