Under Extrusion

In 3D printing, the software calculates how much plastic the printer should extrude, but the printer itself doesn’t provide feedback on the actual amount of filament that leaves the nozzle. This can lead to a situation where less plastic is extruded than expected—commonly known as under-extrusion. When this happens, you may notice gaps between the lines of plastic within each layer.

Printing a 20mm tall cube with at least 3 perimeter outlines is a simple way to check for under-extrusion. Examine the top of the cube: if the perimeters have noticeable gaps between them, your printer is likely under-extruding. The issue may lie elsewhere if the perimeters are tightly bonded with no gaps. If under-extrusion is confirmed, here are some common causes and solutions.

Common Causes and Solutions:

Incorrect Filament Diameter

The first thing to check is whether the software is set to the correct filament diameter. Most filaments have a diameter of either 1.75mm or 2.85mm, and this information is generally printed on the filament packaging. You can measure the filament with callipers to ensure accuracy if in doubt.

Increase the Extrusion Multiplier

If the filament diameter is correct but you’re still experiencing under-extrusion, adjusting the extrusion multiplier may help. This setting controls the amount of extruded filament, often called the "flow rate". If your printer has multiple extruders, ensure you adjust the correct one.