Offset fill puzzle

Hi folks, first post. For background I have quite a lot of experience with hobby CNCs, but I’m pretty new to lasers.

I’m trying to do an offset fill for the attached image, and getting some strange lines that look pretty deep (higher power than fill). The image looks ok on the PC, and a regular fill works fine without the phantom lines. This happened twice with the same pattern exactly. I’m stumped, but I’m sure user error… Just don’t know what that error is. Any idea?

Offset Fill has very specific uses, and is much more common for diode users than CO2.

Because that shape has sharp points in the offset, every time the laser slows to make those corners, it lowers the power down to ‘Min Power’. You might not have that set low enough, and it’s possible that with it set appropriately your laser won’t even fire - glass tube CO2 lasers, unlike diodes, have a threshold below which they don’t ionize and won’t fire.

Fill works because it’s dirt simple, passing back and forth over the design and not slowing the laser head while the beam is on.

This is technically not an error - it’s just a limitation of the laser.

Thank you Oz for the response. I’ll give it a look when my mind’s had a chance to refresh, and mess around with some scrap instead of the working pieces. The odd part are the deep burns on the mirrored loops. I was running at 15% min, 20% max and 100mm/sec (on a 55 watt marketed machine), and I changed the density/lpi to lighten parts of the image . 10% won’t fire the laser. I also shouldn’t assume the sketch is ok, although there isn’t anything visible that looks wrong.

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