Trapezoidal nut too tight, Z-axis calibration fails
I have just assembled my MK3 kit, and I am having a problem. I cannot get past the calibration wizard, the furthest I can get is the homing test but after that it always seems to fail almost immediately with "Calibration failed! Check the axes and run again."
During assembly, I noticed that one of the two "trapezoidal motor nuts" fits very tightly on the screw shaft. One spins quite freely, I can flick it with my finger and it will move a few rotations up or down - but the other does not move well at all, and requires me to use my other hand to hold the screw shaft still to be able to move the nut at all. If I do not hold the screw shaft, the motor is forced to turn when I try to turn the nut. It seems that during the calibration, the motors for the Z axis try to turn, but get stuck.
If I cancel the calibration, I can force the motors to move by using the Settings -> Move axis -> Move Z - although I suppose since calibration has not passed it only moves upwards from where I manually place it, it just says "0 mm" even though it's randomly half way up the axis.
Is this a good question?