Common FDM Print Issues and How to Fix Them
Even with a perfectly set up printer and good slicing settings, FDM prints can fail due to various issues. Problems like warping, under-extrusion, or stringing can ruin prints and waste time and filament.
This guide will help you:
✅ Identify the most common FDM printing problems
✅ Understand the causes behind them
✅ Apply quick and effective solutions
By the end, you’ll know how to troubleshoot your prints and get consistently better results!
1. Poor Bed Adhesion: Print Not Sticking to the Bed
If your print doesn’t stick or detaches mid-print, it can lead to failed prints.
🔹 Causes:
❌ Bed not level or too far from the nozzle.
❌ Dirty print surface (dust, oil, or residue).
❌ Incorrect bed temperature.
✅ Fixes:
✔ Re-level the bed – Adjust the screws or use auto-bed leveling.
✔ Clean the print surface – Use isopropyl alcohol (IPA) to remove grease.
✔ Increase first layer temperature – Helps filament adhere better.
✔ Use adhesion helpers – A brim, raft, or glue stick can improve first-layer bonding.
💡 Tip: Lower your first layer print speed (20-30mm/s) for better adhesion.
2. Warping: Corners Lifting Off the Bed
Warping happens when the edges of your print curl up, often ruining the print.
🔹 Causes:
❌ Bed too cold (especially for ABS, PETG).
❌ Sudden cooling (causing uneven contraction).
❌ First layer not sticking well.
✅ Fixes:
✔ Use a heated bed – 60°C for PLA, 80°C for PETG, 100°C for ABS.
✔ Reduce cooling for the first few layers – Keeps adhesion strong.
✔ Apply a brim or raft – Extra surface area helps prevent curling.
✔ Use an enclosure – Traps heat and reduces temperature changes.
💡 Tip: ABS warps a lot—print in a warm room or use an enclosure.
3. Stringing (Thin Plastic Hairs Between Parts)
Stringing happens when filament oozes between travel moves, creating thin plastic strands.
🔹 Causes:
❌ Retraction settings not optimized.
❌ Print temperature too high (filament too runny).
❌ Travel speed too slow.
✅ Fixes:
✔ Enable retraction – Start with 5mm at 40mm/s (Bowden) or 1.5mm at 35mm/s (Direct Drive).
✔ Lower print temperature – Reduce by 5-10°C and test.
✔ Increase travel speed – Set to 150-200mm/s to reduce filament drips.
💡 Tip: Run a stringing test to fine-tune retraction settings.
4. Under-Extrusion (Gaps in Layers or Weak Prints)
If your print has gaps, missing layers, or weak walls, your printer is not extruding enough filament.
🔹 Causes:
❌ Nozzle partially clogged.
❌ Extruder not pushing filament correctly.
❌ Low flow rate or printing too fast.
✅ Fixes:
✔ Clean the nozzle – Use a cleaning needle or cold pull method.
✔ Check extruder gears – Make sure filament is feeding correctly.
✔ Increase flow rate (Extrusion Multiplier) – Try 105-110% in slicer.
✔ Slow down print speed – Helps ensure consistent extrusion.
💡 Tip: If printing grindy noises occur, check for filament grinding in the extruder gears.
5. Over-Extrusion (Too Much Filament, Blobs, and Elephant’s Foot)
Over-extrusion results in thick layers, blobs, or bulging at the bottom (elephant’s foot).
🔹 Causes:
❌ Flow rate too high.
❌ Nozzle too close to the bed.
❌ First layer temp too high.
✅ Fixes:
✔ Reduce flow rate – Start at 95% and adjust as needed.
✔ Re-level the bed – Ensure the nozzle is not pressing too hard.
✔ Lower first layer temp – Helps prevent bottom layers from over-expanding.
💡 Tip: Use draft shield or ooze shield to catch excess filament before it affects the print.
6. Layer Shifting (Print Looks Misaligned)
If your print suddenly shifts layers, it’s usually caused by mechanical issues.
🔹 Causes:
❌ Loose belts or stepper motor skipping.
❌ Printer moving too fast.
❌ Print head hitting the model.
✅ Fixes:
✔ Tighten the belts – A loose belt can cause shifts.
✔ Slow down print speed – Try 50-60mm/s for better accuracy.
✔ Check for obstructions – Make sure the print head isn’t hitting curled-up parts.
💡 Tip: Add Z-hop (0.2-0.5mm) to prevent the nozzle from knocking over prints.
7. Clogged Nozzle (Filament Won’t Extrude Properly)
A clogged nozzle prevents smooth extrusion and can cause under-extrusion or missing layers.
🔹 Causes:
❌ Dirt or debris in the nozzle.
❌ Printing at low temperature.
❌ Old filament degrading in the nozzle.
✅ Fixes:
✔ Heat up the nozzle and manually extrude filament.
✔ Use a nozzle cleaning needle to remove debris.
✔ Perform a cold pull – Heat filament to 200°C, push it in, cool to 90°C, then pull it out.
✔ Replace the nozzle if cleaning doesn’t work.
💡 Tip: Use high-quality filament to prevent dust and debris buildup inside the nozzle.
8. Brittle or Weak Prints
If your print breaks too easily, it may be caused by incorrect material settings.
🔹 Causes:
❌ Too little infill or wall thickness.
❌ Too low nozzle temperature (weak layer bonding).
❌ Cooling fan too strong.
✅ Fixes:
✔ Increase wall thickness (1.2mm minimum).
✔ Increase infill to at least 20-30%.
✔ Raise the print temperature by 5-10°C.
✔ Reduce cooling for stronger layer adhesion.
💡 Tip: PETG is stronger than PLA—if you need durability, try switching materials.
9. Overheating & Poor Cooling (Blurry or Melting Details)
If prints look melted or droopy, the filament isn’t cooling fast enough.
🔹 Causes:
❌ Printing too hot.
❌ Poor cooling fan setup.
❌ Too slow print speed.
✅ Fixes:
✔ Lower nozzle temp by 5-10°C.
✔ Increase part cooling fan speed (100% for PLA, 50% for PETG).
✔ Enable “minimum layer time” in slicer to slow small layers.
💡 Tip: For tiny prints, print multiple copies at once to allow more cooling time.
Conclusion: Troubleshooting Like a Pro
3D printing isn’t just about hitting “print”—small adjustments can drastically improve quality. By understanding common problems and solutions, you’ll reduce failed prints and get consistent, high-quality results.
✅ Bed adhesion and leveling are key!
✅ Optimize extrusion to prevent under/over-extrusion issues.
✅ Cooling, speed, and support settings affect print quality.
Now that you’ve completed this beginner’s guide, you’re ready to confidently print, troubleshoot, and improve your FDM printing skills!
Adeptus Printicus 
Leave a comment