I've got a Geeetech Pro B i3 printer (my first 3d printer) and after I've assembled it I started testing the axis. X and Y work well but Z cannot move.
If I disconnect the couplings the motors move by themselves and they move in the same direction.
If I help a little bit the motors, by turning with my hand, they move and sometimes move without helping anymore but it stops after a few seconds.
I don't know what do to. I've measured the rest of the setup to make sure there aren't any big differences that could create tension.
What do you suggest?