A field guide to first-layer problems

1 · Start with the plate

Fingerprint oils are the most common adhesion killer and survive a quick wipe. Wash textured PEI with dish soap and hot water, dry with a clean cloth, and stop touching the print area. IPA between prints maintains a clean plate; it does not rescue a greasy one.

2 · Then trust, but verify, the mesh

Auto-levelling measures the plate; it cannot fix a plate held down by a blob of debris under one corner or a binder clip the probe never saw. Re-run calibration after any nozzle change — a new nozzle's length differs by fractions of a millimetre, which is the whole game at layer one.

3 · Read the line the printer draws

• Rounded, tall bead that barely touches — nozzle too far, or flow too low
• Transparent, dragged-thin line with ridges — nozzle too close
• Good start then peeling corners — plate too cold, or drafts across the bed
• Gaps within an otherwise good layer — partial clog or wet filament

4 · Temperature and speed, last

Only after cleanliness, mesh, and Z are right, tune the numbers: first layer 10–15°C hotter than the body, speed at half, fan off (PLA excepted at low speeds). PETG likes a slightly larger first-layer gap than PLA — it grips too hard when squished and takes plate coating with it on removal.

The five-minute reset

When a machine that printed fine starts failing: wash the plate, re-run bed levelling, dry the filament, then print a one-layer test square. That sequence finds the culprit in one pass far more often than slicer archaeology does.