Moving single z motor on multiple z motor setup

[curti]

I have a core xy machine with 4 belt driven z motors connected to the gantry for gantry leveling to the fixed bed .
(Google voron 2 for pics of the setup)

The nature of this setup is that when the machine powers down the gantry sags on the half with the xy motors (mounted to the gantry) due to it being the heavier side.

That wouldn't be an issue thanks to the magic of automatic gantry leveling, but it sags just enough that when I am probing the bed on the high side, the low side hits the mechanical limit of travel and "crashes".

Here is the question. Is there any m or g code that I can put into my settings (say bed.g ) that would enable me to do a relative move of a few mm on only 2 of the 4 z motors, lifting up the heavy side enough to continue the leveling process uninhibited?

There are mechanical solutions to my problem, but a simple software tweak would be the easiest.

Thanks in advance for the help.

[dc42]

You could use M584 in config.g to define 2 of the motors as belonging to the U axis as well as to Z, but use P3 on that command to hide the U axis. To move just those motors, send M584 P4 to make the U axis visible, command the U movement, then use M584 P3 to hide the U axis again.

[curti]

Awesome, that sounds like exactly what I need. When I get home this evening I'll give it a go.