Homing issue while engraving

Hi All,

I have tried twice to engrave a small (80 X 76 mm) picture on a coaster size piece of birch. Both times it has gotten about 30% into the job and then it randomly tries to home itself. I get the ALARM 3: Homing error and the job comes to a complete stop.

I am still working out the bugs at this point, but I have to say, had this happened in the middle of a larger job on higher quality media, I would have lost my mind.

I am running a Cohesion 3D Laserboard with the GRBL - LPC firmware. I have gone through all of the processes of setting up the machine, it jogs where I tell it, and has done a few small projects without issue. Can you help me understand why it would be doing this?


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Alarm 3 means “abort during cycle”. There are a couple of things that can cause this:

  • You ran the laser head into a limit switch
  • The hardware thinks you hit a limit switch because of electrical interference
  • The hardware browned out or lost power briefly

The “ALARM:3” message on the console is output from the controller being displayed in LightBurn. The “Homing” message that follows it is LightBurn homing on startup, which means the USB connection likely dropped temporarily. That could be electrical noise or bad grounding too.

Since you mentioned this is a C3D LaserBoard, I would follow up with them on their forum, as they do have guidance for how to properly isolate the board from the chassis (I’m assuming K40 because you haven’t said otherwise).


Thanks Oz. Yes it is a K40. I will get with them and see what needs to be done.

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Yes, please post to the Cohesion3D Forum and we will be happy to promptly help you there.


Thank you Ray. I went in the forum and was about to make a post when I found someone with the exact issue. I read the “fix” for the potential short/ground issue and will be correcting it today.

Fingers crossed!

I’m not sure what you’re talking about. It is not necessary to isolate the new LaserBoard.

Well, I am getting the problem in the middle of engraving images. I also see a spark when I plug the power supply into the board. Neither of which is a good thing.

Please contact me in the Cohesion forum and I can give you more details.

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