Over-extrusion: more material comes out than needed

Likely causes

In order: the most frequent cause comes first.

1. 01Extrusion multiplier or flow rate set above the real value
2. 02Wrong filament diameter declared in the slicer (1.75 when the real one is 1.70, for instance)
3. 03Temperature too high, making the material swell as it exits
4. 04Badly calibrated extruder steps per millimetre
5. 05Extrusion width set above what the nozzle can lay down cleanly

How to fix it

Apply one fix at a time and reprint the same test part. Changing three settings at once tells you nothing about which one worked.

1. 01

   Calibrate flow with a single-wall cube

   Medium

   Print a hollow single-wall cube with zero infill and measure the wall thickness with callipers at several points. If it measures more than the configured extrusion width, lower the flow multiplier by the corresponding ratio. OrcaSlicer has this test built in.

2. 02

   Measure the filament's real diameter

   Easy

   With callipers, measure the filament at ten points spread over a metre and average them. Enter that value in the slicer instead of the nominal one. With a ±0.05 mm tolerance, the difference in extruded volume can reach 6 %.

3. 03

   Lower the temperature and review extrusion width

   Easy

   Drop 5 to 10 °C and check whether the walls slim down. Also check that the extrusion width does not exceed roughly 1.2 times the nozzle diameter: with a 0.4 mm nozzle, anything over 0.48 mm starts to hurt the finish.

How to prevent it

• —Calibrate flow once per filament brand and save it in the profile
• —Print a tolerance test part before printing something that has to fit
• —Do not trust the nominal diameter of cheap filament: measure it
• —Keep one profile per material rather than tweaking on the fly

Sources

1. [1]Print Quality Troubleshooting | Prusa Knowledge BasePrusa Research · Manufacturer · accessed July 27, 2026