Very Inconsistent Bed Z adjustment?
I've had a MK3S+ for a while and recently the printer suddenly started printing with the nozzle far above the printer bed (about 1.495mm or more). I re-ran the first time setup calibration, then set the Live Adjust Z value to -1.495 which worked for the center of the build plate. But the edges seemed to not be level with this value so I followed the bed level correction steps in this Prusa help article. This worked, and I was able to use the printer fine for a week or two, but then the same problem suddenly happened again.
When it happened again I tried the same troubleshooting steps as before but noticed that whatever adjustment/correction values were working for 1 print attempt, would no longer work on the next test print. I used a 30x30x0.2mm square created in Prusa Slicer as a test print, and found a Z adjustment value that seemed OK.
After that, I tried the bed level test print which failed miserably.
As another test, I used my custom center square print again and from the looks of it, my nozzle's Z level is much too high with no changes in settings.
All of these results came from exactly the same settings with no changes in between.
What else can I check to figure out what is going on here?
And a few extra details in case it matters: I'm using the silver Prusament PLA that came with my printer, which was removed from its vacuum seal the same day that these tests were run (haven't needed silver until now). I clean the bed with 99% alcohol before each test, and also wipe the nozzle tip clean before each test.
RE: Very Inconsistent Bed Z adjustment?
Did you check that the Prusa sensor is properly secured? I'd give the screw that holds it in its holder a turn.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: Very Inconsistent Bed Z adjustment?
I tried tightening the screw that holds the pinda sensor and that seems to have possibly made a small difference. After tightening, I re-ran the first time setup wizard and configured the Z adjustment again, and the Z height seems to be slightly more reliable even with bed level corrections set to zero.
However, I'm still having the same issue where each time I print the Z height needs to be slightly different. I've noticed that, for whatever reason, large prints (in X/Y dimensions) seem to cause the alignment to become worse. I can print my single-layer 30mm square in the center of the bed several times in a row with consistent results, but printing the Prusa bed level test will usually fail badly, even in the center region for that test. After the bed level test, my previously OK 30mm square ends up looking like the Z adjustment is wrong.