Printer Lost Z Calibration and Cannot Calibrate Again
I've had the Prusa i3 MK3 for a few months now, and have done many successful prints with no issues or problems to speak of. Initial assembly and calibration went smoothly, and I was able to jump right in to printing my own models.
I started a print yesterday afternoon, checked on it after a few hours, saw that it was doing well, and went to sleep. By the time I checked the print this morning, the print had finished perfectly but I noticed the Z-axis was quite a bit higher than the print, more so than the normal amount it backs off after finishing a print. Upon trying to start a new print, the brief Z-Axis calibration step failed, the extruder was about 25mm above the bed at its lowest point. Trying to move the axis manually, the printer thought that 0.00 on the Z axis was the same about 25mm above the bed, even though it had just successfully completed a print and hadn't been turned off yet.
I tried running the calibration wizard again, which was successful up until the Z-axis calibration step where it brought the axis up to the top as normal, leveled it, but when it tries to bring the axis down (after the prompt to place a piece of paper on the bed) it only goes about 10mm before stopping and giving an error message: "Calibration failed! Check the axes and run again." I have restarted the printer and retried this multiple times. The exact phase that it is failing at is "Searching bed calibration point 1 of 4" After a series of restarts and beginning the calibration wizard from the beginning, I now have the same issue except the Z-axis travels most of the way down towards the bed before failing in the same manner.
To try and fix this, I have updated and flashed the printer to the newest firmware (3.3.1 as of today) which made no difference. I can still easily spin the Z-axis by hand while the printer is powered off, which would imply that it is not a mechanical issue preventing the axis from moving. If I drive the Z axis to the bottom by hand, and then run the Calibration Wizard, the printer can move the Z-axis all the way to the top normally, and knows to turn off the motors after it has been leveled.
I have tried googling this and all of the solutions found have not worked, any advice would be appreciated.
Re: Printer Lost Z Calibration and Cannot Calibrate Again
its pretty sensitive during the axes check, you can absolutely fail an axis due to an obstruction that you didn't feel by hand.
for z, i suspect the trap nuts my be too tight.
Re: Printer Lost Z Calibration and Cannot Calibrate Again
Thanks for the suggestion, I have tried both tightening and loosening the trapezoidal nuts but it seems to make no difference. I am confused because the printer worked perfectly through the most recent print and then simply sat idle for a few hours overnight and now has developed this issue.
Re: Printer Lost Z Calibration and Cannot Calibrate Again
In case anyone stumbles on this issue later, I found and solved this problem.
Turned out to be faulty wiring of the PINDA probe, but not in the locations most people encountered it. I had two bad spots just about halfway along the length of the wire, in the middle of the bend in the cable bundle. After cutting out and replacing the bad section of wire, I opened it up and found that both the white and brown wires had completely separated and were not conducting across themselves.