Hello everyone!
I’ve searched through the entire internet and specifically this forum, but I still haven’t found a solution to my problem.
Initial data:
Laptop running Windows 11 Pro.
DIY 3D printer with MKS Gen v1.4 board and Marlin 2.1.3-b2 firmware (I’ve also tested Marlin 2.0 and Marlin 1.0).
LightBurn software (it was the latest free version, but now the trial period is expired).
LaserGRBL software.
Idea implementation:
At first, I bought a 10W laser module (with 12v and 3 pin connection) and printed a small CNC frame to test how everything works. I disassembled two DVD-RW drives, extracted the stepper motors, and installed them in the frame.
Then, I connected the frame to Arduino UNO with a CNC Shield, installed LaserGRBL on it, and set up the software on my laptop.
And — oh, miracle! — it worked! The engraving turned out great, with beautiful shading and very precise detailing.
But! Due to the miniature size of the CNC frame, the maximum engraving area was 5x5 cm.
That wasn’t enough for me, so I decided to convert my DIY 3D printer into a 2-in-1 device: printer + engraver.
At that time, my 3D printer was running on Marlin 1.0, which didn’t have preconfigured laser control, so I decided to go the simplest route first.
The first attempt was the most basic — I disconnected the stepper motors from the 3D printer’s motherboard and connected them to the Arduino.
I reconfigured LaserGRBL for different dimensions and steps, launched the engraving, and — another miracle! — it worked again, producing a beautiful engraved image.
But once again, it wasn’t enough for me!
It was very inconvenient to constantly switch the 3D printer’s stepper motors to another controller, move the printer back and forth, and deal with LaserGRBL’s inconvenient (for me personally) limit switch management…
So I installed LightBurn, downloaded Marlin 2.1.3-b2, configured it for additional laser control, and flashed my 3D printer with the new firmware.
For some unknown reason, the D9 MOSFET output (which is recommended in all manuals for connecting the laser to the fan control output) did not regulate voltage and stays always on 12v (I still don’t understand why it doesn’t work).
So, I connected the laser control to the servo control pins instead.
A new “Laser Control” menu appeared in the printer’s settings, which allowed me to turn the laser on and off.
I configured LightBurn and immediately it detected my printer and successfully homed it.
Everything seemed fine…
And here comes the problem:
To control the laser connected to the servo output, I switched LightBurn to M03/M05 command mode.
I loaded an image, homed the 3D printer, started engraving, and… disaster!
The laser turns on, but the printhead only moves in tiny steps in one direction, simply burning a straight line instead of engraving the image (with noticeable on/off pulses of the laser).
Then, I switched LightBurn to M106/M107 command mode and ran the same engraving job:
Now, the printhead moves correctly along the intended path, but the laser does not turn on, since it’s connected to the servo pins, not to fan pins.
Thinking the issue was in Marlin, I downgraded from 2.1.3 to 2.0, but nothing changed, even though I tried different firmware configuration files.
To verify further, I saved both G-code files (one with M03/M05, the other with M106/M107) and compared them —
the only difference was the laser control commands.
I also compared my Configuration_adv and Configuration files with those shared by other users —
there are no differences in laser control settings.
So my questions are:
- Why does the M03 command adjustments allow the laser to turn on, but prevents the printhead from moving correctly?
- Why does the M106 command adjustments allow correct movement, but LightBurn cannot control the servo output the same way it does the fan output?
I really need your help!
Has anyone encountered a similar issue?
