Creality Falcon2 S value/variable power issue

SO I am using my Creality Falcon2 with LB and it autodetected as GRBL < 1.1e so i switched to 1.1f to use variable output power as my corners were getting burned.

In short, now my laser appears very weak, even at 100% i am getting maybe 1 watt out of a 40w laser. Increasing the S value max to 10,000 while maintaining $30=1000 has improved output power back to normalish levels, seen in lasrgrbl.

I know this is a hack and I am looking for the root cause of the issue.

I am on the latest firmware for my laser which reports as grbl 1.1f.

Furthermore, with the S = 10,000 hack, I am seeing another strange behaviour, at low head velocities (around corners, when changing directions, laser power drops substantially (more than it should to compensate for low velocity), however, when operating at normal speeds, laser power is adequate. im getting no corners now instead of burned ones. If i attempt to engrave an image, the edges are faded while the center appears OK.

Please help. I am very new to laser engraving.

Can you take a screnshot of Edit > Device settings window?

S-value max and $30 need to be the same. If they are not, then the software is sending the values it thinks the controller needs, but are not.

Set S-value Max and $30 to the same value, 1000 is good.

Then see what your machine is doing.

Did you restore all of your old configuration values to the new firmware?


Selecting GRBL and setting the controller parameters correctly for your machine is not a “hack”. A hack would be if you edit the GRBL source code by changing something then re-compile.

$30=1000 should match S-value max=1000. This tells Lightburn and the controller to use the same scale for power (spindle speed) control.

GRBL (vs GRBL-M3) allows the laser to reduce power in the corners when it comes to a full stop when changing directions. You mentioned the fried corners. The Constant Power Mode in the Cut Settings Editor can override this action.

There is a lot of variety, even among the machines from the same manufacturer.

If you are beginning to see these are not Plug-n-Play machines, you are on theright track. Take the time to learn all the amazing things you can do with a 40w laser. You will discover it ia s lot of fun.

And welcome to the forum. There is an incredible amount of knowledge and experience here.

Don’t forget @gilaraujo 's “screnshot of Edit > Device settings window” request.

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Here is the screenshot.

I have previously tested with S = 1000 and $30 = 1000 and this results in very low laser power Re: ~1watt @ 100%

Even with S = $30 = 1000, I am also seeing the low laser power around the edges. I suspect that somehow, when the speed of the head is factored in to calculate the correct laser power output, that too high a speed is being considered, or maybe units are not handled correctly?

Here is typical output, with parameters included:

[MSG:Using cpu_map…esp32-s3]

Grbl 1.1f [‘$’ for help]




Target buffer size found

[software versions: CV50-MASTER-Release V3.0.5 20231129-1110]



[OK] ILmp Link connect ok

inquire_info->power:40W ,CV50-LASER-40W-Release V3.0.5 20231129-1003













































Your firmware seems very modified.
I would $Rst=* in console to set all to defaults

Also your DPI is massive anything above 0.07 on a diode will cause overlap of the lines

Try this 2 files, specially too on lasergrbl if you have it to do a sanity check
Dot Test with Angle.gcode (3.3 KB)
Dot Test with Angle.lbrn (46.3 KB)

I temporarily have my laser set up with a rotary roller and $101=60.375 is specific for that.

I ran your lburn and gcode files with LB and LG and had a good laugh. The result is shown below (similar results for both files):

if you look at the line of engraved numbers underneath, you can see the issue im having where its engraved more strongly toward the middle of the bottle, but very faint at the edges when scanning left and right

I believe the roller is defective, i think i have to open it up and tighten a set screw. The pattern resolves correctly with normal-looking corners and edges when I switch back to Cartesian mode. upon further testing the issue has evaporated when engraving in Cartesian space. I will do further testing when I have time over the next few days and I will report back. Thanks for everyones help so far :slight_smile:

why change Y axis when you can use rotary wizard?

You relly need to run the job on the normal axis hard to tell if the slipping n the axis is due to the bottle moving or the belts or similar

@gilaraujo was correct to question your parameters. These two are typically equal, and I suspect $111 is the correct one. I have a feeling that $110 parameter is wreaking havoc with the power control algorithm in the controller.

When I use my chuck rotary, I do not change any GRBL parameters. I have not used the rollers yet, but the only parameter I MIGHT change is $121, Yaxis acceleration rate. This would only be to give the rollers a soft-start capability.

@gilaraujo also recommended doing the $Rst=* in the Console window. Your results with the Dot Test shows major problems. I suggest you focus more on getting the machine properly working before trying to diagnose burn issues.

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