Super dark cuts

[Joseph Leavell]

I've managed to kind of dial in my cutting parameters for plywood that I've been working with. However, I can't seem to get a 'light-ish' cut edge. It's always pretty dark no matter what, and if I speed up and noticeable amount, it wont cut at all, and that's using my max of 80% power (50w@100%). I tried messing around with manual PWM settings in lightburn (.5khz, .75khz, 1khz, 1.25khz, 1.5khz) and didn't notice any difference in cut speed, or how the cut looks. Can anyone give me a direction to go in, or is it likely that I'm stuck at these settings due to laser power output?

Also, as an aside, should I be focusing my laser on the top face, or part way through the cut? I haven't noticed much of a difference either way...

Thank you all for the information if you happen to have any!

[Pete Cyr]

PWM can not be adjusted in a glass tube co2 laser. (you can certainly change the setting - but that is kinda like writing Porsche on a chevy)

Not sure what speed you are using...OR What material OR how thick it may be
..... try 8mm/sec at 60% pwr on 1/4" ply wood - I don't recommend pwr >80% - try slowing speed if 8/60 wont cut through

[Joseph Leavell]

Right now I'm going 6mm at 80%, I might be able to do 6/60, but I feel like 8/60 will go down... I'm also using a very short focal length lens because it's given me the best results thus far. Should I write this off as a false positive and try a different medium focus lens?

[Pete Cyr]

2" focal lens is the best compromise between cutting and engraving over all.
If you are cutting with a 1.5 focal lens I suspect that is the issue.

[Eric Adams]

You should be focusing the lens in the middle of the material when cutting.

How thick is your material?

Are you using air assist? If so, is it the 'stock' air pump that most of the Chinese lasers use? If so, you might consider upgrading to higher pressure air output. Search "ultimate air assist" and you'll find a ton of videos about it. I've been using a laser for about 3 years now and only learned about this maybe 3 weeks ago. Seems running around 35-45 psi has a huge impact on cutting performance.

Have you confirmed your alignment is all good, and mirrors & lens are clean?

Otherwise, it sounds like your biggest hurdle is the lens if you're using anything less than 2" focal length.

[Joseph Leavell]

As for material depth, like 6mm plywood (I don't know the exact kind, just took samples and went with what cut best). I do believe I'm using a 1.5, I'll snag a 2" meniscus from cloudray and see how that does. Should I invest in a GaAs? I saw that's what russ uses sometimes to some great cuts

[Gene Uselman]

Russ had good luck with a 2.5" GaAs- you might look at his latest vids on lenses- he has soured on the compound lenses for cutting.

[Joseph Leavell]

Yeah, I had seen his newer ones and noticed that. I did notice however, that he might peek in on them due to them lowering spot size (even though it didn't increase cut speed). I was able to get a 2" for my system, had to get a neck-up to 20 mm (mine was 18mm...) and then new lenses for that as well, so after like 120 I figured I'd just see what effect that had and go from there lol. I haven't gotten the ultimate air assist yet, because it seems like the flow out of my current is plenty already (though not very measurable...)