Troubleshooting
Why is my 3D print failing? Eight symptoms, in fix order
Almost every failed print is one of eight things, and the order you check them in matters: start with the free fixes (clean the bed, dry the spool) before the ones that need a hex key. Below, each symptom with the first thing to check and the second.
The eight, at a glance
| Symptom | Check first | Then |
|---|---|---|
| corners lifting off the bed | Bed temperature and the first layer | Drafts and cooling |
| hairs between separate parts | Nozzle temperature | Retraction distance and speed |
| one band of the print offset sideways | Belt tension and grub screws | Speed and acceleration |
| extrusion stops mid-print | Heat creep and filament debris | Nozzle and PTFE tube |
| gaps, weak walls, thin lines | E-steps and flow calibration | Partial clog |
| the model sags where support should hold it | Support Z distance | Support density and interface |
| the print detaches on layer one | Bed cleanliness | Z offset and bed levelling |
| holes too small, part 0.2 mm oversize | Shrinkage allowance | Belt calibration and flow |
In detail
warping
What you see: Bed 5–10 °C too cold, or the part cools unevenly on a cool plate.. Check first: bed temperature and the first layer. Then: drafts and cooling.
stringing
What you see: Too hot, or wet filament popping. Dry the spool before changing retraction.. Check first: nozzle temperature. Then: retraction distance and speed.
layer shift
What you see: A slipping belt or a loose pulley. Also check that the part did not get knocked.. Check first: belt tension and grub screws. Then: speed and acceleration.
clogging
What you see: Too much retraction pulling molten plastic up, or dust on the spool.. Check first: heat creep and filament debris. Then: nozzle and ptfe tube.
under-extrusion
What you see: The extruder is asked for more plastic than the hotend can melt.. Check first: e-steps and flow calibration. Then: partial clog.
collapsed supports
What you see: Support fused to the part, or the nozzle knocked it over.. Check first: support z distance. Then: support density and interface.
first layer not sticking
What you see: Grease from fingers is the most common cause, not chemistry.. Check first: bed cleanliness. Then: z offset and bed levelling.
wrong dimensions
What you see: Every material shrinks as it cools; ABS more than PLA.. Check first: shrinkage allowance. Then: belt calibration and flow.
The order that saves the most time
Work the list in this sequence and you will not change three settings to fix one problem. First, the model: a non-manifold mesh slices into something the printer cannot build, and no amount of tuning fixes it — run it through the STL checker before anything else. Second, the filament: moisture causes stringing, popping, under-extrusion and weak walls at once, so a dry spool removes four symptoms from the list. Third, the bed: cleanliness, then levelling, then Z offset. Fourth, and only then, the slicer: temperature, retraction, flow and speed.
Change one thing at a time and keep the failed part. A workshop that keeps its failures can compare the layer where the print went wrong with the settings that produced it; a workshop that throws them away re-learns the same lesson every month.
When it is the material's fault
PETG strings when it is wet and ABS warps when it cools too fast — those are properties, not misconfigurations. If you are choosing between them, the PETG vs ABS comparison covers heat, strength, smell and enclosure requirements. If you are losing a fifth of your prints, failure rates puts a price on each point, and filament usage shows how to allow for the ones you will lose. What a failed print does to your cost per gram is on the per-gram page.
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Frequently asked questions
Why do my 3D prints keep failing?
Most failures come from four places, in this order of likelihood: a dirty or badly levelled bed, wet filament, a non-manifold model, and slicer settings that ask for more flow than the hotend can deliver. Fix them in that order and most prints start succeeding without touching the profile.
What is the most common cause of a failed first layer?
Grease on the build plate. Fingerprints are enough to stop PLA sticking. Wash the sheet with dish soap and warm water, dry it, and re-check the Z offset before changing any temperature.
Is stringing a sign of wet filament?
Often, yes. Moisture turns to steam in the nozzle and pushes plastic out during travel. Dry the spool at the manufacturer's temperature for four to six hours and re-test before touching retraction settings.