I would not expect coarse machine work to affect reflection; the beam shouldn’t touch the metal of the head at all, nor the metal of any of the mirror holders before the head.
I can’t remember whether we’ve shared this with you before, so just to make sure you have this information easily to hand, from K40 initial setup and regular maintenance: Alignment
The path that the laser takes along three mirrors and the lens needs to be precisely aligned. Here are three resources that may help you understand how to do this.
If you prefer video instruction:
Ep6: Laser Beam Alignment. The DIY CO2 Laser Cutter / Engraver Build Series
If you prefer written instruction, here are two guides:
- The “Tim the Floating Wombat” guide: K40-Alignment-Instructions.pdf
- The “smokeandmirrors” guide: laseralignment.pdf
Note that if the third mirror does not align the beam with the middle of the lens, the beam will not be focused correctly and will not be aligned with the hole in the nozzle. You may wish to use a device that helps you align using a red visible laser. One kind uses a “beam combiner” that slightly reduces beam power, and the other is a tool used only while performing alignment .
