Z-axis progressively tilts more and more during print.
Hi, I have an Prusa Mk3s+ and have a persistent problem where the the Z-axis (X-carriage) tilts more and more during prints. Bed leveling and calibration works, the first layer is usually just fine, but one of the Z-axis motors are too fast, making the carriage uneven after a while. The difference is large, visible to the naked eyes and if I level the Z-axis by running it to the top, it's several millimeters offset just after printing something with a height of just a couple of centimeter.
Last summer, after I've checked the little Z-motor covers, loosening them, turned the trapezoid nuts half a turn, lubricated, calibrated and so on for a while, I just decided to swap the motors around (I needed to elongate the cables) and the problems disappeared. Many successful prints after that, but now my printer has rested for a couple of month and now the problem is back. I don't know if the tilt is in the same direction as before, but I think so.
Thus, every print starts with "some Z issues detected, forcing calibration" and when the carriage is hitting the top, one can easily see the huuge differens in level. I've tried to search for similar problems but every Z-level problems seems to relate to the first layer and/or calibration of the first layer. So let me be clear: I have NO problems with the first layers. I have, no my knowledge, no problems with the PINDA sensor, mesh bed leveling, calibration, Z-offset, etc. My problems always start higher up, after the first several layers. All my parts come out "tilted", with layers separation. It almost like a "reverse elephants foot". The problems start after the first couple of millimeters. And I've checked the frame, nuts and bolts, lubrication and friction times after times, over and over and over again. Swapping the motors "did the trick" months ago, but now the problems are back. I have no clue why swapping the motors worked. But no amount of disassembly of the mechanism, and reassemble with great care seems to work. I hear no strange sounds, and I haven't noticed any visible sudden steps. It just like one motor is a little faster for some reason.
It always the "high" side that lost it dimensions, have the most layer separation and is ugliest, making me believe that one motor is "too fast" rather than the other being "too slow".
I've also checked input current and voltage and motor currents without seeing anything suspicious. I know from earlier experience that the printer works (almost) as good if the voltage is too low, like 21V and only gives problems with high temperature prints such as ABS. Today I make sure of proper 24.5V input voltage and enough current and smoothing. This makes me believe that it's not a driving strength problems either (and, one would think that if drive currents were weak, one motor should lag behind rather than being "too fast").
Have anyone else seen this problems and/or have any idea of what to check next? I don't know if it's of any help, but I using the Bondtech extruder and the Revo hotend and the firmware is the Bondtechs fork for Revo. I don't really know what keywords to use in searching, but everything I find using search engines are problems related to first layers rather than "last layers" so to speak.