Engraving is getting dimmer after a while


My CO2 laser engravings get dimmer after 15 min, no matter the position in bed. I’m desperate. If I engrave five pieces, 5 min each, at the same position, it gets dimmer from the 4th. If I turn off the machine and turn on after some minutes, it works again for 15 min.
Water temperature is constant at 18-20ºC. Checked and cleaned lens and mirrors, they are in very good shape. Object are aligned within ± 0,25 mm aprox or better with a 2.5’’ focal length lens.

Can anyone imagine what could be happening?
Thank you!

I’d lay long odds on the power supply fading away.

The only way to know is with a milliammeter displaying the tube current, which should be pretty close to the same for each piece. If it declines steadily, then the power supply is unable to maintain the proper tube current.

AFAICT, power supplies are consumables, so you may as well order one, install it, and see if the situation improves.

Another possibility is the laser tube fading away, but that seems unlikely. Given that you’d want to replace the power supply before assuming the tube has failed, getting one now makes as much sense as anything.

The tube temperature also affects the power output. If you’re running an active water chiller with a thermostatic control, then seeing a constant water temperature makes sense: the tube is being properly cooled. In contrast, I’m using a low-buck icemaker, so the temperature tends to rise during extended sessions; if it remained constant, that would be an indication both the water pump and the water flow sensor failed, overheating the tube. This is almost certainly not your problem, but worth ruling out Just In Case.

Just dropping an update here about the issue I’m dealing with my CO2 laser.

So, I went ahead and got myself a new MYJG100W power supply, but the engravings keep getting dimmer after about 5-10 minutes of use.

I got all curious and decided to do some investigating. I ran a little test where I kept the laser going with the “Test” button and kept an eye on the ammeter. To my concern, the amperage slowly dropped over time, starting at 0.5 mA in the first minute.

Additionally, when cutting with this new power supply, I’ve noticed that the laser only utilizes power up to somewhere between the Min and Max Power settings, never reaching the maximum power even with straight lines (if Min Power is 12% - 5mA and Max Power is 26% - 11mA, it only reaches 7mA, but if both Powers are 26%, it reaches the 11mA). Has anyone else encountered this problem? Should I start a new topic to discuss this issue? I’m starting to worry that this new power supply might be defective. Any insights would be greatly appreciated!

Oh, and check this out: I noticed that the purple beam inside the laser tube is doing this funky circling dance in the anode, kinda like in this video (https://www.youtube.com/watch?v=si7VySd86J0), though without any noise. I’m not sure if the arcing happened with the old power supply. I’ll check it out tomorrow. I wonder if this has any connection with the power decrease issue?

I did some research, and I came across two opinions on this matter. One considered it normal, while another suggested that it might be attributed to the presence of algae. However, I must clarify that I do not have any issues with algae, as the water I use is distilled and contains a small amount of cooling liquid.

So, I’m a bit stumped, and that’s why I’m turning to you for some help. If anyone’s got any ideas or suggestions, I’d be ever so grateful.

Thanks a bunch for lending an ear (well, eyes) to my laser dilemma!


Opinion: now that you’ve eliminated temperature variations and the power supply, what’s left is the tube.

Given that the crud is outside the laser cavity, I’m reasonably sure it has no effect on what happens inside. But, then, I might just be another guy who’s wrong on the Internet. :grin:

I am going to buy a new laser, anyway the one I have has already lasted 3 years. ednisley thank you for your replies!

Regarding this issue:

I’ve found the correct answer in this forum:

I’ve received the new laser I purchased. It’s a 90W RECI W2 laser. I initially thought I had bought the best, but now I think I might be one of the unlucky ones…

It turns out it has what I believe to be a defective laser beam, as it outputs a laser beam in the form of a disk.

I will open a new topic for this issue, as it is a different one, but I’m not closing this one for now because I have not yet verified that the milliamps don’t drop anymore.
This is the post: 90W RECI W2 laser tube outputs concentric circles