Scarring / Nozzle Marks
Scratches or drag marks on top surfaces from the nozzle dragging across already-deposited material during travel moves.
What It Is
Scratches or drag marks on top surfaces from the nozzle dragging across already-deposited material during travel moves.
How It Forms
During non-print travel moves, the nozzle crosses over previously printed areas. If the nozzle is at the same Z height as the top of the printed material (or lower due to over-extrusion), it physically scrapes across the surface.
The scraping creates visible marks — shiny lines on matte filament, or grooves in the surface. On flexible materials, it can even shift or deform the printed geometry.
Z-hop (raising the nozzle during travel) prevents this by lifting the nozzle above the surface. But Z-hop adds print time and can cause its own artifacts (stringing from the vertical retraction).
Visual Signature
- Lines/scratches that don’t follow the print pattern
- Shiny drag marks on matte surfaces
- More visible on top surfaces and flat areas
- Pattern follows travel move paths (diagonal lines)
Root Causes
| Cause | Calibration Variable | Direction |
|---|---|---|
| Z-hop not enabled | — (slicer) | — |
| Over-extrusion (material sits high) | Flow Rate, E-Steps | ↑ |
| Combing disabled (travels cross print) | — (slicer) | — |
How the Auto-Tuner Detects It
- Camera: Surface marks that don’t align with extrusion pattern
How the Auto-Tuner Fixes It
- Detection only — primarily a slicer setting (enable Z-hop, combing). Auto-tuner can flag over-extrusion as a contributing cause.