Corners lifting even with a nice first layer, how did you confirm if it was mesh or plate warp?

[KenAmada]

I’m at that point where I trust my first layer… until I look at the corners. The center lines go down clean and smooth, but the edges act like the nozzle is suddenly too high or the bed is doing something weird. I keep thinking I fixed it, then the next print proves me wrong.

This happened on a big PLA tray I tried yesterday. It started perfect, then one corner lifted and the whole thing slowly turned into a warped potato chip. How did you guys diagnose this without guessing, like what sign told you it was bed mesh tuning, gantry alignment, or an actual plate warp? If you have a simple checklist you follow, I’d love to copy it.

 

[Alan]

For corners lifting with a clean first layer, I separate adhesion from geometry. I do a big single layer test that covers most of the bed and watch the corners while it prints. If the corners look under squished compared to the center, that is mesh or gantry. If the corners look perfect but still lift later, that is usually cooling, temp, or not enough contact area. A cheap straight edge across the plate can also tell you if you have a real warp.

 

[Mrgrta_sour]

It started perfect, then one corner lifted and the whole thing slowly turned into a warped potato chip.

This is usually thermal stress, not just leveling. As the upper layers cool and shrink, they pull the corners up. Try cleaning your plate with 90% isopropyl alcohol (skin oils are corner killers) and turn your fan off for the first 3–5 layers.

If the center is smooth but the corners lift later, it’s an adhesion/cooling issue, not a nozzle height issue