Dual y-motor homing

Did someone of you already played with the “dual motor homing” option provided by grbl?
I just came across this release post and noticed the existence of this option.
Now I wonder why the Sienci-kit just comprises one homing switch for y direction as it seems that this “must have” is easy to install ( … and came already up in Aug. 2019).


To use the auto-squaring, the cpu_map is altered so that the Y axis would be controlled by two, independently acting drivers. You would need a different controller .

I think you’re better off just making the axes square or holding the gantry against the Y-plates or spacer blocks on power-up.

Hm what do you mean with different controller? It is designed for the arduino we’re owning and the board has 4 drivers (each y-motor has its own driver!)?

I am aware that the pcb layout would need some modification (cut throug the conductor paths for step and direction going to the second y-motor and to manually wire these to the D13/A4 pin).
Cooling and spindle direction are in general unused in the LM setup. But I think there is no need for a new controller/driver board … or what am I missing? :thinking:

So before doing this, I was interested if someone already tried this or played around with this, e.g. the Sienci team?

Btw I actually do not have any limit switches installed, but whats the point to install them and then not to use the soft limits because you need running into the limits for squaring? Or set up soft limits and then run the squaring by turning both y-leads by hand?

However, as it seems that no one actually played with this option, I will maybe look further into it over the christmas hollidays.

Thanks so far.

Nothing. Sounds like you get it.
I’m not sure I agree on the essential nature of the feature. I believe it was added for the MPCNC crowd… Those machines have a bit of slop.

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I am building my own CNC router, I’ve built 2 others but now I’m downsizing to roughly 36" x 50". I want to use GRBL based software and would like to also use auto gantry squaring. If you don’t mind me asking. Are you using an Arduino with a CNC shield??

I have a LM V1 with the corresponding controller which is based on an Arduino, and also an additional arduino with an older (dont know exactly, maybe a v3) cnc-shield. My plan was to understand wiring and configuration using the cnc-shield and than to adopt the setup to the LM controller… Unfortunately, I haven’t had that much time to really dig into this topic, some disease and other stuff came up.