It seems lots of folks are having the same issue I was… Something’s off in the Z-axis, making transitions up and down rough or wobbly. I found that removing the top bearing support solved all my problems. While it seems like an important thing, it’s really not that functional. What matters is the changing distance between the motor and the extruder arm. With the support bearing in place, the threaded rod has three points of contact, which means the motor, the extruder arm coupler and the top bearing support need to be PERFECTLY aligned to function. Straight out of the box, they are not. By removing the support, any slight bend in the rod or misalignment of the motor drive shaft with the extruder arm coupler is completely forgiven, having reduced the equation to two points of contact. The wiggle-room in the extruder arm coupler in the horizontal direction also helps, but was insufficient with the bearing support attached.
I also tried using a flexible coupler between the motor and the drive shaft, but found I had less consistent layer height.
If you’re having Z-axis trouble, I hope this helps!
