3D Printer Troubleshooting (2026): Fix 10 Common Print Failures

Quick guide: Diagnostic order First layer Stringing Warping Under-extrusion Layer shifts Quick reference FAQs

Work the problem in this order

The fastest way to fix 3D printer troubleshooting problems is to stop guessing at settings and instead rule out causes in order of how often they are actually to blame:

The plate. Is it clean, is it flat, and is the nozzle at the right height? This is the cause of more failures than everything else combined.
The filament. Is it dry, and is it the temperature the manufacturer prints it at? Moisture mimics a dozen unrelated symptoms.
The temperatures. Nozzle, bed, and chamber. Too hot causes stringing and blobs; too cold causes weak layers and clogs.
The mechanics. Belts, pulleys, gantry squareness, extruder gears. These cause repeatable geometric defects.

The one rule that matters: change a single variable per test print, and use a small test model so a failed test costs five minutes, not five hours.

First layer will not stick

This is the number one failure. Fix it in this sequence:

Wash the plate. Dish soap, warm water, and a full rinse. Skin oils are invisible and they defeat every other fix. Isopropyl alcohol removes some residue but not oils.
Re-run bed leveling and check the Z offset. A correct first layer looks slightly squished, with lines fused into a solid sheet and no visible gaps. Round, separated lines mean the nozzle is too high.
Match bed temperature to material. Roughly 55 to 65 °C for PLA, 70 to 85 °C for PETG, and 95 to 110 °C for ABS and ASA. Confirm against the spool label, which always wins over a generic chart.
Slow the first layer to about 20 mm/s and turn the part cooling fan off for that layer.
Add a brim for tall parts with small footprints. It is the cheapest insurance in printing.

Watch for the surface, not just the setting. Smooth PEI wants a slightly cooler bed than textured PEI. Glass usually needs adhesive. If your plate has a shiny worn patch in the middle, the coating is gone and no setting will save it.

Stringing and blobs

Thin hairs between parts, zits on the surface, and whiskers on travel moves all point at the same short list:

Dry the filament. PETG and TPU absorb moisture in days in a humid room. Water flashes to steam in the nozzle and spits filament out during travel moves. Dry at the manufacturer temperature for four to six hours, then store in a sealed box with desiccant.
Lower the nozzle temperature in 5 °C steps and print a temperature tower. Hotter plastic is runnier and strings more.
Tune retraction. Direct-drive extruders usually need 0.5 to 1.5 mm; Bowden setups need considerably more. Increase in 0.2 mm steps and stop as soon as strings disappear, because excess retraction causes clogs and gaps.
Enable travel avoidance (combing) so the nozzle crosses open air less often.
Check for a worn nozzle. An ovaled brass nozzle after a few kilograms of abrasive filament oozes constantly. Nozzles are consumables; replace, do not diagnose.

Warping, lifting, and elephant foot

Warping is a thermal problem. As plastic cools it contracts, and if one region cools faster than another the part pulls itself off the plate.

ABS and ASA need an enclosure. This is not optional. A room draft across a printing ABS part will lift it every time.
Turn the part cooling fan down for high-temperature materials. PLA wants full cooling; ABS wants almost none.
Raise bed temperature 5 °C and add a brim of 5 to 8 mm for large flat parts.
Round or chamfer sharp bottom corners in the model. Sharp corners concentrate the peeling force.

Elephant foot is the opposite problem: the first layer bulges outward because it is squished and hot. Fix it by lowering bed temperature slightly, raising the Z offset a hair, or enabling your slicer's elephant foot compensation at about 0.1 to 0.2 mm.

Under-extrusion, gaps, and weak parts

If walls have gaps, top surfaces show pinholes, or parts snap along layer lines:

Check for a partial clog. Heat the nozzle and extrude 100 mm by hand. If it curls, stutters, or comes out thinner than the nozzle, do a cold pull or replace the nozzle.
Inspect the extruder gears for ground filament dust. Clean them and set idler tension so the gear grips without flattening the filament.
Raise the nozzle temperature 5 to 10 °C. Fast printing needs more heat than the same filament at slow speed.
Calibrate flow rate and extruder steps. Print a single-wall cube, measure the wall with calipers, and correct the flow multiplier to match the nozzle width.
Increase wall count, not infill, for strength. Three or four perimeters does far more for part strength than raising infill from 15 to 40 percent.

Layer shifts and dimensional errors

These are the mechanical failures and they have mechanical fixes:

Layer shift mid-print: belt tension (a plucked belt should sound like a low musical note, not a slack rope), a loose pulley grub screw, or acceleration set higher than the frame can handle.
Ringing or ghosting (echo lines after sharp corners): reduce acceleration and jerk, tighten belts, and make sure the printer sits on a solid surface. A printer on a flexing IKEA shelf will ghost forever.
Z banding (regular horizontal ripples): clean and lubricate the lead screws, and check that the Z coupler is not binding.
Parts a fraction of a millimeter off: this is usually the slicer's horizontal expansion and hole compensation, not the machine. Print a calibration cube, measure, and adjust once.

Quick reference: symptom to cause

Symptom	Most likely cause	First thing to try
Print detaches mid-job	Dirty or worn plate	Wash with dish soap, add a brim
Hairy strings between parts	Wet filament	Dry 4–6 hours, then retune retraction
Corners curl upward	Uneven cooling	Enclose, raise bed temp, cut fan speed
Gaps in top surfaces	Under-extrusion	Cold pull, then calibrate flow
Layers offset sideways	Lost steps	Belt tension and pulley grub screws
Rough bubbly surface	Moisture in filament	Dry the spool
Bulging bottom layer	Elephant foot	Enable 0.15 mm compensation
Nozzle drags on the print	Z offset too low or curling	Raise offset, check part cooling
Clicking extruder	Clog or too-fast flow	Raise temp, slow down, then clear nozzle
Weak, snappy parts	Too few perimeters or too cool	Add walls, raise nozzle temp

Maintenance that prevents most of this

Wash the build plate every few prints, and never touch the print surface with bare fingers.
Store filament sealed with desiccant. A cheap dry box pays for itself in one avoided failed print.
Replace brass nozzles roughly every 3 to 6 kg, sooner with abrasive filaments.
Check belt tension monthly and lubricate lead screws every few months.
Keep a working profile saved. When a print fails, being able to return to a known-good baseline is worth more than any single setting.

If your machine fights you on every print despite all of this, the machine may simply be past its useful life. Our current picks are in the main guide: Compare our 3D printer picks.

FAQs

Why is my 3D print not sticking to the bed?

In order of likelihood: the nozzle is too far from the plate, the plate is greasy from fingerprints, the bed temperature is too low for the material, or you are printing too fast on the first layer. Wash the plate with dish soap and warm water, re-run auto leveling, and slow the first layer to about 20 mm/s.

How do I stop stringing?

Dry the filament first, because wet filament strings no matter what you do to retraction. Then lower the nozzle temperature in 5 degree steps, increase retraction distance slightly, and enable combing or travel avoidance in your slicer.

Why did my print warp and lift at the corners?

The part cooled unevenly. Raise the bed temperature, close the enclosure or block drafts, add a brim, and reduce part cooling fan speed for ABS and ASA. PLA rarely warps unless the bed is too cold or a fan is blowing directly on a corner.

What causes layer shifts halfway through a print?

The toolhead lost steps. Check belt tension, look for a loose pulley grub screw, make sure nothing is obstructing the gantry, and reduce acceleration. A cold print that shifts at the same layer every time usually means the model or slicer, not the machine.

How do I know if my filament is wet?

Listen and look. Wet filament pops or hisses at the nozzle, produces a rough bubbly surface, and strings heavily. PETG, TPU, nylon, and PVA absorb moisture fastest. Drying at the manufacturer’s recommended temperature for four to six hours usually restores it.

Bottom line

Change one variable at a time, in the order below, and write down what you changed. Most "bad printer" complaints are a dirty plate and damp filament. For model-by-model comparisons and current pricing, use our main guide: Compare our 3D printer picks.