I have a cheap bedslinger, an Anycubic Kobra 2, and generally it's a pretty decent printer at the price. I have flashed klipper FW on it, so I'm not using Anycubics FW.
I have issues whenever I try printing bigger parts, the first layer is always complete shit (see post photo).
Heightmap, measured with inductive probe
range is only 0.085mm from min to max, so it should be reasonably flat. The heightmap is automatically recalibrated and loaded as part of my print_begin macro.
Slicer settings for line width
I don't know if my printer just doesn't correct Z-height during first layer, if my line width settings are completely messed up or what is causing this, but the issue is only apparent on bigger parts with large contract surface on the bed.
[SOLVED] It was just Z-offset that was too low causing this. however when running the calibration routine from ellis3dp on first layer squish, the settings that looked good on the small calibration patches, looked like crap on bigger prints. I needed a bit higher Z-offset, but that solved it.
As others have said, almost certainly nozzle too close to bed. Check your printer for a Z offset setting and click it up .1 or so.