1. Lines too thick 

• Check the focal length (follow the supplied focal length ruler).

• Check that the laser path is perfectly aligned.

• Check that the laser beam is emitted from the center of the laser head nozzle.

2. Doubled-up lines 

1. First, confirm that the laser spot at the 3rd mirror is right following Unusual laser spot. Correct as needed.
2. If the laser spot is right at the 3rd mirror, check whether the focal lens is clean and whether the laser is emitted from the center of the nozzle.