Z Offset Changes?
Sometimes my Prusa i3 MK3s will print just fine, then other times the Z check at the begging of the print will be very cleary striking the build plate but still pass, then start printing while dragging the nozzle along the plate. Every time this happens I go through recalibrating XYZ, adjusting the pinda probe until it passes. I am about 90% positive that me adjusting the p[robe has absolutely nothing to do with causing the machine to pass or fail the XYZ calibration because it honestly just seems like it takes about 5 tries and then it will pass. Once passing the XYZ calibration it will work fine for about 3 prints then start acting up again. I've gone through this process at least 3 times now.
Any ideas?
RE: Z Offset Changes?
Check if pinda probe is not loose.
Check all your hardware if bolts are loose, every few months you should do this.
Do maintenance, put oil on the rods, clean it before the oil, check belts , etc.
Without oil i had the z go to the top and it was then not level, after oil it worked again.
RE: Z Offset Changes?
Striking the build plate should never happen. If it is, your PINDA is too high.
The PINDA is temperature sensitive: so on cold days it may work fine, on hot days it may cal differently. Some of us use the PINDA temp sensor to control the cal process. It adds time to a print, but yields a more reliable layer 1.
Adding M860 S40 to the custom gcode allows the PINDA to warm to 40c before running the mesh level... and leads to a very consistent layer 1.
; soak PINDA then level
G0 X50 Y50 Z1 F3000; this is a good PINDA heating position
M860 S40 ; wait until PINDA is >= 40C
G80 N7 R5; mesh bed leveling