3D print troubleshooting: find the problem by symptom

Most 3D printing problems come down to a handful of recurring causes: leveling, temperature, retraction, extrusion, cooling and mechanics. The trouble is that the symptom doesn't always tell you which one. So this guide starts from the symptom: it shows 17 common defects as simple, consistent side-view drawings you can hold up against your print.

For each defect you see three things:

• What it looks like: one sentence describing the typical symptom, so you're sure you picked the right one.
• Most common causes: in order of likelihood, most common first.
• What to do, in this order: the first step is usually the cheapest and the one that works most often.

Where a tool helps, you get a link, for example to the temperature tower or the e-steps calculator. Search looks through defect names, descriptions and causes, so words like "strings", "corners" or "holes" find matches.

A large share of failed prints start on the first layer. If the nozzle is too high, the line stays round instead of squishing onto the bed, and the part pops off. If it's too low, the line is squashed flat and spreads out, giving you elephant's foot: the bottom layers bulge outward.

What to check first:

1. A clean bed: wash it with warm water and dish soap, then don't touch it. One fingerprint is enough to stop adhesion in that spot.
2. Z-offset: the first layer should be slightly squished, not round and not see-through thin. For elephant's foot, raise it 0.02–0.05 mm at a time.
3. Temperature and speed: 15–25 mm/s for the first layer; bed typically 55–65 °C for PLA and 70–85 °C for PETG.
4. Brim: with a small contact area, or a material prone to warping, a 5–10 mm brim helps a lot.

Warping comes from shrinkage: upper layers contract as they cool and pull the corners up. ABS and ASA need an enclosure and minimal cooling; for a large PLA part, a brim and no drafts may be enough.

Most surface and extrusion problems can be fixed by calibrating. The order matters, because each setting builds on the previous one:

1. E-steps: does the printer actually push out as much filament as the G-code asks for? Extrude 100 mm, measure, and the e-steps calculator gives you the correct value.
2. Temperature: a temperature tower shows the coolest temperature at which layers still bond strongly.
3. Retraction: on a retraction tower, read off the smallest distance where strings disappear.
4. Flow: fine-tune extrusion with a single-wall cube and the flow rate calculator.
5. Speed: the layer height calculator uses your hotend's volumetric flow to tell you how fast you can print without under-extruding.

If stringing persists no matter what, suspect wet filament: PETG, TPU and nylon are especially prone. The guide suggests drying PLA at 45–50 °C and PETG at 60–65 °C for 4–6 hours. Wet filament also pops, leaving blobs on the walls.

If a defect has a regular pattern, or starts at a particular height, the cause is probably mechanical rather than a slicer setting.

• Layer shift: from a certain height the part is offset sideways. Causes include a loose belt, a pulley slipping on its shaft, too much acceleration, or the nozzle catching on a curled edge. Tension the belt, tighten the pulley set screws, and turn on Z-hop for travel moves.
• Ghosting (ringing): faint repeating ripples after sharp corners and lettering. It's a sign of vibration; lower outer-wall acceleration, tension the belts, and calibrate input shaping if your printer supports it.
• Z banding: evenly spaced horizontal ridges. A bent or dirty Z screw, a layer height that doesn't land on whole motor steps, or a fluctuating bed temperature can cause it.
• Spaghetti: the printer is extruding into thin air because the part came loose or fell over. The fix is usually in the first layer or the supports.

Always change one thing at a time and print a small test piece. That way you know what helped, and you don't break a good setting while fixing another.