“first layer calibration” Z height changes "in real life" after a reboot
 
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HugoCraft
(@hugocraft)
New Member
“first layer calibration” Z height changes "in real life" after a reboot
  • I do the “first layer calibration” and I end up around -1.5mm with the correct layer height
  • I then print something that was sliced with prusa-slicer.  I then have to use the live Z adjust to change it around -1.8mm to get the same height as during the “first layer calibration” wizard.
  • If I don’t reboot the printer then I can print again without changing the live Z.  Don't reboot and I keep printing with no issues.
  • If I reboot the printer then go to print the same gcode again, then it starts printing 3-6mm way too high above the bed!  If I cancel the print job then start the same job again then it would usually be the correct height but that was before the recent firmware upgrade. 
  • With the most recent firmware upgrade, after a reboot then it prints 3-6mm too high but canceling the job and starting again doesn’t fix it so I have go through the  “first layer calibration” again to setting it around -1.5mm but during the first print I have to adjust it again to -1.8mm
  • I’m using the smooth sheet.  Also at my work/employer we have the Prusa I3 for years so I have a decent amount of 3d printer experience and once “first layer calibration” is set with the I3, we rarely have to touch it so it's a little frustrating the mini I have can’t keep the correct first layer height in real life saved.  Seeing it start at 3-6mm too high is sad to see.
  • I just sent a message to prusa support to see what they reply back with.
This topic was modified 3 years ago 2 times by HugoCraft
Posted : 16/02/2021 5:45 pm
ideastudios
(@ideastudios)
Eminent Member
RE: “first layer calibration” Z height changes "in real life" after a reboot

This post may actually be describing two different issues. There's no way that printing 3mm or 6mm above the bed is the same issue as the Live Z Offset issue (after all, the entire range of that is 0 to (-2) mm).

I actually had a similar issue to that (printing a huge way above the bed - 3 to 6mm) and it was very intermittent, but I did similarly notice that behavior changed after a reboot.

I personally adjusted the PIDNA probe (move the probe upward, away from the bed) such that my Live-Z was something like (-0.420). Since then, I have similar issues where I just printed to air.

Posted : 16/02/2021 9:25 pm
HugoCraft
(@hugocraft)
New Member
Topic starter answered:
RE: “first layer calibration” Z height changes "in real life" after a reboot

@technogeeky

The Z adjust number I'm already using is -1.8mm and the max is -2mm so if I move it any further up then I would be out of range

Posted : 16/02/2021 9:32 pm
ideastudios
(@ideastudios)
Eminent Member
RE: “first layer calibration” Z height changes "in real life" after a reboot
Posted by: @hugocraft

@technogeeky

The Z adjust number I'm already using is -1.8mm and the max is -2mm so if I move it any further up then I would be out of range

Likewise, I have to think about the logic for this every time, but...

If you move the PINDA sensor up, then the nozzle will be lower relative to the PINDA sensor. This means you will not need as much negative Z offset for the nozzle to lay down a proper first layer.

Posted : 16/02/2021 9:35 pm
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