Laser losing power while cutting?

I am back with another question about my 100w problem child laser. This question relates to not cutting or partial cutting only when running a full production run.
The material I am using is 7mm BB (but really this could be almost anything). When I do the material tests that are built into lightburn, the laser has zero issues in cutting upto speeds of 20mm/sec over that it obviously has a harder time.
Now the problem is, even though test cuts work perfectly fine, in all corners, when I do a full production run (600x800 area) the cuts do not cut through the material completely. It doesn’t matter how slow I make the machine go or how high of power, the system just doesn’t like to cut completely. This is a machine that was purchased to help with backlogs we were having with our main machine and has been having this type of issues since I got it a year or so ago. I thought it was the alignment, which I meticulously checked and re-checked. After messing with that for a few months with no real improvement, I purchased a replacement tube Incase it was wearing out though it was less than 2 years old.
So now I have a new tube, I have re-validated the alignment, bought a larger chiller (5200) but the laser still seems to loose cutting strength as it works on large cutting projects. Again small projects or material tests have no problem, just longer batches.

Any ideas what I can check? I am about to give up on this one and buy new at this point. I basically have rebuilt this SOB and my give a damn is almost spent. Lol


A similar problem also with a 100 W laser, surfaced recently:

Although we’ll never know the end of the story, the diagnostic test was to blow cool(er) air through the power supply, which mightily improved its disposition and led to the conclusion it was failing at higher temperatures.

The old supply may have a ventilation problem, but a new power supply could be an overall improvement.

Thanks Ed, without too much effort I should be able to test this idea. I swear this machine will basically be 100% rebuilt part-by-part and cost the same price as new. I should have made a mini-series out of this.

Although this may seem cynical, I think a key advantage of cheap lasers is their cheap, readily available, non-proprietary parts. If you’re the kind of bear who doesn’t mind (nay, enjoys) tinkering, cheap lasers teach you how things work and how to make them work again, at an overall cost no more than the fancy lasers (which also fail, requiring fancy techs & parts to fix 'em).

Now, in production use, maybe a fancy laser with a service contract makes sense, but after the third or fourth round of fix-me-up, doing repairs on hard mode might become both cheaper & faster.

Good luck with the supply! :grin:

Do you have a ma meter attached to the machine?

If not you should have.

If you have , what does the ma read when testing compared to a larger run, if there is a difference then I would say your power plant is faulty, as I had a similar issue.

Power - Tube - Alignment…that’s basically the machine.

to describe the issue i had…
When I was running a longer job the power would gradually descrease, meaning it would start cutting all the way through and then after a few mins get worse and worse…This was the tube, getting old and failing, not enough gasses I was told to hold the power.

Replaced tube and power supply as I didn’t know which was wrong.
Then another issue (I had ma meter attached) sometimes cutting would read 28ma, then drop to 4ma, on a straight run, of course the laser stopped cutting though, This was the power (new one) supply was faulty, got another one on warrenty, now machine runs perfectly again.

P.s I buy my tubes direct from EFR in china ( I have contact if you need) this way I get direct from manufacturer with FULL warrenty, not one bought in my country someone imported 8 months (or whatever) ago, that is already old with no warrenty left!!
You say you bought a new tube, would be worth checking the date on it.

Good Luck. Neil

Several folks have described their CO₂ laser as “gradually losing power during a job”, so (I think) we now have enough evidence to suggest replacing the power supply before suspecting the tube has gone bad.

It’s certainly cheaper and easier!

That’s an interesting data point: even a replacement power supply may be intermittently bad.

Neil, i do have a meter on the system, I just keep forgetting to pay attention to it when cutting because I get to fixated on watching the laser do its thing.

As far as the tube goes, i may hit you up on your supplies info just in case. Currently I get my tubes imported directly from Yongli because I have read stories about people buying a “new” tube that has a 2-3 year old date on them. I’m pretty sure that my previous tube was still in good shape but now that it’s swapped out I guess that was just a pricey troubleshooting step.

So has this been officially resolved as a bad or overheating power supply? I have a boss 150 watt that stops cutting through 1/8” acrylic after about 10 minutes. I bought a new tube AND new power supply and neither makes a difference. I can crank the power all the way up and it won’t cut throught. Then the big mystery is I can stop it, move to the same spot it wouldn’t cut through, then run a little 1” circle and it’ll cut through like butter and the focus looks much sharper… without touching anything. It’s not alignment

Hello Spencer, Yes this was resolved. after all the checking and adjusting, this actually was caused by a dirty lens. The build up on the lens, which at the time I swear I cleaned, was just enough to etch the lens. So as the lens did longer hotter runs, the surface damage increased and the cutting power deteriorated. Even with a monster crater in the lens, I could get test patterns/cuts to work, but anything over a few minutes I could actually see smoke coming from the 3rd mirror area. Not sure is this what your issue is but this is now the first thing I check when cuts start going south.