PrusaXL erroring out mid print  

PrusaXL erroring out mid print

Good day everyone,

Hoping someone can help.  I have a Prusa XL single nozzle.  I have made several successful prints on it (16 days of print time).  However, today, I have had two failures several hours into a print.

Failure 1:  The printer stopped moving (and appeared to freeze completely) mid print.  The screen was still responsive, and I was able to cancel the print.

Failure 2:  The printer started doing "air moves" mid print. (I don't know how to describe this, but the print head just started randomly walking all over the print bed, where the part was and where the part was not.  I tried pausing this one, and resuming it, but it resumed making random air movements at random speeds, and printing in the air.)

Prior to these two back to back failures, I had been able to complete multiple large parts successfully.  (My printer has a small elephant foot problem, but the layers up to the failure points are well within what I expect the printer to be doing.  It has been upgraded to firmware 5.1.2, and I was printing binary gcode from the USB stick.)

Any suggestions on where to troubleshoot?  Thanks!