Started having trouble with the Z axis on our printer. It has worked fine for over a year then after adding octoprint to it (which I don't think affected it) I'm having problem with the left stepper motor acting oddly. When the printer homes the left motor seems to hesitate when it starts to move and then again when it changes directions thus making the bed no longer level. I've tried several things already, changed the stepper driver, increased the voltage, changed the stepper motor and checked the bed tramming. In the video you can see the left motor hesitating when I change directions just moving the bed up and down. Anyone have any thoughts?
Did you check the cable ? One test you could do is swap the cables of each stepper motor and see if this will affect the other motor or not.
I agree with @Rob Heinzonlys assesement. Probably a bad connection somewhere. Probably a connector or in worst case in the wire it self.
Lubrication? Plenty of grease is good but wipe of the surplus after running the bed up and down so that it does not attract too much dust and dirt. Lubricate both smooth rods and lead screws. Loose screw? At any of the three points the lead screw passes through, or even the screws holding the Z motor have come loose? Equally if the smooth rods supports are loose they could be out of alignment. The lead screw or smooth rods being out of alignment would cause more friction and cause the motor to stall momentarily (English form of momentarily) A rather extreme test would be to remove the two lead screws and move the bed up and down by hand checking for resistance. The two Z motors are also wired in parallel? so other than a poor connection to one motor it's not likely to be the driver board as both driven from the same one. Swapping the cables is possible but difficult as you would have to do this at the motor end. Y axis smooth rods loose? This would cause the frame (unsupported at the front) to move outwards or inwards creating more friction.
I finally found the problem, it was the wiring. One of the wires going into the connector on the rumba was broken right at the terminal apparently. No visible damage so it must have gotten pinched or bent over and broken somehow while I was working on it. Good news is I've had the whole thing apart and everything has been cleaned and re-lubricated. Had a successful print so I think it is back online. Thanks for all the help!