Z axis homing on maiden operation, is z probe required for series machine?

I’ve built my lowrider 2 with the series config as recommended by Ryan, ramps 1.4 hardware.
I have never used this machine for milling before, only doing the crown test.

Does this still need a z probe or does it use the current position when it’s on as it’s home?
It seems my machine wants to nose dive even though I have no endstops on it.

Additionally, one of the z steppers appears to skip at a certain point when moving larger distances, not sure if it’s the weight of the spindle on that side or not, or if I haven’t currently squared it (what’s the process for this without probes / endstops?)

When I choose the file to print. It sits on the screen below asking to attach z probe, hence my question. Then when I click the button again, it keeps trying to lower the z until I turn off the machine.

I’ve attached the gcode that I have generated from Fusion 360 (if this might be the problem), also attached screenshot of the toolpath.
My crown test worked fine, but I don’t recall that moving the Z at all (this was generated from estlcam).

AGW-v1.gcode (1.1 MB)

Here is a link to the video with the skipping https://youtu.be/qS0mfn7OMl8

Found the culprit in the postprocessor for the ‘nose-diving’!

That doesn’t rule out the skipping issue though, will try the cut again tomorrow to see if it skips mid cut.

image