Big Laser abuse

I worked on the Big Laser last night after the meeting as it was reported on the mailing list casually as not quite working right.

The air nozzle (Aluminum cylinder after the lens) was not installed and the air blowoff was taped onto the lens area with blue tape! Luckily I found the nozzle and the thumbscrew and reinstalled it. The air nozzle is needed to direct the smoke/debris away from the lens.

The bed was very misaligned. When the bed was raised so one corner was raised to the “zero” position (aligned with the machine surface the rails are bolted to) the opposite corner was at least 10mm below the surface. This usually happens because something gets stuck between the bed and the edge of the machine while the bed is being raised. This can also happen if the bed is crashed into the laser nozzle. The belt(s) that drive the four lead screws that raise and lower the bed will skip a tooth (or more) if things jam up. This is usually a pretty noisy event and can severely damage the mechanism.

Good news: I was able to reset everything and the test cuts at all four corners of the bed seemed to be OK.

Bad news: Whoever crashed and modified the laser didn’t use the email to report the crash.

We all have things happen while we are using the equipment. If you can’t fix it, please report it ( and leave a note on the equipment that it may be messed up. Leaving the equipment jacked up is not OK. Next time we may create a “Wanted for abusing equipment” poster from the camera feeds. :flushed:

Thanks for getting it back up and running!

Just now seeing this Brad. Not sure about the crash.
I did take the cylinder off as it's still not aligned with the aperture of the cylinder. I left it off because Daniel M. Was also there and wanted to get a cut done but couldn't before I got there as he wasn't aware the laser had been hitting the cylinder.
So like I said, i took it off and left it off so he could finish his cut. I told him how to put it back on when he was finished. Not sure what happened with that as I left when my cut was done.

I popped in the evening to cut a small run took about 3 minutes and the same problem is still going on. The laser is coming through the lens and hitting the cylinder aperture hole somewhere. After the 3 minute cut the cylinder was too hot to touch. YIKES!
I'm not sure what needs to be done.but I'm worried about someone using the laser for an extended period of time and it getting extremely hot.

Let me know what you think.


Thanks for the update.
Sounds like the final laser aperture is misaligned with the beam path. I’ll take a look at it this weekend. When I tested it, things were fine. Perhaps it is loosening up and periodically clipping the beam. The mounting is not the best (single brass thumbscrew). It may be just on the edge of the beam and after a few bounces it gets hit, heated up, and then things get worse. We can enlarge the final aperture a bit and check the surface alignment.

I’d like to ask that you do the ( next time it acts up. That creates a dedicated ticket and flags it for repair.

Good times,


For what it is worth I was cutting with the laser continuously for HOURS on Wednesday night with no issues. if the cylinder was getting hot (admittedly I didn't test it) it would have simply melted with how long I was running it.

heh, there is no amount of time you could point our laser at aluminum to make it melt…

The hole in that aluminum part is purely to accelerate the assist air into the cut right? enlarging it would simply reduce the assist air velocity?

unless there is a consequence I am missing, seems like that would be an easy fix.

The air hole size was a trade off experiment. With a well aligned beam it’s fine. If the beam is not centered you get an eclipse.

One certainty is that it is easy to make a hole larger not so easy to align. The issue being no matter how large you make the hole the beam can still be misaligned and eclipsed.

A case can be made for a little larger hole. But the real key is maintaining axial alignment.

Further rational discussion is required.

I agree.

I’ll try some testing this weekend. Maybe put some paper on the end of the nozzle and see how the beam is aligned relative to the exit hole. The alignment/mounting system for the nozzle is not the most robust. I wonder if it is shifting during operation?
Perhaps a small groove for the thumbscrew to seat into, along with an additional thumbscrew? Maybe get away from thumbscrews altogether?