Lowrider V3, BTT SKR 1.3 with Klipper. Dropping Z

on my L2 I can get a drop if there´s to much pressure on the Z axis.
Maybe some pictures of the build can get you started to troubleshoot?

There is video. Everything works. But then it starts to drop. More often

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The first thing I would check is the grub screws holding the coupler to the motor shaft and the leadscrew.

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Thank you. Checked. Its normaly tighten up :slightly_smiling_face:

Curious what torque rating is for the stepper motors, able to share pic showing their label? Seen previous thread where steppers with lower rating struggle. To fix, not sure if they switched to (higher torque) stepper and driver specs matching v1e shop, and/or switched to 1 start leadscrews (requiring less stepper torque).

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Looks like x stepper is usongshine # 17HS8401S 48mm Nema 17 Stepper Motor, same ones used on z axis?

v1e shop sent me tmc2209 and steppers with torque mentioned here Nema17 torque question - #6 by aaronse

You are absolutely right.
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I put a huge vise on mine and it was still able to lift it. The Z should be very over powered.

So, other culprits:

  • vref. If it is too high, the drivers can overheat and shut down. The motors need to stay under 50C or so. The drivers will completely shut down if they get too hot. For 30s or so. If it is too low, then the motors will skip. The skipping sounds like crunching gears, but it is not mechanical.
  • intermittent wiring issues. These are a real pain to find and solve. But if something is loose, then the connector can work sometimes and not others. To make things worse, an arc over a small gap can make it look like it works, and the connector can heat up, which changes the connection reliability even more.
  • Wired in parallel instead of series or independent. A picture of your wiring may help us figure that out.
  • Too much friction. If there is a lot of friction, then theogors have more difficulty raising or lowering the gantry. But the force is greater when raising (because of gravity). Lube your screws. The gantry should fall on its own when you disable the motors.
  • Disabled motors. As long as the motors are enabled, they should hold up the gantry. But if they are disabled due to inactivity, then they may fall. The default Marlin has something like 20mins of idle time. The klipper, IDK
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what about the grub screws? Are they tight? maybe simply slipping?

OOPS, see that it was already asked. Sorry!

Huge wise? WOW.

-Vref. I tried Vref from 0,7v to 1.0V. So i think, its ok. But it´s behave like it´s overheating.
.Wiring is really pain in a**. I tried, but it seems ok. Maybe premade connector isn´t ok.
-I have 5 drivers. For every driver. For dual end stop, auto squaring.
-Theogors have a little friction, but i can rise axis by me twisting leadscrew. Leadscrew is lubed by lubricant for bearings and screws.

  • Searching for it from first time. But it falls only on one stepper. And during JOB :-/

Is it worth ruling out whether grub screws are the issue by using a Sharpie or Paint Marker where the leadscrew and coupler connect. Ideally you’d mark between stepper shaft and coupler as well, but that’s harder to reach and inspect. Maybe stepper shaft to coupler connection is less likely failure point than leadscrew connection anyway?

Feeble red line in the pic below is what I’m suggesting:

Thank you. But i am trying to figure out, why it falls randomly, but (in my opinion) with more tests, short gap between drops. No, why its falling permanently

So the driver shuts down for more than a few seconds and that leadscrew is just loose? Then you need to cool the drivers, or maybe replace one of them. I would start with 0.7V.

The other thing that could be happening is that it is still a wiring issue, and the connector heats up, and causes an open connection, which then acts like an overheated driver until the connectors cool down enough to close up again.

Yes. I cant hold hand on it. My optimal value was 0.7V. Replaced 3 of them on this port.
So, you think, there can by some small short circuit or something like cold connection? Because of it big resistance and overheating? mmmm Seems legit

Please be specific. Which thing is ‘it’?

I am sorry. Can´t hold hand on aluminium piece of passive cooling of DRV8825 Driver.

Are the steppers getting warm?

Can you point a fan at the drivers? A 12V fan can be wired straight to the PSU.

I am not sure about steppers. I can install fan. Do you think, is it enough?

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I would install a fan and bring the vref back to 0.7V. we have ran a lot with that config and drv8825s. That should be solid.

OK, any suggestion how big or efficient fan should be? Thanks a lot