Maybe someone here can shed some light on this mystery.
Here’s what happened: I accidentally fired up my fiber laser with the protective cap still on the lens. The beam burned a hole straight through the plastic, a nasty burnt smell filled the air, and I killed the laser after literally two seconds.
When I powered it back up to engrave some steel, it behaved like it was running at maybe 5–10% of its normal power. My first thought was that I’d cooked the galvo. Out of desperation, I swapped out the 100 mm lens (the one I’d been using) for a 225 mm lens. The laser instantly ran at full power again. Swapped back to the 100 mm lens—only 5–10% power. Back to the 225 mm lens—full power. Back to the 100 mm—barely any power.
I finally cleaned the 100 mm lens, even though to the naked eye it looked perfectly clear. Put it back in, still only 5% power. Swapped to 225 mm—full power. Put the 100 mm back in—and magically, it’s now running full power again.
Can anyone explain what the hell is going on here?
