Easy, and well worth the effort…
The Mini z-axis motors are not timed to each other, nor checked. Both stepper motors receive the same pulse train for moves in either direction. Sometimes, a pulse is dropped by one or the other motor, and eventually after a gazillion pulses, you’re off by a few. Or a few hundred. But that’s not really enough you can tell with your eye usually.
This mis-synching will cause you to hear a strange click of various frequencies from your machine while printing. This is because the system creates a virtual plane, tilted side to side, based on where it sees the four corner washers. If it sees the right side low or high it compensates for that and creates a new plane. Good if it’s close. Not so good if it’s off quite a bit. And it’s easy to fix.
I’m sure it can be off in the Y-axis direction, but that would require shims or stuff. My Y axis is close enough not to worry. Yet.
I used Cura, the default homing. Just let your machine do the homing sequence normally, but watch the control panel display. When it’s done, you will see something like:
The four sequential < Bed x: numbers are for each corner as it zeroes. You want the second and third to match the first and fourth, or as close as they can.
To fix it, you just turn the right hand leadscrew with the machine powered off completely. Do 1/8 turn and rehome it and see what effect it has. Take out the filament to make it easier if you wish. Turning it ccw from above has the effect of making it touch sooner, use this for numbers that are larger on #2 and #3 positions. I think I did a couple 1/8 turns to get mine where it was pretty close.
The left hand lead screw is closely coupled to the home switch, so it won’t have much effect, if any.
No more ticka-ticka-ticka when printing in the X direction! Maybe cooler running Z motors? Maybe better quality prints? Give it a shot and let me know how bad yours was.
If this has been discussed before, I apologize. I searched.