Reduced power when in laser mode

My first post, apologies if I have netiquette incorrect.
I have a Banggood laser engraver with a 3W led laser diode. Arduino controller with grbl1.1h firmware.
I use the laser to cut thin balsa.
With gbrl driver, what happens is when cutting complex curves or circles, the laser movement stutters, never reaches full power and the result is only a partial cut. When it is stuttering, laser power drops to a very low value. When multipass is used, the stutters are in the same place. The input file is autocad 2000 dxf format.

If I set $32=0, I get full power permanently as expected but the stutters in the same place then overburn the cut.

The interesting thing is that if I create a simple drawing using the lightburn drawing tools, in this case, a box with an intersecting circle and a few random overlapping lines, the laser behaves as expected, power looks normal and there is no stuttering.

On the DXF file, I have grouped all the arcs to form a contiguous curve but that made no difference. This video shows what is happening

Any thoughts or suggestion? I am running the latest version of lightburn on a newly built laptop



A group of lines is still just independent objects - grouping them doesn’t make them continuous. It would be a bit like you taking 12 pieces of string and arranging them in a circle on the floor. Unless you “sew” them together, they’re still distinct entities. In LightBurn, ungroup the file, then use 'Edit > Auto Join Selected Shapes" to do this (Alt-J).

DXF files are notorious for this - you’re much better off exporting as AI or SVG if the software you’re designing in supports that.

Regarding the speed, Laser Mode ($32=1) means that the controller ramps the power as the speed changes. It will also reduce the power output if the laser can’t get up to the requested speed, either because it doesn’t have room, or because the firmware speed limit it lower than the requested speed.

Thanks Oz
Your suggestion didn’t work unfortunately, however your explanation of laser mode gave me the clue I needed. I simply dropped the cut speed down from 600mm/min to 300mm/min and it worked perfectly, with nice clean corners.
I also tried with an ai file type and join selected shapes. In fact, the fix may be a combination of all 3 but there was no obvious improvement until I reduced the speed. I need to experiment a little more but I am significantly further forward than I was yesterday. Very much appreciated


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