Z Calibration results in hotend touching heatbed and failing calibration
I've had my i3 MK3 for a while now and just finished rebuilding/upgrading to the MMU2s / MK3S. I upgraded to the latest firmware 3.8.0 as well.
When I go into the menu and calibration and choose the auto wizard or even just Z calibration, I end up with a failure. The X carriage moves to the top of the printer and clicks as it hits the top supports/end of Z travel as expected. As the extruder comes down to the heatbed (no plate installed per the wizard's request) the nozzle just touches the heatbed and I get a calibration failure. The Pinda probe light goes off, so it correctly detected the heatbed (moving it back up 1mm and the light comes on again). Looking at the Z height it says it is at 5mm. Sure enough, going down 1mm the heatbed deflects slightly as the extruder pushes into it. If I go up to 210mm it looks to be 5mm shy of hitting the Z suports/end of travel there now.
The pinda is correctly setup (zip tie thickness above the nozzle when nozzle just touches heatbed). If I manually move the Z axis to get the nozzle to just touch the heatbed, reset the printer then move it up to 210mm, it just kisses the Z stops. I haven't tried moving it down 210mm to verify it just touches the heatbed again, I figure the Z calibration is already doing that for me and failing.
I've rebuilt the printer a few times due to various issues and have run through the calibration process without issue, up until now. I've got to be missing something simple? Fwiw, the printed mk3s parts are direct from prusa. also, I was able to calibrate properly on an older firmware (3.7.2 or thereabouts) as I had problems with the mmu2 board and wanted to print parts while waiting for a fix on that, so reverted to the mk3 firmware with the mmu2 disconnected. The last oddity (don't think it matters) is I'm having loading problems with the mmu2, so I currently have the mmu2 bypassed by feeding filament directly to the extruder (not through mmu2) while keeping a piece of filament in the mmu2 to fake out the sensor.
RE: Z Calibration results in hotend touching heatbed and failing calibration
If during this process the nozzle makes contact, odds are high the PINDA-Nozzle height is too high; try lowering the PINDA so it is no more than 1.2 mm higher than the nozzle. The MK3S changes the geometry enough you're old stored MK3 settings will be wrong.
ps: a few have found doing an AutoHome seems to reset some things and somehow makes subsequent cals work...
pps: have you done a full FACTORY reset with Data Clear? That's mandatory with the S upgrade.
RE: Z Calibration results in hotend touching heatbed and failing calibration
@tim-m30
Thanks for the reply!
I forgot to mention that yes, I did reset all calibration data (whatever the option is in the menu, the live Z adjust was zeroed out as a double check).
I'l try an auto-home tonight. I was thinking the pinda might be wrong, but 5mm? Fwiw, just as the nozzle kisses the heatbed the pinda light goes off so I'd think it is adjusted right (the pei sheet being removed would account for the nozzle getting to heatbed as pinda detects).
RE: Z Calibration results in hotend touching heatbed and failing calibration
PINDA should turn off at least 1 mm before the nozzle contacts. Then Live-Z is used to reduce the height to 0.2 mm once cal'd.
RE: Z Calibration results in hotend touching heatbed and failing calibration
Heya - I've got the same issue, did you find a solution?
Fred
RE: Z Calibration results in hotend touching heatbed and failing calibration
I am going through the same issue for the past 5 days. I can't figure this out. Does anyone have a solution?
RE: Z Calibration results in hotend touching heatbed and failing calibration
Add me to this list! I just reassembled my extruder and somehow the PINDA got moved WAY too high. I used a zip tie to put it at the correct height but I fail Z calibration every time!
RE: Z Calibration results in hotend touching heatbed and failing calibration
So...many of us are having this issue, yet nobody reads this thread anymore or reports how they fixed the problem? I love my Prusa printers but am getting pretty frustrated lately, I haven't been able to print right in a long time. I was having general underextrusion issues, so used the MK3S+ upgrade as an excuse to rebuild the extruder and make sure everything was perfect there, and that just opened up new cans of worms. I'm in NinjaFlex hell, I used to have it down but recently the underextrusion (which is easy to address with hard filaments) became a nonstarter. After the MK3S+ upgrade, the design of the idler tension seemed to tighten up a bit, leaving almost no wiggle room between the screw falling out and the filament wrapping around the idler. To be sure, I replaced the nozzle, and entered nozzle overflow hell, the nozzle replacement process (as many complain about) is likely to get the nozzle-to-heatsink path messed up. Just did a teardown and rebuild and got that all resolved, did a few cold pulls to be sure, and tried the Z-axis cal---which failed exactly as per others in this thread. What the heck? I've had no issues with this before, nothing else changed. It literally deflects the heatbed in back, reported and error, and froze up in that position. I manually released it but it damaged my heat bed. There are a of of sensitive sloppy design issues in this otherwise beloved printer, and I seem to have joined the group that found this one.
What have the rest of you found to resolve this?
RE:
Ok, I thought I'd report back after trying some ideas from this thread. Frankly, I've been doing this for 3 years, built my MK3, upgraded from MK3 to MK3S to MK3S+ (plus got my new mini up and running)--first time I've heard there was a factory reset option, this never came up in the Prusa upgrade walkthroughs. So...I found this page and did everything--but first, I had an idea of what might really be wrong. After the nozzle replacement and subsequent extruder rebuild, I did the 1st layer calibration, but I did NOT check the PINDA alignment, I assumed it would still be good. BAD ASSUMPTION, the nozzle had moved, and now I realize that what matters most is the relative alignment between the two. So, I readjusted that, but was still having Z-calibration issues. So, onto the full reset procedure. After doing that, the setup wizard finished successfully, and the printer is currently 50% done with appears to be a lovely 3DBenchy. Honestly I'm not sure which of these two actions fixed the problem, possibly even both. FYI.