RE: Z calibration
Mr Cook,
Have you tried a more rigorous Z calibration using a test print? I'm attaching one similar to the one used in my photo above if you would like to try it. The one I'm attaching is one layer. Slice it at .2mm layer thickness. I suggest all other default slicer parameters unless there is a very specific reason to change them.
This will let you know for sure if the Z calibration is dialed in close or is wonky. In particular it lets you see any issues across the bed and then you can tweak the front/rear and left/right fudge factors if you need a further correction.
For the smooth sheets, I 'tune' the Z for the best looking 'squish', as in the diagram immediately below.
You should be able to look at the top of the squares and easily get an idea if the 'squish' is in the ballpark. It looks to me like your photo above might have the Z set too high, as there is 'daylight' clearly visible between the strokes.
For the textured sheet I've been employing a slightly different tack, as I've been tuning the Z to the point that the 'brush strokes' just disappear into the textured pattern on the bottom of the test print.
I also have to 'agree to disagree' with the notion that different filaments require different Z calibrations. I've found that once the Z is dialed in for a particular sheet, it will reliably print across the spectrum of PLA-PETg-ABS and across all major brands without further tweaking. The only time I've found that a different Z calibration is needed is when changing sheets.
I hope this helps. The Prusa machine is definitely not 'first time every time', but 'first time most of the time' is quite attainable.
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that z offset seems like half a millimeter to high. if the filament is not properly squished to the bed, it cant stick to it and your parts will detach.
for dialling the z offset, it is best print something .2mm tall so it is only one layer like jsw wrote. you can create such forms in prusaslicer itself, just right-click in the right window where your parts would be listed, add - slab/cube-whatever. click it and change its dimensions to .2mm height.
after printing, this foil should also be .2mm thick if your z is adjusted properly. otherwise you can adjust your offset by how much your printed foil is off during the next test.
z offset will be different with different sheets since their thickness varies. use the different sheet slots in setting-hardware setup-steel sheets in the printer's interface to save and select them when needed.