Under-extrusion: when too little material reaches the print
Under-extrusion means less plastic leaves the nozzle than the toolpath requires. The result can be gaps, thin lines, weak walls and incomplete layers. The cause may be the filament, hotend, extruder or slicer profile.
Typical signs
- gaps between extrusion lines
- thin or interrupted perimeters
- weak top surfaces
- extruder clicking
- unusually light and fragile part
- partially missing layers
Check filament feed
Check whether:
- the spool turns freely
- filament is not tangled
- the feed path is unobstructed
- filament is dry
- the correct filament diameter is configured
Check the nozzle
A partial clog can reduce flow. If the extruder also clicks or grinds filament, inspect the nozzle and hotend according to the printer manufacturer's instructions.
Check temperature
A nozzle temperature that is too low can limit volumetric flow, especially with high speed, wide extrusion, large layer heights or larger nozzles.
- high speed
- wide extrusion
- large layer heights
- larger nozzles
Check the extruder
Possible issues:
- idler pressure
- dirty drive gears
- filament dust
- gearbox or feeder alignment
Do not over-squish the first layer
A nozzle that is too close to the bed can restrict extrusion.
Do not use flow as the first repair
If a previously working profile suddenly under-extrudes, check mechanical and material causes before making a large flow adjustment.