Alignment of Printing Axes
The shafts may have misaligned if the spring in the sliding block comes loose while you were replacing the new sliding block. Ensure that the shafts are straight by aligning the print head shaft with the axle alignment tools. Each of the shaft should fit into the same notch of the alignment tools on both sides of the print head.
Using the axle alignment tools
9) If the shafts are not aligned you may loosen the grub screw of the corresponding pulley with the supplied hex screwdriver, and gently nudge the shaft into place until perfectly aligned. Retighten the grub screw once the shaft is aligned properly, check the alignment again after the screw is tightened. Move the print head around to make sure that it moves freely without requiring excessive force.
Loosening and tightening the pulley for adjustment