How to Fix Under-Extrusion in 3D Printing
Visible gaps between extrusion lines, thin or missing walls, and a generally weak or patchy-looking print surface.
Common causes
Partially clogged nozzle
Debris or burnt filament residue restricts how much plastic can flow through.
Worn or loose extruder gripping
If the extruder's gear isn't gripping the filament firmly, it can't push consistently.
Wrong filament diameter setting
If the slicer thinks your filament is a different diameter than it actually is, it under-calculates how much to extrude.
Nozzle temperature too low
Plastic that isn't fully molten flows more slowly than the print speed demands.
Print speed faster than the hot end can keep up with
Every hot end has a maximum flow rate — pushing past it causes under-extrusion regardless of temperature.
How to fix it
Do a cold pull
This clears debris from the nozzle and is the standard first step whenever flow seems restricted.
Check extruder tension
Increase the idler tension slightly if you see the filament slipping or grinding against the drive gear.
Measure your filament with calipers
Update the slicer's filament diameter setting to match what you actually measure, not just the spool label.
Raise the nozzle temperature
In small increments, until flow keeps up consistently with your print speed.
Slow down the print
If temperature increases alone don't fix it, the hot end may simply need more time per millimeter of filament.
Still stuck?
ForgePrint diagnoses the exact cause for your printer and filament — describe it, or just upload a photo.