I ran into something today that I think is genuinely dangerous and worth calling out.
I was testing how many passes it takes to cut through 1 mm brass using a 50W fiber. I had a high-power fill running with wobble enabled, and everything was behaving as expected (loud, and cutting fine).
The issue came when I clicked “Pause” in the Live Framing window. The noise stopped, so I assumed the laser had shut off. It hadn’t.
When I moved the brass sheet to check if I had cut through, the laser burned a line across it. The beam was still active at 95% power—the galvo had simply stopped moving.
That’s not just unintuitive, it’s dangerous.
I had assumed “Pause” would disable the laser output. Instead, it only stops mirror movement while leaving the beam on. At a minimum, the Live Framing window needs a clear warning that “Pause” does not turn off the laser. Ideally, Pause should actually disable the beam until “Resume” is pressed.
For those of you running galvos—is this expected behavior that everyone already knows about, or is this as surprising to you as it was to me?
When LightBurn pauses the laser, it’s a single command sent to the controller. We don’t know what state the laser is in when we pause the job, so it’s up to the controller to ensure the beam is off when it’s paused, and turned back on when resumed, so that sounds like a machine fault.
The maker of the laser is unlikely to know, but the card (BJJCZ) maker would.
I believe it’s the Stop (0x20) command. It’s mot infeasible that we have to call the Disable command for the laser as well, but no capture of EZCad commands ever showed that when pausing.
If you connect EZCad2 and pause a job, does it do the same thing?
All of us who work with laser technology know, or should know, the associated risks.
In this specific case, I don’t consider the scratch to the material caused by the laser to be so important, but rather the possibility that, when handling the sheet of material, the laser might reflect where it shouldn’t (mainly the eyes). At this stage, since the machine is stopped, it is assumed that the laser is switched off, so it is expected that the safety glasses will be removed to check the result of the work.
Without a doubt, this is an issue that needs to be addressed and taken into consideration in this machine.
My 60W Galvo the laser powers down when paused. I think in 99.99999% of the cases this would have to be true or it would have been reported a long time ago.
I agree. I believe this would have been reported before if it were happening all the time. Maybe it is specific to my fiber (BWMTech) or the version of Lightburn I am running (2.0.05)
You can feel it if you reach under the beam. And that’s not in focus. I would hate to have the focal point hit the back of my hand. I tried Styrofoam plate, wanted to cut out a little airplane, full power and nothing. Not a scratch.
I spoke to a couple of other people I know who have the same BWM fiber galvo.
One told me he had seen the same behavior once before, where he paused the program and the galvo stopped, but the beam remained active. But he has only seen it happen that once, and he can not reproduce the issue.
So I tried mine again, pausing the program, and the laser behaved as it should. The galvo and beam stopped correctly. The resume started the laser back up normally.
I am 100% certain the beam remained active after pausing when I noticed the problem (I have the damaged material to prove it). But I can not reproduce the issue again (I tried about 20 times)
So this seems to be a very random/rare occurrence. Maybe there is some weird timing that causes the laser beam to remain on when the pause command is issued once in a 1,000 (or 100,000) times.
That would explain why others have not seen/reported the issue. But something is going on that can cause a very dangerous situation to occur sometimes when the pause is clicked.
I just had this happen with my UV laser today. I was setting up the rotary for some glass etching and when I reached under the laser it burned a little. I stopped what I was doing and found I actually selected the incorrect laser in lightburn. I selected my Co2 galvo by accident. Might not be the same scenario but I got burned none the less.
