I had a mysterious problem with the Y axis of my 3D printer that required me to try many unsuccessful repairs before discovering the actual problem. The axis seemed to be periodically binding and missing steps. Since my CNC mill was having problems skipping steps due to lead screw resistance, I assumed that the 3D printer was having a similar problem.
My first attempt to fix the problem was to address mechanical issues. The shaft of the original motor had worn to the point that the motor lost alignment with the lead screw. I replaced the motor and added flexible coupling. I also cut a rubber gasket for the Nema 23 motor to allow a bit more tolerance for misalignment. I added set screws to the flexible coupling unit to press against the flats of the two shafts to assure no slippage. I added a generous amount of lubricant to the lead screw and linear bearings. When I restarted the system, skipping on the Y axis was greatly reduced, but not entirely eliminated.
I read that someone solved a CNC problem by replacing a faulty parallel port cable. Mine was certainly a cheap cable, so I replaced it with a very high quality, apparently well shielded cable. Again, I noticed fewer skips, but they still persisted. Finally I wondered if the parallel port of the computer itself was the source of the problem. Since I had a five axis controller installed, I switched the Y axis connection to the D port of the stepper motor driver, and changed the pin settings in Mach 3. This finally fixed the problem. My control computer is quite old and slow, so I will put computer replacement on my to do list. For now, using an alternate axis solved the Y axis problem.
No sooner had I fixed the Y axis than the X axis malfunctioned! I had noticed that the X axis would bind at a much lower maximum speed than ay after installation of the new motor, but I think the X axis motor finally “gave up the ghost.” the much faster maximum speed of the Y axis is very appealing from a manufacturing time point of view, so I will install a new motor for the X axis and hopefully complete my machine repairs. I will install a flexible coupling modified with set screws and a rubber gasket as I did for the Y axis. I am hoping to be ale to increase printing speed significantly after these changes. I am pretty comfortable flipping over the machine and performing such invasive procedures at this point. I am also becoming more skilled at recalibrating the tip and tilt of the heated bed after disturbing the machine.