Over-extrusion
Too much material deposited — excess plastic has nowhere to go, so it bulges outward, upward, or accumulates on the nozzle.
Medium severity
Extrusion
What It Is
Too much material deposited — excess plastic has nowhere to go, so it bulges outward, upward, or accumulates on the nozzle.
How It Forms
More filament is pushed through the nozzle than the toolpath geometry can accommodate. The excess material:
- Bulges outward — Walls become wider than designed, parts are dimensionally oversized
- Pushes upward — Creates bumps and rough surfaces as excess stacks on previous layers
- Accumulates on the nozzle — Molten plastic curls back up around the nozzle tip, eventually falling as blobs
On first layers, over-extrusion is amplified because the nozzle squishes excess material against the bed — this is how elephant foot forms.
Visual Signature
- Rough, bumpy surfaces
- Dimensional inaccuracy (parts too large)
- Elephant foot on first layers
- Filament curling around nozzle tip
- Blobs and raised seam lines
- Hard to insert parts into designed holes
Root Causes
| Cause | Calibration Variable | Direction |
|---|---|---|
| E-steps too high | E-Steps | ↑ |
| Flow multiplier too high | Flow Rate | ↑ |
| Temperature too hot | Extrusion Temp | ↑ |
| Nozzle too close to bed | Z-Offset | ↓ (too close) |
| Filament diameter larger than slicer expects | Flow Rate | effective ↑ |
How the Auto-Tuner Detects It
- Roller encoder: Actual filament movement matches commanded but walls are too thick → flow calibration needed
- Camera: Surface roughness analysis, dimensional comparison to model
How the Auto-Tuner Fixes It
- Calibration: Correct E-steps, reduce flow multiplier, lower temperature
- Live tuning: Encoder monitors that commanded and actual match — if they do and walls are still thick, it’s a flow multiplier issue flagged for recalibration