Why is my laser getting "lazy" on random lines?

Accessories J Tech Laser
1

I have the 7W JTech laser, and I keep having this issue while cutting bristol paper where it will randomly decide to perf some lines, or it will start and stop cutting too early leaving unwanted tabs on the corners of cuts. (See image for examples - none of the lines are supposed to be perfed or tabbed.) The cuts are imported into Lightburn (v 1.7.03) from DXF files that I made in Autocad. It also only seems to happen on cut-throughs, not on the low-intensity decorative burns. It also seems to be worse on bigger files - the photos are all from one 35min run.

Settings on that layer are:
8mm/sec, 100% power, single pass
150ms start pause time, cut-through
Everything else is disabled.

Any leads on what this could be would be appreciated!

PXL_20250504_232321181
PXL_20250504_2323211811920×2550 128 KB

2

Maris,

It could be your minimum power setting being too low. I see this on my CO2 laser sometimes, as Lightburn ramps down the power approaching an end of vector to prevent the slow down to change directions sends the laser to a low power setting to prevent “scorching” the corner. If your running 100% power on the high side, try 40 - 50% on the minimum and see if that helps.

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3

How do I change the min power setting? I only see a box for “Max Power (%)”. Also, FWIW, I have tried Constant Power mode and it made no noticeable difference.

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4

The GRBL processor in Lightburn for the JTech lasers (GRBL 1.1e or earlier) doesn’t have a min power setting like you’d see on the Ruida or GRBL 1.1f processors.

5

The issue I’ve seen on lines with my 44w on an elite, is a “stutter” at the beginning of the line where the machine moves in a couple jerky moves before moving smoothly along the line. From my research this is related to the relatively ‘dumb’ nature of the machine processor (also means you can’t do the min power (and a few other things). Though I’m not sure if that’s what’s going on with yours or not.

If part of the material is waste you may be able to try lead in/out to help with your specific issue.

Another thing to check is to ensure that the lines in Lightburn connect at the corners.

If you can, post the file and I can give it a look/test.

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