Step 1. Thread the threaded rod to the nut of both end of X axis.
Step 2. Plug the threaded rod on the X motor end to the left coupling on the left bottom of the Z axis. Then thread the 320mm smooth rod into the linear bearing.
Step 3. Thread the L390mm smooth rod into the X motor end >> thread the extruder carriage on the two rods.
Step 4. Thread the two X axis smooth rods into the hole of X idler end.
Step 5. Plug the vertical threaded rod into the coupling on the right bottom of the Z axis. Then thread the 320mm smooth rod into the linear bearing.
Step 6. Thread 4 locking rings on the 2 rods separately. Screw up the 4 locking rings.
Note. The smooth rods and the threaded rod of Z axis are vertical and the X axis is horizontal, which is very important, or it will hinder the move of the Z axis.