I got a 7Watts Laser engraving from Laseraxe the laser head Ecan12, when I got the laser it was working perfectly for like 3 months then stop engraving at all and I realized that the focusing lens got burned, Laseraxe sent me a new focusing lens, no charge.
I installed it carefully myself. The laser was working well for about 6 months, not everyday working just like once a week for some minutes. then the laser starts losing power at the point it wasn't able to engrave stainless anymore so I started using it in a combination of packaging tape and electro etching. However, I noticed that the laser still losing power at the point that it wasn't able to cut balsa wood 1.5 mm. so I decided just doing something drastic. I just took the laser head to unscrew the laser focusing lens and carefully cleaned the Laser diode with rubbing alcohol and a mini cotton swab that I made myself according to the size everything was performed under a stereoscope. the result was Amazing, my laser engraver is able to engrave stainless steel again also titanium and cutting wood it is just like new.
I think anyone can do it, just be really careful and do it under a stereoscope preferably.