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Z Axis Resistance?

My Z Axis is not responding consistently. It usually goes down correctly, but then won’t go up as much as it’s supposed to, resulting in predictable problems. It looks like it’s meeting some resistance, but there’s nothing that I’ve seen that would cause resistance. It also doesn’t always happen at the some point of travel.
I’ve attached a video of me jogging the stepper up and down. Yes, I know I kept jogging it up after it reached the top of its travel. I was trying to jog the motor on my computer while aiming my phone at it. I do not multitask well.

it looks like stepper motor internal lock caused by max speed or acceleration being set too high… What are your grbl settings?

you can read them at the bottom of machine inspector:

Thank you!
If I’m reading this correctly, and there’s a good chance that I’m not, then the Z stepper’s max rate and acceleration are both lower than those of the X and Y steppers.

$100=40.000 (x, step/mm)
$101=40.000 (y, step/mm)
$102=320.000 (z, step/mm)
$110=8000.000 (x max rate, mm/min)
$111=8000.000 (y max rate, mm/min)
$112=500.000 (z max rate, mm/min)
$120=500.000 (x accel, mm/sec^2)
$121=500.000 (y accel, mm/sec^2)
$122=50.000 (z accel, mm/sec^2)
$130=750.000 (x max travel, mm)
$131=750.000 (y max travel, mm)
$132=100.000 (z max travel, mm)

Check the pulley set screw. The pulley may be slipping on the motor shaft.

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sorry I’m not intimately familiar with those older models… IF that is set the same as the version that uses the Dewalt (pre Nov 2021) then the $102 should be 160 (see video at the end on how to verify the correct setting and to manually calibrate it)

but are the z movements equal to those commanded? IF not then this setting might be wrong… and IF it’s higher than it’s supposed to be it will cause the Z to spin faster than its supposed to and thus could be the issue…

I like Neil’s approach here, but in watching on my PC monitor i can see that the motor shaft is also stopping when its locking up, so it’s not the set screw issue as that wouldn’t lock up the motor… now a loose wire might cause intermittent issues like this as well. :man_shrugging:

Here’s the process to see if calibration (while it is not locking up) is correct: Just perform this measurement of actual vs commanded movement for that Z axis to see if it’s actually moving what you’re telling it to move…

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I didn’t check the stepper, but thanks for sharing that. It’ll be good to know how to do it.

I think I found the culprit. I took the belt off of the stepper and then it seemed to work without a problem. If I turned the threaded rod for the Z axis by hand, I could feel intermittent resistance. The rod looks fine. I don’t know if it comes through on this video, but there’s a defect in it.

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