Ridiculously Inconsistent Z Axis
When I've cooled off, I'll get back with pictures, but I've been having a very frustrating problem with the I3 Mk2; After making 2 beautiful prints after a new hot end assembly replacement (This printer has spent more time broken then operational now), I went to print something this morning, and was having problems with bed adhesion. Today was the first print with a heated enclosure, and I was running the printer at an ambient air temp of 34°c, a bed temp of 60°c, and extruder temp of 210°c with PLA (Recommended 200-220°c temp). After three attempts with just using Isapropal Alcohol to clean the bed (usually enough with PLA), the fourth time I used glue stick, and it looked like the golden ticket, so I let it go for about 2 hours, and came back to a catastrophic print failure, and a huge glob of PLA attached to my hotend.
I cleaned the hot-end, and tried to run it again, and noticed the filament was not compressing well to the bed. I last adjusted my Live-Z for prints that had already came out stellar, currently at -0.500mm. I figured something moved when the glob happened. So first I recalibrated the XYZ, then I used the single-layer rectangle trick to adjust my Live-Z again, and got it perfect, but at a whopping -1.400mm. That seems like quite the offset, and I don't think thermo-interference with the probe can explain that. Either way, like I said, it was perfect, so I started the real print, and the nozzle was way too high again. I just can't seem to win. The calibrations and subsequent prints only had an ambient air temperature difference of maybe 3-5°c.
I need to take my mind off this before the Prusa ends up in the trash. Hopefully someone else has had this problem before
Re: Ridiculously Inconsistent Z Axis
That certainly is not a problem of a well built and maintained Prusa-Printer.
First, PLA sticks to the PEI sheet like hell.
Usually just some water with VERY few solvent in a spray bottle is well enough to clean the bed while preheating.
As far as I understand there happens kind of a Z-shift which most likely may caused by some mechanical reason.
Maybe there came something loose in the nozzle changing process...
My MK2S now is 9 months old and pretty well works like intended.
Some pictures of the 1st layer and some test parts may be of help to determine the reason for the problems.
Throwing this one in the trash and buying an other one most certainly will not solve the underlying problem...
Re: Ridiculously Inconsistent Z Axis
Most likely your PINDA sensor is moving/getting bumped/vibrating/twisting somehow during the print, and this is causing the inconsistencies. I have been having the same issue. Had to tighten the PINDA down better so it couldn't move.