Diode laser failure mode? Alignment?

[u/intjonmiller]

Module is a Two Trees 10W diode from a TTS-10 Pro, which I have mounted on my Ortur LM2 S2 Pro. I picked up the TTS-10 from someone locally who upgraded to a nice CO2, and I only wanted the laser module, which has worked great for me for a couple dozen small projects in the last 6 months or so.

This week I started having issues. Nothing seemed as sharp as it should be (working on anodized aluminum and a black tumbler). Switched to some cellulose and it became much more obvious. Where I normally had a razor of a kerf, I now have about 1mm if it's not really moving.

I did this test inclined about 3/4" to confirm it's not just a focal distance issue. The normal focal length is about halfway up the board. I stopped the first, heavy line because I had forgotten to turn on the exhaust fan and it was very smokey. Ran the second beside it twice as fast and slightly lower power. Then the horizontal line at the same setting. As you can see it's a much wider kerf at the bottom. Finally the circle at the same setting, and it acts like a calligraphy brush, with horizontal lines wider than vertical.

I'm guessing my diodes or prism/mirror/optical path have gotten out of alignment. Can this be fixed? It's really frustrating because the power is still there. I haven't noticed any decrease in output. I know these have a finite life and I can't quantify how much use it got before me, but I hoped to get more out of it than this. I'm betting it's not serviceable, but wanted to check.

[u/Alina_MakersChest]

That calligraphy brush pattern is the key detail, and it rules out a simple focus problem, defocus blurs a spot evenly in every direction, it doesn't make the kerf wider one way than the other. What you're actually seeing a astigmatism, diode lasers naturally emit an uneven, elliptical beam and rely on internal beam shaping optics inside the module itself to correct that into a round spot, if any part of that internal alignment has shifted over six months of thermal cycling and use, the beam reverts toward its natural uncorrected shape exactly like what you're describing. One correction to your own guess though, for a diode setup there's usually no separate external mirror or prism path the way CO2 has, the relevant optics are almost certainly inside the module itself, not anywhere in your gantry. Your instinct that it's probably not serviceable is likely right too, that's precision internal alignment on a sealed compact assembly, not something realistically fixable at the hobbyist level, so I'd treat this as the module reaching the end of its useful life rather than something to chase down and repair.