Are you supposed to see z-axis changes mid print with ABL?

I've recently got ABL working with my Anet A8, and the prints are coming out great, but when I'm doing prints on pronterface I don't notice the z-axis height changing as it goes around the bed, shouldn't I see this value fluctuate by a couple hundredths if my bed is about that far out of alignment in any given spots? I thought maybe the value just doesn't update but I also don't see my z stepper motors moving as it prints across different parts of the bed. I've got G29 enabled on my starting g-code, is there something else I'm missing? If I can't observe any changes in the z-axis during the printing of a given layer, is it really bed-leveling at all? The prints are coming out good so surely something must be happening I imagine

my interpretation would be no. What ABL does is to level the bed so Z=5.000 at one point is Z=5.000 at any other point. Therefore, Z does not change when Z is actually moving. Beside that, Marlin gives out position data for G28, but not other commands, so Pronterface has no way of knowing that Z is moving to level the bed.

Edited 1 time(s). Last edit at 05/29/2020 09:08AM by ruggb.

ABL is controlled by the firmware so no you will not see any minor fluctuations in the pronteface Z value,but you should see the Z motor
move slightly as the X Y traverse the bed, but only for the 1st few layers as ABL has a fade value where it determines the print is levelled.

Maybe your bed is already level? Otherwise, you should see your Z steppers also turning as the nozzle moves in the X and/or Y direction, to compensate for the out-of-levelness of the bed.

As others have said, the levelling is done by the firmware, so Pronterface will send the nozzle to a point in 3D space, but the firmware will send it to somewhere else, depending on the slope of the bed. "Somewhere else" is calculated by doing a 3D rotation to match the plane of the bed. (So bed levelling isn't that at all; instead it's model-tipping).

When my bed was very unlevel (greater than 1mm from side to side) I could see the Z steppers move to compensate. After I got the bed dialed in, there was little to no noticeable motion.