Under-extrusion occurs when the printer deposits less filament than expected, resulting in gaps between layers, thin or missing walls, and weak prints with visible holes in the surface.
Common Causes
- Incorrect flow rate — The extrusion multiplier or flow rate is set too low
- Partially clogged nozzle — Debris or degraded filament restricts flow
- Filament diameter inconsistency — Actual filament diameter differs from slicer settings
- Extruder gear slipping — The drive gear cannot grip the filament properly
- Print speed too high — The extruder motor cannot keep up with the demanded feed rate
- Low nozzle temperature — Insufficient heat makes filament harder to push through
Recommended Fixes
- Calibrate your extruder steps/mm (e-steps) using a measured extrusion test
- Clean or replace the nozzle to remove any partial blockages
- Measure filament diameter with calipers and update your slicer profile
- Check the extruder gear tension and replace worn drive gears
- Reduce print speed by 10-20% and observe if gaps disappear
- Increase nozzle temperature in 5°C increments until flow is consistent
- Replace worn or low-quality PTFE tubing in Bowden setups