First layer height - redo after every print
So we got a Prusa i3 MK2S kit a few weeks ago and it printed like a champ for close to 50 hours, but now there is something seriously wrong with the Z axis. We noticed that we hadn't tightened the metal frame quite hard enough to the threaded rods, so we undid the nuts, pushed the metal frame all the way in and tightened it down.
Next I reran self-test, XYZ calibration and fixed the first layer height (-0.360 was the number, this will be relevant later). I printed a bunch of simple spacers, everything went smoothly so I powered the printer off and left for the day.
I come back this morning, try to do a print, and the Z axis is WAY off. I had to put the Z adjust to around -0.500 to even get close to a decent first layer.
Since the beginning of the print was now ruined, I go to stop it and just start the print again, thinking this time all will be well, but no, this time I have to adjust it to -0.850 to get to where I was just 3 minutes ago!
What could be causing this? This is driving me nuts. I cannot think of a mechanical fault that could cause this, I'm very tempted to start blaming the firmware at this point...
Re: First layer height - redo after every print
Did you print the v2calibration.gcode after calibrating XYZ? The printer doesn't save Z-adjustment value, unless you print that. It took me a few tries to realize this myself.
Re: First layer height - redo after every print
!!! THANK YOU.
It all makes sense now. So there's some command in the gcode to save the values then?
Is this information available in the manual? If not it should be, if it is then I should probably learn to RTFM.
E: So how does the live adjustment work in subsequent prints then? Is it just not saved also then? Or does it behave like this only right after XYZ calibration?
Re: First layer height - redo after every print
Only after XYZ-calibration, as far as I know. At least that's how it works for me. And no, I didn't see any mention in the manual about this. I thought I could just skip printing the v2calibration and go straight to adjusting live-Z with regular prints, but I stumbled upon exactly the same issue as you.
Re: First layer height - redo after every print
You might be suffering from a not uncommon problem, see http://shop.prusa3d.com/forum/prusa-i3-kit-building-calibrating-first-print-main-f6/live-z-adjust-constantly-decreasing-t2118.html
Not sure if it has been explained solved meanwhile, I'm not following the forum much at the moment.
Re: First layer height - redo after every print
There is another potential Gotcha...
it seems that the PINDA Probe may be a little temperature sensitive,
and if you leave it close to the heatbed whilst heating for the next print, it will sense at a slightly different level and give the appearance of the liveZ value changing... and if you start readjusting the liveZ value, when you finish a taller model, the next time you print the PINDA will be cooler, it will sense at a slightly different level and again make it look like the LiveZ setting has changed...
what I do, is lift the extruder to at least 100mm, above the bed before heating up for the next job... and that way I don't have to fiddle with the LivZ adjustment between prints.
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
Re: First layer height - redo after every print
Thanks for all the replies.
The issue was of course not running the V2Calibration.gcode, once I did that the Z values started behaving as expected and everything seems to be working more or less as before now, with the addition of a slightly damaged PEI sheet due to the frame slippage.
On top of that I did notice an inconsistent first layer after switching from PLA to PETG (bed temp from 55 to 90), and this was mostly fixed by modifying the start and stop gcode to lift the Z axis to 120 to minimize the heating of the inductive probe as suggested in the linked threads.