Over Extrusion vs. Under Extrusion

Over-extrusion in 3D printing is generally easier to detect with the naked eye than under-extrusion. When too much filament is extruded, you often see obvious signs like blobs, stringing, or excessively thick layers where the filament appears to spill or ooze beyond the intended boundaries. These visual cues—such as raised ridges between surface lines or drooping layers caused by excess material—make over-extrusion relatively straightforward to identify. The surface of the print may look messy or oversized, which indicates that the printer is pushing out more material than necessary.

In contrast, under-extrusion can be subtler visually but can have a more serious impact on print strength. Even if an under-extruded part looks acceptable on the surface, missing or thin filament deposition means the layers are not fully bonded, and the internal structure can be fragile. This results in prints that crumble, crack, or tear more easily under stress, since insufficient filament compromises the object's mechanical integrity. Gaps between layers or sparse infill may not always be immediately apparent, but they weaken the part significantly. So while under-extrusion can be harder to spot at a glance than over-extrusion, it poses a greater risk to the durability and functionality of the final print. Monitoring print quality with attention to detail is necessary to avoid these hidden weaknesses.

This means visual inspection alone might not detect under-extrusion sufficiently, making calibration and careful tuning essential for strong, reliable 3D prints. Over-extrusion errors warn you visually that something is wrong, but under-extrusion can quietly degrade part quality even if it looks good initially.