Überextrusion

Überextrusion, also known as over-extrusion, is a defect in additive manufacturing, particularly in fused deposition modeling (FDM), where more filament is extruded than required for the intended geometry. The excess material can widen perimeters, fill gaps that should remain visible, and cause raised, rounded edges and thicker layers. Parts may have dimensional inaccuracies, rough surfaces, or blobby protrusions at corners and junctions.

Causes include a miscalibrated extrusion multiplier or flow rate, which tells the printer how much filament to push. Related factors are incorrect filament diameter input in the slicer, filament variability, and temperatures that are too high for the material. Extrusion width set above the nozzle size or inconsistent feed can also contribute. Mechanical issues such as minor pressure buildup in the melt path or imperfect retraction can exacerbate the effect, though they are more commonly linked to other extrusion problems.

Symptoms and effects often appear as widened lines on outer perimeters, filled gaps beyond the intended geometry, and visibly thicker layers. Surface quality suffers, edges become rounded, and there is higher material usage and potential interference with fit between parts.

Diagnosis and correction involve calibrating the extrusion multiplier (or flow) and accurately measuring filament diameter. Print a calibration cube or line test, compare actual dimensions to targets, and adjust E-steps per millimeter or slicer settings accordingly. If needed, reduce the printing temperature slightly, lower the print speed, or adjust extrusion width to better match the nozzle. Ensuring a clean nozzle and smooth filament feed also helps stabilize extrusion.