Framing and leaving scortch marks on the wood

When i frame on my CO2 laser my unit leaves scorch mark on the wood before ingraving

This is interesting.

Your profile says Fox-Alien 4040 so I’d like to know more about your CO2 laser. :slight_smile: What kind of controller does it use?

A wiring problem or some other glitch may be firing the CO2 tube when framing or during other traverse operations. I’d like to know if we should look at this.

In Device Settings there’s a setting to turn off Fire-when-Framing.

Fire-when-framing is fairly-strictly a diode laser feature because the diodes use visible light and the diode can be turned almost off while still being visible. The long infrared is quite dangerous and can’t be turned down as far - or be seen with your eyes.

Depending on your device there may be a switch in Device Settings. It’s toward the middle of the list on the right hand side of the Device Settings pop-up box. The switch is marked “Enable Laser Fire Button”. That switch should be turned off or non-existent for your CO2 laser.

If the switch is there, you can mouse-over it and see some info about it. If the switch isn’t there we should perform hardware tests.

I have MF2028 60W CO2 and an Ortur LM Pro2. I mainly use the CO2 laser for most of my products and occasionally use the Ortur. In lightburn it does not have the fire button under CO2 but does on the Ortur side.

Did this just start happening? … assume you’ve been using it previously…


Mostly since the last couple Lightburn updates

I’m guessing a little bit and presuming the 2028 uses a Ruida Controller and this isn’t controlled with GRBL like the Ortur or the FoxAlien. I took the GRBL tag off the first post.

…Unless you’ve swapped a Marlin controller into it or something - I’ll change it back if you have.

The next recommended (Ruida) troubleshooting step is - With the power off to the laser - put a sheet of paper on the bed of the engraver and generate a quick LightBurn file to mark some small circles in opposite corners. The goal is to see if the paper is marked when traversing. You may want to slow the traverse speed. If framing and traverse are both marking material this symptom could likely be a hardware concern.

This can happen in normal use if the ground screw loosens.

@JohnJohn has a good point… The Ruida and other dsp controllers use two signals to control the laser…

This sounds like some kind of hardware issue… Ensure all wiring is secure… you can ‘gently’ tug on them… sometimes they don’t screw them down, the glue is holding them…

Check the controller for hardware issues, specifically the err LED…

Screenshot from 2022-09-12 11-23-58

You can check the hardware that fires the laser up to the lps pretty simply… On a Ruida…

If the laser is on all the time, check the L-On1 (laser 1 enable, assuming laser 1) output for it being constantly low.

L-On1 is usually wired to L on the lps… if it’s wired to H then the signal is inverted.

If it is not changing states, then a likely controller issue… if it is, that means good to the input of the lps…

All of these signals can be checked with the lps off and I’d suggest that.

Good luck


This now the new problem that I have since Omtech had me reset the default parameters and change the signal level to high.

I assume it’s the laser enable in the controller?

You can check if that’s needed…

Generally the wires are different colors and one of the terminals will be empty… you shouldn’t have to any digging around, just check which color wire is the L-On1 terminal and if that same color wire is on the L or H terminal of the lps.

If it’s on the L terminal, no need to invert the laser enable in the controller.

If it’s the H terminal you do need to invert laser enable in the controller.

Mine goes to L and it is not inverted.


The white-space around the brown duck is filled in dark.
The traverse lines are on.
I’m seeing this as light/dark inverted.
Good call.

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I deleted Lightburn from my computer and reinstalled it and everything appears to be working fine for now. I had mentioned earlier the my trouble started with the last couple of downloads. Now I am wondering if those files we somehow corrupt.