Troubleshooting Common 3D Print Problems
Stringing, warping, layer separation, clogs, and more — a practical guide to diagnosing and fixing the most common FDM 3D printing failures.
Something went wrong with your print. Here's how to diagnose and fix the most common issues in FDM (fused deposition modeling) printing.
Stringing (Fine Hairs Between Parts)
What it looks like: Thin threads of plastic stretching across open spaces between parts of your print — like a spider web.
Causes and fixes:
| Cause | Fix |
|---|---|
| Temperature too high | Lower nozzle temp by 5°C increments |
| Retraction too low | Increase retraction distance by 0.5mm |
| Travel speed too slow | Increase travel speed (150–200 mm/s) |
| Wet filament | Dry your filament (70°C for 6–8 hours) |
PETG note: PETG strings more than PLA by nature. Expect some stringing and use a heat gun or lighter to remove the hairs post-print.
Warping (Corners Lifting Off the Bed)
What it looks like: Corners or edges of the print peel off the bed during or after printing, sometimes causing the entire print to detach.
Causes and fixes:
| Cause | Fix |
|---|---|
| Bed too cold | Increase bed temperature |
| No enclosure (ABS/ASA) | Print in an enclosure or add a draft shield in slicer |
| Poor bed adhesion | Clean bed with IPA; use glue stick or hairspray |
| Cooling fan too aggressive | Reduce fan speed, especially for first layers |
| Ambient drafts | Block airflow around printer |
Prevention: Use a brim (extra skirt around the base) or raft in your slicer settings. This increases the surface area contacting the bed.
Layer Separation / Delamination
What it looks like: Layers splitting apart, especially on tall prints or at stress points.
Causes and fixes:
| Cause | Fix |
|---|---|
| Temperature too low | Increase nozzle temp by 5°C |
| Print speed too fast | Reduce print speed |
| Layer height too tall | Reduce layer height (max 75% of nozzle diameter) |
| Drafts cooling the print | Reduce cooling fan; add enclosure |
| Wet filament | Dry filament before printing |
Under-Extrusion (Gaps, Weak Prints, Missing Lines)
What it looks like: Lines in your print are incomplete, the surface has holes, or layers are visibly weak and gappy.
Causes and fixes:
| Cause | Fix |
|---|---|
| Temperature too low | Raise nozzle temp |
| Print speed too fast | Slow down |
| Partial clog | Do a cold pull (see below) |
| Filament diameter wrong | Check slicer filament diameter setting (1.75mm vs 2.85mm) |
| Extruder slipping | Check extruder tension; clean drive gear |
Cold pull technique: Heat nozzle to print temp, push filament through manually, then cool to ~90°C and pull firmly. This drags any debris with it. Repeat until the pulled filament tip comes out clean.
Over-Extrusion (Blobs, Zits, Rough Surfaces)
What it looks like: Too much plastic — rough surfaces, blobs where the nozzle starts or stops, lines are thicker than expected.
Causes and fixes:
| Cause | Fix |
|---|---|
| Flow rate too high | Reduce flow/extrusion multiplier by 5% in slicer |
| Temperature too high | Lower nozzle temp |
| Retraction insufficient | Increase retraction |
| Pressure advance not calibrated | Calibrate pressure advance (Klipper) or linear advance (Marlin) |
First Layer Not Sticking
What it looks like: Filament curls up behind the nozzle instead of adhering, or the first layer peels off immediately.
Causes and fixes:
| Cause | Fix |
|---|---|
| Nozzle too far from bed | Re-level bed; decrease Z offset (move nozzle closer) |
| Bed not clean | Wipe with 99% isopropyl alcohol |
| Bed too cold | Raise bed temperature |
| First layer speed too fast | Slow first layer to 15–25 mm/s |
| Wrong bed surface for material | PEI for most; glass + glue for PETG |
Nozzle Clog
What it looks like: No filament coming out, or severely reduced flow. Often happens after printing at too-low temperatures or switching materials.
Fixes (in order of intensity):
- Heat and manual push: Heat to print temp and push filament by hand firmly for 30 seconds.
- Cold pull: Heat to 200°C, push filament, cool to 90°C, pull hard. Repeat.
- Increase temp: Heat to 260°C (if your hotend supports it) and push through.
- Acupuncture needle: Use a 0.3mm cleaning needle from the outside.
- Replace nozzle: Nozzles are inexpensive and sometimes easier to replace than clean.
Spaghetti (Print Collapses Mid-Way)
What it looks like: At some point during printing, the layers stop adhering and the extruded filament just hangs in the air, creating a tangled mess.
Causes:
- Poor bed adhesion — the print detached and the nozzle started printing in the air
- A knock or vibration dislodged the print
- Support failure on an overhanging section
Fix: Address the root cause (usually bed adhesion or adding supports) and start over. There's no recovering a spaghetti print.
Elephant's Foot (Flared Base)
What it looks like: The bottom few layers are wider than they should be, creating a visible flare.
Causes and fixes:
| Cause | Fix |
|---|---|
| Nozzle too close to bed | Increase Z offset slightly |
| Bed too hot | Lower bed temperature by 5°C |
| First layer squish too high | Reduce first layer flow rate |
When in Doubt: The Checklist
Work through this before giving up:
- Is your filament dry? Wet filament causes 80% of mysterious print problems.
- Is your bed level and clean?
- Is your temperature in the right range for your material?
- Is your print speed reasonable?
- Do you have the right retraction settings for direct drive vs Bowden?
Find verified starting-point settings for your specific printer and filament in our Settings database.