Add Mechanical Gantry Calibration G34 for users that have dual Z on ender 3 4.2.2

I added z-axis to my ender 3 using a 4.2.2 board. I was wanting to make sure the axis was level but I don’t see G34 as an option for either the firmware builder or in the prebuilt builds.

Since you are using the original 4.2.2 board, you cannot use G34 as it doesnt control each Z stepper seperately, it just sends them the same signal so they move together.

Doesn’t need to have an additional driver as it is mechanical.

I need to look into this - as I also need to understand what safety requirements also need to be set.

I’d hate to enable it, but not have the right knobs to tweak and end up damaging peoples printers…

Sorry for the delay in this - but G34 Mechanical Gantry Calibration is now available in the Firmware Builder.

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So i just tried this feature on my skr mini e3 v3. while it goes up, it doesnt do a 9 point calibration. Am I missing something?

I’m not sure what you mean by this? How do you get 9 points on the Z axis?

What it should do is just raise Z until it hits the top of the frame. You probably want to fit some bumpers to the top to allow this.

I watched the video above, and at 26:23, it talks about after doing the test it will probe multiple points.

Also, in this teaching tech video with the G34, this one is different in the sense that it doesnt hit the top of the frame, but uses a BL touch, but in both cases after doing so it will do a multi-point verification.
Specifically talked about at 14:55:

I dont know why the video shows “unavailable”. Here is the title to seatch on youtube:
3 ways to add a dual Z axis - Including G34 auto Z levelling

I hope this helps with my explanation. I just installed a dual Z with my SKR mini e3

The video comes up as unavailable - but I think you’re talking about the side-to-side probing.

This only works if you have two independent Z stepper drivers. Neither the Creality v4.2.x boards or the SKR Mini E3 boards (any version) have two Z steppers.

When you only have one Z stepper driver - but drive two Z stepper motors, then you can only do mechanical method - ie smacking it against the top of the frame…

Yes, you are correct. I am sorry i dont know why the video isnt showing. The Creality series boards do not have the second stepper motor, but the SR mini e3 v3 board does have it (it was the main reason I purchased the board)

Unfortunately, the SKR Mini e3v3 only has 4 drivers and only one driver is for the z axis. It has 2 ports but they are controlled by the same driver so both ports for the z axis are not controlled independently. I would look into Mechanical Gantry Calibration and not software or look at getting another board that has 5 or more drivers.

you are 100% correct, I was mistaken! Thank you for pointing that out

I understand the Prusa has dual z with one driver. The z Motors are in parallel same as the add-on used by many Ender and others.

The way Prusa does it is to reduce the drive current, run motors up till they both stop because of sensorless homing on all axis. The z current is reset to normal after homing. They also use a constant but low z motor current to keep z alignment between prints. As long as power is on, z is energized and doesn’t lose position.

Is this doable for SKR mini e3v2 or others of similar with four tmc2209?