Most troubleshooting threads try to cover every possible 3D printing problem in one wall of text, which makes it hard to find the fix for the one failure actually in front of you. This guide works the other way: match your symptom to a cause, jump to that section, fix the one setting responsible, and reprint — without re-tuning things that were never broken.
Print failures by the numbers
- 100°C — the bed temperature Prusa’s knowledge base recommends for ABS (80-110°C depending on part size), the single biggest lever against warping on high-temperature filament.
- 4-6 top layers at roughly 5-6x layer height in thickness — the combination most commonly cited to eliminate pillowing (pitted, incomplete top surfaces) without just cranking fan speed.
- 100% fan speed on top layers fixes pillowing on PLA and PETG, but the opposite applies to ABS, ASA, and nylon — those materials warp more with aggressive cooling, so fan speed should drop instead of rise.
- 0.02mm — the tolerance a single-wall-cube flow test should land within on a 0.4mm nozzle before under- or over-extrusion is considered fixed, per the flow-rate calibration test in our calibration guide.
Common problems at a glance
| Symptom | Likely cause | Fix |
|---|---|---|
| Corners lift off the bed, part warps upward | Uneven cooling (ABS/PETG shrinkage) | Raise bed temp, add enclosure, use a brim |
| Print suddenly offset mid-way through, clean otherwise | Skipped steps — belt or acceleration | Check belt tension, lower acceleration |
| Visible gaps between wall lines, weak top surface | Under-extrusion (clog or low flow) | Cold pull, run flow-rate test |
| Blobbing at corners, oozing, rough surface | Over-extrusion (flow too high) | Lower flow rate 2-5%, retest |
| Pitted or incomplete top layer | Insufficient cooling or too few top layers | 100% fan (PLA/PETG), add top layers |
| Nozzle stops extruding, clicking extruder gear | Partial or full nozzle clog | Cold pull, or nozzle needle if that fails |
| First layer bulges out wider than the rest of the part | Elephant's foot (first layer squished too flat) | Raise Z-offset slightly, reduce first-layer squish |
| Layers visibly separate or crack apart | Nozzle temp too low or cooling too aggressive between layers | Raise temp 5°C, reduce fan on inner layers |
| Thin hair-like strands between parts | Stringing (retraction/temp/moisture) | See our dedicated stringing guide |
1. Warping and lifting corners
ABS and PETG shrink measurably as they cool from printing temperature to room temperature, and if one side of the part cools faster than another — a draft, an AC vent, an unheated room — the corners curl up off the plate before the print finishes. Prusa’s knowledge base puts ABS bed temperature at around 100°C (a range of 80-110°C depending on how large the part is) and recommends an enclosure for high-temperature filament specifically because ambient air temperature, not just bed temperature, drives whether a part stays flat. A brim (a wide first-layer skirt attached to the part) or, for stubborn parts, a printed draft shield around the object both help retain heat where it matters most — right at the corners.
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See our bed adhesion guide for the brim settings and plate-cleaning steps that prevent lifting before it starts.
2. Layer shifting
A layer shift — where everything above a certain height suddenly prints offset from everything below it — means a stepper motor skipped steps mid-print. The three usual suspects, in order of how often they’re actually the cause: a belt that’s loose enough to slip under load, acceleration or speed settings pushed higher than the printer’s frame and motors can reliably hit, or something physically catching the print head (a loose cable, a knocked-over part, a fan shroud rubbing). Belt tension is diagnosed with a round test print rather than by feel — see the belt-tension section of our maintenance guide — and it’s worth ruling out mechanical obstruction before touching any slicer setting, since no amount of acceleration tuning fixes a physical snag.
3. Under-extrusion and over-extrusion
Single-wall-cube flow test
- Slice a cube with 1 perimeter, 0% infill, at your normal wall settings.
- Measure the printed wall thickness with calipers — on a 0.4mm nozzle it should land within about 0.02mm of 0.4-0.48mm.
- Reads thin (under-extrusion) → check for a partial clog first, then raise flow rate by the percentage difference.
- Reads thick, or corners show blobbing (over-extrusion) → lower flow rate 2-5% and reprint.
Under-extrusion shows up as visible gaps between wall lines, thin or missing top surfaces, and sometimes a scratchy or clicking sound as the extruder gear slips on filament it can’t push through fast enough — that last symptom usually means a partial clog rather than a flow setting, so a cold pull (below) is worth trying before adjusting flow rate. Over-extrusion is the opposite failure: too much plastic pushed out shows up as blobbing at corners, stringy oozing, and rough or bulging surfaces, almost always traced to a flow rate or extrusion multiplier set too high for that spool.
4. Pillowing (rough or pitted top layers)
Pillowing — a top surface with small pits or a puffy, uneven look instead of a smooth finish — comes from the top layers not fully bonding to the infill below or each other, usually because they cool too slowly. The fix that resolves most cases: cooling fan at 100% by the time the print reaches its top layers, 4-6 top layers instead of a slicer’s sometimes-too-low default, and top layer thickness set to roughly 5-6 times your layer height so there’s enough material to bridge infill gaps cleanly. The one exception is high-temperature filament — ABS, ASA, and nylon are prone to warping and layer separation under aggressive cooling, so those materials need fan speed turned down, not up, and should rely on extra top layers and thickness instead to fix pillowing.
5. Clogged nozzle and clicking extruder
A nozzle that stops extruding mid-print, paired with a clicking or grinding extruder gear, means filament is jammed somewhere between the drive gear and the nozzle tip. Start with a cold pull: heat the nozzle to printing temperature, load a short length of filament to the hotend, then let it cool a few degrees below printing temperature before pulling the filament straight out in one motion — the partially-solid plastic drags trapped carbon or debris out with it, and it works for the majority of clogs without any disassembly. If a cold pull doesn’t clear it, a nozzle needle sized just under your nozzle diameter (a 0.35mm needle for a 0.4mm nozzle) can poke the blockage through from below while the hotend is hot; a full teardown is rarely the first thing to reach for.
Diagnosing a print failure often means ordering a replacement part same-day — a free Amazon Prime free trial covers fast shipping on the nozzle, PTFE tube, or belt a failed print points to needing.
6. Elephant’s foot
Elephant’s foot is a first layer that bulges out wider than the rest of the part, caused by the nozzle squishing that first layer too flat against the bed — often from a Z-offset set too close, or a bed temperature high enough that the first layer stays soft and spreads under the weight of the layers printed on top of it. Raising Z-offset by a small increment (Prusa’s own guidance describes the target first layer as looking like an “orange peel” — slightly textured, not glassy-flat) usually resolves it; see the first-layer squish section of our bed adhesion guide for the exact adjustment steps.
7. Layer separation and delamination
Layers that visibly crack apart or peel away from each other under light stress mean adjacent layers didn’t fully fuse — either the nozzle temperature was too low for that filament to bond properly, or cooling between layers was aggressive enough to solidify each layer before the next one could weld to it. Raising nozzle temperature in the same 5°C increments used for stringing troubleshooting is the first fix; if temperature is already correct, reducing fan speed on internal layers (keeping it higher only on the very top) usually restores bonding without reintroducing pillowing.
Troubleshooting, in one paragraph
Match the symptom, not the printer model: warping is a heat-and-cooling problem (bed temp, enclosure, brim), layer shifting is mechanical (belts, acceleration, obstructions), and extrusion issues (under, over, pillowing, elephant’s foot, delamination) all trace back to a small set of calibration numbers — flow rate, Z-offset, temperature, and fan speed — covered step-by-step in our calibration guide. Fixing the right one setting beats re-tuning everything every time a print fails.
Related guides
- 3D printer calibration: the complete step-by-step guide — the flow-rate, Z-offset, and PID tests referenced throughout this guide.
- 3D printer bed adhesion: the complete fix list — brim settings and first-layer squish, covered in depth.
- 3D printer maintenance schedule — belt tension testing and the mechanical checks that prevent layer shifting.
- 3D printer stringing: why it happens and how to fix it — the dedicated deep-dive for stringing specifically.
- Best 3D printer nozzle: brass vs. hardened steel vs. ruby — nozzle needle sizing and cold-pull background.
- Is Amazon Prime worth it for 3D printing shoppers? — the break-even math on fast shipping for replacement parts.