People send me photos of failed prints every week. Almost none of them are broken printers. It's nearly always one of these five, and checking them in this order saves hours.

1. Nozzle height, not bed level. Auto-leveling handles tilt. It does not handle a Z-offset that's 0.05mm too high. If the first layer lines look round and separated instead of squished flat and touching, lower it. This is the single most common cause.

2. A dirty bed, not a bad bed. Fingerprints are grease. PEI that stops gripping usually just needs dish soap and warm water, not glue stick and not a replacement.

3. Wet filament. Popping or hissing while printing, fuzzy surfaces, sudden stringing on a spool that used to be fine. PLA absorbs water quietly. Dry it at 45-50°C for 4-6 hours before you touch a single slicer setting.

4. Retraction, after the first three. Everyone jumps here first. Don't. Tuning retraction on wet filament just moves the problem around. Fix moisture, then tune.

5. Cooling on small parts. Drooping and shifted layers on tiny models are usually not enough time per layer. Print two copies at once so each layer has time to set, before you start dropping speeds.

One more thing that isn't a setting: a model that was never made to be printed. A lot of free STLs are game assets with non-manifold geometry and 0.2mm details a 0.4mm nozzle physically cannot produce. No amount of tuning fixes that, and it makes people think their machine is broken.

That's the reason our packs get test-printed before they go out.