Clogging / Partial Clog
Nozzle fully or partially blocked. No extrusion (full clog) or reduced, inconsistent extrusion (partial clog).
What It Is
Nozzle fully or partially blocked. No extrusion (full clog) or reduced, inconsistent extrusion (partial clog).
How It Forms
Several mechanisms:
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Carbonization — Filament left at high temperature too long burns and carbonizes. The carbon deposits narrow the nozzle opening or create a plug. Common when heating the nozzle and leaving it idle.
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Foreign particles — Dust, debris, or low-quality filament with contaminants gets pushed into the nozzle. Particles too large for the nozzle opening lodge at the tip.
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Heat creep jam — Softened filament in the cold zone solidifies into a plug when the printer cools down. On next heat-up, the plug doesn’t fully re-melt.
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Filament change remnants — When switching filaments, the old material may not fully purge. If the new filament has a different melt temp, remnants of the old can solidify and partially block the path.
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Nozzle wear — Abrasive filaments (carbon fiber, glow-in-the-dark, metal-fill) erode brass nozzles. The eroded particles can partially block the path or the deformed nozzle geometry creates turbulent flow.
Visual Signature
- Sudden complete stop of extrusion (full clog)
- Inconsistent, sputtering flow (partial clog)
- Extruder clicking/grinding (motor can’t push through)
- Thin, irregular lines that vary in width
- Extrusion works briefly after clearing, then clogs again (recurring)
Root Causes
| Cause | Calibration Variable | Direction |
|---|---|---|
| Temperature too high for too long | Extrusion Temp | ↑↑ |
| Cheap filament with contaminants | — (material quality) | — |
| Heat creep (see heat-creep.md) | Extrusion Temp, Retraction | — |
| Incomplete filament purge | — (procedure) | — |
| Nozzle wear from abrasive filament | — (hardware) | — |
How the Auto-Tuner Detects It
- Roller encoder: Commanded movement with no actual movement = full clog. Commanded vs. actual diverging = partial clog.
- Extruder current (future): Motor draws more current when pushing against a blockage.
How the Auto-Tuner Fixes It
- Detection: Immediate pause when encoder detects no flow. Prevents grinding.
- Prevention: Temperature management, filament quality monitoring.
- Clearing: Cannot clear a clog automatically — but detecting it early prevents the cascading damage of continued grinding.