Status of the laser - input needed!

Hi today someone said on slack that the laser was experiencing low power, and while chatting and diagnosing with people, his 10 year old daughter noticed that the red (test) laser beam was outside of the cutting chamber and located on her hand.

This means the laser mirrors must have been severely out of alignment. In my mind something like that just shouldn’t happen. Of course the lid was open when this girl saw the spot on her hand, but the lid itself is super janky and honestly there are plenty if cracks where a severely misaligned laser could escape and burn your eye if you have really bad luck.

Laser mirrors dont just jump out of alignment so if someone can check up on what the situation is and what happened I would really appreciate it. I can’t come in until this weekend but seriously if the laser is so misaligned that it’s not bouncing around on mirrors and aiming toward the bottom of the bed then I question how safe it is to use especially when 10 year olds are around it at eye level.

Any input and judgement call is appreciated!


My immediate judgement would be to unplug the laser (if this has not already been done) and add plenty of signage explaining that it is down.

If the guide laser is off, then so is the actual laser, and any operation would just damage the machine and potentially people nearby.

Maybe @alchemist has thoughts on this?

When are people free for a laser maintenance meetup to figure out what’s wrong, make adjustments, and buy replacement parts?

I’m free sometime this weekend but I’m sure someone can look at it sooner.

My general sense is that the tube is at the end of it’s life. It might be worth WeChatting with the company to ask for a quote.

[ Also as a non-urgent WeChat curiosity, Jarius and others are interested in a lens tube with a smaller kerf for getting better detail. If you can also ask the company about the lenses available (probably a tube that can be swapped out) and cost that could be useful to know. ]

Regarding the mirrors/alignment I honestly have no idea without looking at it. One possibility is someone fiddled with them and another possibility is there’s a mechanical issue that made the mirror randomly go loose. Someone needs to check it out and rule out the latter. I personally have never aligned the mirrors. I know @mcscope and @hzeller did a long time ago.

@alchemist do you have any thoughts on how to figure out if we need a new laser tube? Do we need a power meter to find out?

Also the chiller has been overheating. That’s another thing that needs to be looked at. Probably a maintenance thing and hopefully no replacement of parts.

FYI, today we worked on realigning the mirrors and got the laser back in line. Hearsay is someone pushed the cutting head by hand and that’s when the mirrors got unaligned. It also appears that the laser was run temporarily while the mirrors were misaligned.

The result of unknown individual attempting to run the laser while mirrors are misaligned


David (different David) worked on realigning the two lasers (guide and cutting), cleaning the lens es, and just did a test cut.

It seems to cut decently. 1/4 wood (speed 5, power 75). Cut about 80% through.

Still seems like the power may be low.


Do not use the laser

  1. CO2 laser tubes don’t usually suddenly fail like that, their power tapers off over thousands of hours.

  2. The low power is probably due to a combination of misaligned mirrors and dirty mirrors. Dirty mirrors alone can drop power at the cutting head by 50%.

  3. The mirrors MUST be realigned using the procedure in the laser service manual that’s attached to the wall. You’re dealing with an high-power invisible beam …you can’t just do this “by eye”. Do NOT mess with any of the mirrors in the laser tube compartment …if you screw up the resonator mirror alignment it could be nearly impossible to fix.

  4. The mirrors should to be cleaned using a pure, polar solvent like acetone or chloroform, and using optical quality cleaning swabs. You can’t trust most bottles of solvent at Noisebridge because people have contaminated them.

  5. If the laser tube is overheating it means something is wrong with the chiller. Are the water circulating hoses pinched? Is the heat exchanger on the chiller clean?


I would love to get more others in the WeChat group with the company reps so that I’m not a bottle neck for people asking questions. @David @alchemist @themanmaran would you be interested? If so please add me on WeChat: ruthgrace92

Also at this point I’m down to pay a technician to fix it and tune it up. I imagine our laser cutter could really use a tune up anyways

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There are no kinks in the tubing - and the coolant is flowing appropriately. Pinching the tube (even for a second) results in a Obstruction warning from the cooler. So I believe the coolant flow is fine.

On item #3: your warning came too late. However the re-alignment was done following the mirror alignment guidelines from the manual (below).


The gantry was also realigned as the left side was 5mm forward from the right side. The mirrors now need to be realigned again as this changes the near and far field alignment by quite a bit.

I agree that we need to have a professional come in and do a full check of the machine.

And then we need to maintain it constantly afterwards. Also we should have a small vacuum and cleaning kit for the laser cutter that can be kept locked in a locker.


What seems to be happening (in the weeks before the misalignment ocurred) is power sufficient for cutting for some time and then an unlucky user gets very low power jumping on after. Then next day laser fine. This has happened with chiller temp 25C (normal). To me that seemed inconsistent with a mirror issue because it’s an intermittent problem and mirrors should stay fixed. But then again the assumption that mirrors stay put seems to be false.

I called this place

They charge $150 an hour for a technician (they are in santa clara though, so I imagine it would include travel time).

The technician I spoke to was really nice though – he said that if the tube turns on (glows pink/purple) and we’ve already tried cleaning the optics, to check the pressure of the CO2. Some lasers come with a reservoir that you can use to fix this, and we should check the manual of ours. He said based on our usage (i said a couple hours a day for 3 years) he wouldn’t expect that the tube would need to be replaced. If we go through the manual and can’t figure it out, we can hire him to come take a look.

Let’s organize a meet up this weekend to try to get it fixed. Does Saturday afternoon work for people? Here’s the link on meetup for Saturday 2pm, tentatively depending on people’s schedules.

Edit: meet up has been rescheduled to Sunday


The mirrors might also have some burn damage from when people were running the machine with no ventilation. They’re usually cheap to replace. Ask the laser tech.


Heads up @David and anyone else who was thinking of coming – I’m going to reschedule the Meetup to Sunday so Dany (one of the laser trainers who’s helped troubleshoot the laser cutter in the past) can make it

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@alchemist took a look today and our laser has been used poorly over time. There’s a ton of gunk in it, even in hard to clean places (that would require taking stuff apart to reach). His recommendation was to cancel the meeting on Sunday and just call in the tech. So that’s what I’ll do.

Also I messaged the manufacturer and a new tube would be $800 not including shipping (so probably over a thousand dollars including shipping from China). Checking how much a 150W tube costs on Carl’s recommendation, will report back

$1600 not including shipping for 150W. Called repair tech and he asked me to send him an email with pictures. Will cc David G and alchemist.

edit, just cc’ing david as i don’t have alchemist’s email.

sent this:

Hi Frank,

Here is a link to a Google photos album with the pictures of our laser cutter that I took today:

I’ve CC’d David, who also helps maintain the laser cutter.

The laser cutter is a 100W CO2 laser. The laser says Kaitian on it, but the manufacturer has since changed their name to G. U. Eagle. I am in touch with their customer support team on WeChat. A replacement 100W tube is $800 USD (not including shipping from China), and a replacement 150W tube is $1600 USD. We’ve previously replaced the plastic laser head, lens, and brass air hose adaptor, so I’m confident that any replacement parts we need will be readily available for purchase from the manufacturer. We have had the laser cutter for 3 years, and it sees 2-3 hours of use on average per day.

The problem that we are having is that the power is not what it used to be, and we’re scared that this is a sign of malfunction, and have been careful not to operate the laser cutter. We’ve wondered if there has been burn damage on the mirrors due to people trying to use the laser cutter without ventilation. We have already tried cleaning and realigning all the lenses and mirrors that were easily accessible.

Additionally the chiller has been alarming due to high heat after the laser cutter has been used a while. Maybe there is particulate in the water? Maybe it’s something else entirely?

Do let me know what you think. We’d love to pay to have someone come over to look at it to provide some guidance, and your rate of $150/hr (presumably including travel) sounds reasonable.

Thanks very much in advance – I miss using the laser cutter very much (for prototyping acrylic parts and also cutting fabric for clothing).