Etching cardboard

I am working on etching designs in cardboard and it looks like a fine line between scorching the surface and cutting through. I have been lower the bed ~10mm out of focus as part of this effort. The issue I am having is the etch marks being much darker in the corners or where lines end. See attached for a recent test where I was modulating the min / max power levels in attempt to achieve more uniform burning. For an idea of the range: 20 - 30 max / 12 - 15 min and I have tried adjusting one then the other and both though am unable to achieve a uniform etch. Strangely when lowering min power, rather than making the corners lighter, the light between the corners is made lighter. Could this be because I am working to the lower end of the power scale where uniformity essentially breaks down?

IMG_20240627_152156 (Small)

There are many different units to mark speed with… please let us know. inches/min, mm/min, mm/s or …?

How much power is your machine?

How big are these squares and how fast are you running?

Can you look and see what your machines start speed? Edit → Machine Settings → Start speed

If you run at or below the start speed, it will only use minimum power setting.


So getting the settings optimized for etching cardboard seems like a fine line between too much and too little power if one is trying to avoid cut through. Putting the laser out of focus could be a big assist. Also gleaned from youtube is that the power of the laser may also be adjustable at the hardware level of the controller, in this case Ruida 644XS. This would seem to provide a more granular adjustment in Lightburn, since the current default provides only a small range to work within (12-25 power).

The rectangle shown is 1.25" square
the last setting I was using is 500mm/s and 20max/14min
laser is 100W CO2
start speed: 10mm/s