I had yesterday a weird experience while cutting 3mm plywood. I usually use the following parameters for my 100W CO2 laser: speed 15 mm/s, power 25% (using Lightburn). I was cutting a set of small butterflies. I put some 3mm MDF blocks under the plywood sheet, so the cut shapes can fall down and I can see they are well cut. Sometimes, the plywood is not 100% homogenous, and I need to finish the job with a cutter, but never more than a few mm long.
But yesterday, doing the butterflies, the laser stopped cutting through the wood. The light was still there, and seemed normal to me, but the wood wasn’t cut anymore. And this happened not only on a small part of the sheet but for several butterflies. Even with 3 passes, it wouldn’t cut through.
I had to push the power much higher than usual (60%) to have the laser cut the wood again.
Does this sound like my laser is dying? It’s almost 2 years old, and I use it around 5 to 10 hours a week, never higher than 40% power.
I must add that, just after this sad episode, I had to cut transparent plexiglass. I used my usual parameters for up to 10mm thick plexi and it worked like a charm…
Lose of power can be a sign of a dying tube. Sometimes it’s apparent as changing TEM (mode) where you see more than one spot when doing an alignment test.
In my experience with a k40, and moderate usage, 2-3 years has been a normal time for tube life.
It could also be that it was just that piece of plywood. I’ve had 1/4" (6mm) plywood that was much harder to cut than others which appeared to be due to a much thicker glue layer. Plywood glue (urea based) is resistant to cutting with a CO2 laser because it doesn’t burn well. Usually it’s small areas, as you noted, that give us problems which tend to be voids filled with excess glue.
The laser is pretty worthless without the lens and optics. When you have an issue like this it’s best to double check for a clean optical path and alignment.
As was mentioned a pulse on m1 will allow you to check the tem resonance.
It running fine with acrylic, so it’s probably the plywood, most of us have had similar issues…
