Turn one of the three Z screws (steppers)

vistalert

Hi all,

What code can I execute to turn one of the Z screws in isolation of the other two.

I see this is the foundation of the true-bed-levelling.

I'm trying to get to a position where I can validate my bed frame is level at rest, which in my case means resting on top of the three couplers on the Z steppers at the bottom of the lead screws.

Thanks,
Chris

jay_s_uk

The best thing to do would be map the motors as individual axis and move them independently.
Once they are where you want them, you can map them back as all Z axis

Veti

have you read
https://duet3d.dozuki.com/Wiki/Bed_levelling_using_multiple_independent_Z_motors?

vistalert

@Veti yep, thanks, but it doesn't explain what command might turn only one stepper motor. Maybe this is just my curiosity to know

I am going to be following along with that article to get individual end stops setup - I just received three optical end stops today. I guess in this context, there would be a tuning process to get the head close to the lead screw, make it touch the bed, and set the end stop for that position? is that correct?

Thanks
C

vistalert

@jay_s_uk I see your logic here, but to re-map I'd have to modify config.g which causes a reboot, which causes my bed to drop (it's the size and weight of a truck).

I'm waiting for leadscrews with a shallower incline (not sure how to describe that), which I hope will hold the bed when powered off. Else, I can't every recover from a power loss.

jay_s_uk

@vistalert you can remap outside of the config.
Most options can be changed on the fly and remapping axis is one of them.
Remapping was the way independent axis would have to be homed before RRF2

vistalert

@jay_s_uk ah I see - so just execute that gcode in the console. Thanks! #stillanoob

Veti

the idea is that the duet does this automatically for you.
there is no need to move one motor on its own.

fcwilt

@vistalert said in Turn one of the three Z screws (steppers):

Hi all,

What code can I execute to turn one of the Z screws in isolation of the other two.

I see this is the foundation of the true-bed-levelling.

I'm trying to get to a position where I can validate my bed frame is level at rest, which in my case means resting on top of the three couplers on the Z steppers at the bottom of the lead screws.

Thanks,
Chris

If you install end stop sensors for each of the three steppers then the Duet firmware will level the bed for you - first using the end stop sensors, then using the Z probe.

Of course you have to have a Z probe and setup bed.g correct for use with G32.

Frederick

vistalert

Thanks everybody. I should explain my printer is built and configured etc. and everything functions.

I generally want to learn how to build with more accuracy, as opposed to relying on smarts to compensate for what could be something that's misaligned, and potentially wearing over time.

It seems logical if I can tweak the Z motors individually, I could level the bed to the nozzle, determine how many steps it took to get there from the bottom (parked position as I call it, resting on the couplers) and then determine if my components are installed to some higher-degree of accuracy by deducing the bed is not level, therefore the stepper motor bracket is deflecting...therefore the quality of the bracket should be improved...not compensated for.

...it sounds like the axis mapping suggestion is the answer.

Thanks
C

Veti

@vistalert

yes, but you did not account for stepper misalignment when they are powered off.
its very likely that the steppers are out of sync afterwards.

Phaedrux

@vistalert said in Turn one of the three Z screws (steppers):

as opposed to relying on smarts to compensate for what could be something that's misaligned

If you can't make it perfect, make it adjustable. If you can't make it the same every time by hand, make it automated.