Repair Fact #6: Filament Jams — When the Flow Says 'No'

"If your extruder clicks like a Geiger counter near Chernobyl — it's jam time."

What Is a Filament Jam?

A filament jam occurs when your printer’s hotend or extruder can’t push filament through the nozzle properly. It can be partial (under-extrusion, clicking) or total (no extrusion at all).

Common Symptoms

Symptom	Likely Cause
Clicking sounds	Back pressure, clogged nozzle
No filament comes out	Total jam, heat creep
Under-extrusion	Partial clog, tension issue
Filament grinding	Gear slipping, hard filament
Extruder motor skips	Obstruction, wrong tension

What Causes It?

Cold extrusion attempts
Incorrect retraction settings
Low-quality or wet filament
Clogged or partially blocked nozzles
Overtightened extruder gears
Heat creep (especially with PLA in all-metal hotends)

How to Fix a Jam

1. Cold Pull (a.k.a. Nylon Trick)

Heat up to 200–220°C
Insert filament, push through
Cool to ~90°C
Yank quickly — this pulls out the clog

2. Unload & Inspect

Remove filament
Check for melted tip or grinding marks
Cut off damaged filament end

3. Clean Nozzle

Use needle or cleaning filament
Consider replacing nozzles every few hundred hours

4. Check Extruder Path

Open the extruder and look for filament debris or tension issues
Make sure gears are clean and gripping properly

5. Replace Low-Quality Filament

Moisture, inconsistent diameter = jam city
Dry filament before use (especially PETG, Nylon)

Prevention Tips

Action	Why It Helps
Dry your filament	Removes moisture-induced clogs
Use proper retraction	Prevents melted blob buildup
Clean nozzle regularly	Prevents partial blockages
Monitor filament quality	Cheap filament = expensive headaches
Lubricate PTFE tubes	Reduces friction in bowden setups

Bonus: G-code Tip to Prevent Jams

Add a gentle filament prime and slow start:

G92 E0
G1 E2 F150 ; extrude slowly to avoid sudden pressure

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