Every 3D printer fails the same handful of ways, over and over, on every brand and every material. The hard part is not knowing that something is wrong. It is matching what you are looking at to a name, because the fix lives behind the name, not behind a vague description like “my print looks bad.”
This guide sorts the common failures into six groups: first-layer problems, extrusion problems, surface and cosmetic defects, structural and mechanical failures, thermal and safety issues, and the resin-specific failures that do not map onto FDM at all. Each entry links to a dedicated guide with the actual fix. Think of this page as the index, not the destination.
First-layer problems
Almost everything that goes wrong on a print traces back to what happened in the first few layers, so this is the first place to look.
A first layer that will not stick at all usually comes down to a dirty plate, a nozzle sitting too far from the bed, or temperatures that never gave the filament a fair shot. First Layer Not Sticking walks through the checks in the order that actually matters.
Warping is a different failure that looks similar from across the room: the base sticks fine in the middle, but a corner curls up and lifts off the bed as the plastic shrinks while cooling. Stop Corners Lifting covers drafts, bed temperature and brims, with material-specific follow-ups for PLA, PETG and ABS.
If the layer is bonded but the surface underneath it waves instead of lying flat, that is neither of the above. Fix First Layer Ripples traces it to Z offset, flow rate or a bed that is not actually flat.
A lower edge that spreads out past the model’s actual outline, sometimes called elephant foot, comes from too much first-layer squish combined with lower layers staying soft under the part’s own weight. Fix Elephant Foot covers the Z-offset and cooling fixes before you reach for slicer compensation.
Extrusion problems
These show up as thin lines, missing material, or plastic coming out where it should not.
Under-extrusion looks like gaps between lines, weak layer bonding, or a part that feels hollow when it should not. The usual suspects are a partial clog, a slipping extruder gear, or a temperature too low for the speed you are running. Fix Under-Extrusion has the diagnostic order, and PETG gets its own guide since moisture and a colder-than-expected printing window cause the same symptom through a different mechanism.
A full clog is the extreme version: little or no flow even under full pressure. Clear a Clogged 3D Printer Nozzle Safely covers cold pulls, cleaning needles and when to stop and call it a hardware problem instead.
Oozing is a blob or drip that forms at a fixed point, like a pause or the start of a travel move, while the nozzle sits idle over the print. That is a separate problem from stringing, which leaves thin strands between two features after a travel move rather than a single blob. Stop Nozzle Oozing covers heat creep, coasting and pressure advance; Reduce Stringing covers retraction and travel settings for the thin-strand version instead.
Heat creep sits upstream of several of these: filament softening too high in the hotend, above the melt zone, usually from a hotend fan that is not keeping up. Heat Creep Explained covers the mechanism and which guide fits your actual symptom.
Surface and cosmetic defects
These do not usually stop a print, but they make it look worse than the printer is capable of.
Fuzzy skin is a rough, hairy texture on vertical walls, and it can come from moisture, vibration, heat or a partial clog depending on what else is going on. Fix Fuzzy Skin walks through telling those apart, with separate guides for TPU and silk PLA where the same symptom has a different cause.
Visible layer lines are the normal stair-step texture of FDM printing gone more obvious than it should be, usually from layer height mismatched to nozzle size, inconsistent extrusion, or mechanical play. Fix Visible Layer Lines covers each cause separately.
Pillowing is bumpy, uneven top surfaces, usually from thin top layers or weak infill underneath them not giving the top skin enough to bond to. Fix Pillowing covers top layer count, infill density and top-layer print speed.
Small bumps at a seam or right after a retraction, often called blobs or zits, trace back to retraction settings, coasting or the seam position rather than general over-extrusion. Fix Blobs and Zits narrows it down before you start adjusting flow across the whole print.
Ghosting, also called ringing, is a fading wave pattern that appears after a sharp corner or hole, caused by the frame vibrating as the nozzle changes direction. How to Fix Ghosting covers frame rigidity and belt tension before you touch acceleration settings.
A visible vertical line running the height of a print, where the nozzle starts and stops each layer, is the Z-seam. Fix the Z-Seam covers seam position, coasting and painting it out by hand.
Structural and mechanical failures
This group is about geometry failing mid-print, not just looking rough.
Spaghetti is what is left once the nozzle keeps extruding after a part has already come loose or a feature has snapped off, dragging molten filament into a tangle. It looks dramatic, but it almost always traces back to an adhesion failure, a collision, or a filament supply problem that started much smaller. Stop Spaghetti covers recognizing it early enough to save the print, or at least the filament.
Overhangs that droop or curl happen because gravity pulls on the unsupported part of each line while trapped heat keeps the edge soft. 3D Print Overhangs covers how far cooling and orientation can push the achievable angle before supports become the honest answer. A related but distinct problem is a thin, flat feature that lifts well into a print rather than at the base: Fix Mid-Print Curling covers that version specifically.
Supports that lean, snap, or let a model topple while the printer is still running are a structural problem with the support itself, not a removal-afterward problem. Fix Supports Breaking or Collapsing Mid-Print covers density, base contact and cooling.
A print that cracks or splits cleanly along a layer line, rather than along the part’s actual geometry, is layer separation (also called delamination). Fix Layer Separation covers the temperature, cooling and speed causes behind it, including why PETG resists it better than ABS but is not immune.
A nozzle that scrapes or gouges the top of a finished area during a travel move is a clearance problem, not stringing or vibration. Fix Nozzle Dragging covers Z-hop, a stray blob, and a Z-offset that has crept too tight.
Thermal and safety issues
A few failures matter because of what they could do to the printer or the room it is in, not just the part on the bed.
Thermal runaway is what happens when a heater or thermistor fault lets temperature climb unchecked instead of holding steady, and it is the reason every modern printer firmware includes a safeguard against it. The general mechanism and why that protection should never be disabled is covered in the spaghetti guide’s safety note above, with a model-specific check for the Ender 3 if that is what you are running, since some stock firmware ships without the protection properly enabled.
Unstable hotend or bed temperature that oscillates instead of holding steady, rather than spiking dangerously, is usually a PID tuning problem. PID Tuning for 3D Printers covers running the calibration routine on Marlin or Klipper.
Resin printer failures
Resin printing fails in its own ways that do not map onto anything above, since the process is curing light-reactive liquid rather than melting a filament.
A resin print that warps at the edges while the rest stays stuck to the plate is a curing-stress problem tied to exposure time, orientation and vat temperature, not an adhesion problem the way FDM warping is. Fix Resin Print Warping covers all three in the order that matters.
Separately from any specific defect, resin printing carries real safety considerations around uncured resin and ventilation that FDM mostly does not. Resin Printer Safety covers what Formlabs and Anycubic actually document on skin contact, hot surfaces and disposal.
Using this page
None of these guides replace looking closely at the actual print in front of you. A rough surface and a clog can both start from a dirty filament path, and warping and spaghetti can both start from the same loose corner three hours apart. Start from what you can actually see, pick the closest match above, and follow that specific guide rather than changing five settings at once because two of these descriptions sounded similar.