Laserboard/Lightburn - Circles are oval

Machine: K40 w/m2nano

Board: C3D Laserboard w/Lightburn

Firmware: Problem occurs with both Smoothie and GRBL

Problem/ Question: Board was working originally, but lately when I try to cut a 16mm circle, I get an oval that’s 16mm wide and 18.5mm tall. The Y-axis is stretched for some reason. I’m cutting at 5mm/sec, so speed is not likely the issue.

Here’s the baffling part - when I position the laser head using the grid in Lightburn, the problem doesn’t occur. I moved the laser to four corners of a 20mm grid on-screen and burned a spot at each corner. The spots were exactly 20mm apart in both X and Y direction.

What would make the Y-axis move correctly during positioning, but then be stretched during a laser cut? I did check the steps/mm in lightburn and they are set the same. Happens the same with either smoothie or GRBL installed. Any ideas?

Possibly a loose or stretched belt slipping.

Forgot to disable rotary mode in LightBurn?

YES! Thank you! I recently upgraded to a newer version and didn’t realize the rotary setups went back to default settings. I had the rotary set up for A-axis and it defaulted back to Y-axis. Woop woop! :smile:

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