Motors stop, laser keeps firing

Hi guys. My friend is using what I would call a Big k40. Basically the same setup, just with a bigger gantry and a 50 Watts tube. It came with a M2nano boards as well, which we promptly replaced with the Mini Gerbil V2. We also installed the EFI filter on the power line.

Everything works fine, but some times his motors just stop moving and the laser keeps firing on the spot. We have checked every connection, swapped USB cables, tried 2 different computers.

Any suggestions or something you’d need to help us track the problem?

It would be handy if you could give us more information, such as does Lightburn think it’s done or is it ‘busy’.

Do you lose control over the board when this happens…?

Don’t have one of these animals…

Did you remove the ‘pot’ or voltage control from the IN pin and is it all grounded properly…?

You might try this list of options to start with…

Good luck


I’m back with more feedback.
When the motors stop, the green progress bar in Lightburn dissapears, and the word Ready appears.

This is the text we see in console:

-Waiting for connection
Grbl 1.1f[‘$’ for help]
[VER: 1.1f.20190214:]
[OEM: .MiniGerbil:]
Target buffer size found
Project loaded in 119 milisecoonds
Start current
*** Gcode words are made of a letter and a value. Letter not found.
On or near line 461:
Stream completed in 0:12

*** My friend’s software is set to Spanish, so I had to translate this sentence. Hope it makes sense.


Update: his laser profile was created as GRBL. We just swtiched to “Gerbil-STM” which seems to be specially created for Mini-Gerbil.
Testing as I type this