Most beginners blame the STL. It's almost never the STL.

If the first layer curls, the bed is too cold or the nozzle is too far. Pick one, change one thing, print a 20 mm square.

The test

1. Heat the bed to what the filament actually wants (PLA: 60°C, PETG: 70–80°C). Wait until it holds that temp, not just “reached.”

2. Drop Z-offset 0.05 mm. Not 0.2. 0.05.

3. First layer at 25 mm/s. No infill. No walls. Just a square.

If the square is shiny and you can barely scratch it with a fingernail, you're done. If it's matte and you can peel it, you're still too high.

That's the whole game. Files that are designed around this test print the first time. Files that ignore it waste a roll.

I keep a pack of those test-first models in MeshWorks. Separate from live support — support is a 1-hour session that expires in 7 days, not a forever help desk.