Common 3D Printing Mistakes and How to Fix Them
Even with a perfect CAD model, a bad print can ruin the result. Here are the most common FDM 3D printing problems: what causes them and how to fix them.
Stringing
What it looks like: Thin spider-web strands of plastic between parts of the print.
Cause: Molten plastic oozing from the nozzle as it travels between features.
Fix:
- Increase retraction distance (1–6mm for direct drive, 4–7mm for Bowden)
- Increase retraction speed (40–60mm/s)
- Reduce print temperature by 5°C increments
- Enable "Avoid crossing perimeters" in your slicer
Layer Separation (Delamination)
What it looks like: The print splits between layers: horizontal cracks.
Cause: Insufficient layer bonding, usually from too-low temperature, too-fast printing, or too-large layer height.
Fix:
- Increase print temperature by 5°C
- Reduce print speed
- Reduce layer height to 0.2mm or less
- Check for drafts (enclosure helps)
Warping
What it looks like: Corners lifting off the print bed during printing.
Cause: Thermal contraction of the cooling plastic pulling edges upward.
Fix:
- Increase bed temperature (60°C for PLA, 80°C for PETG, 100–110°C for ABS)
- Add a brim (3–8mm) in your slicer to anchor corners
- Print in an enclosure for ABS/ASA
- Clean the bed with IPA before printing
- In CAD, add a raft or chamfer the bottom edges of your model
Elephant Foot
What it looks like: The first few layers are wider than the rest, creating a flared base.
Cause: Too much bed adhesion squishing the first layer, or too-high bed temperature.
Fix:
- Increase the Z offset (move nozzle slightly higher from bed)
- Reduce first-layer flow rate to 95%
- Reduce bed temperature slightly
- In FreeTextToCAD, prompt for a small 45° chamfer on the base to compensate
Under-Extrusion
What it looks like: Gaps between lines, inconsistent walls, weak layers.
Cause: The extruder isn't pushing enough filament. Often caused by a partial clog, worn Bowden tube, or incorrect flow rate.
Fix:
- Run a cold pull to clear partial clogs
- Calibrate your extruder steps (e-steps)
- Increase print temperature by 5°C
- Increase flow rate to 105%
- Check for Bowden tube wear at the hot end connection
Supports Won't Come Off
What it looks like: Support material fused to the part, tearing chunks when removed.
Cause: Interface layer too close to part surface, or no interface layer used.
Fix:
- Enable support interface layers at 0.2mm gap
- Reduce interface layer flow to 90%
- Use a different interface material (e.g., PVA or HIPS with dual extrusion)
- Re-design the model to eliminate supports: see our guide on overhangs