Clogged nozzle: how to unclog a 3D printer nozzle
A clogged nozzle is a blockage in the nozzle or hotend that stops filament flowing, usually burnt residue, dust or debris. Most partial clogs clear with a cold pull: push PLA through the hot nozzle, let it cool to about 85–100 °C, then pull it out with the dirt attached. If two or three pulls don't work, replace the nozzle. It's a cheap consumable, not a lifetime part.
- Rule out look-alikes: nozzle too close to the bed, a tangled spool, a slipping extruder, or heat creep.
- Heat to the last material's printing temperature and push filament through by hand. Watch what comes out.
- Do a cold pull with light-coloured PLA, pulling at 85–100 °C. Repeat until the tip comes out clean.
- Tip still blocked? At printing temperature, clear it from below with the cleaning needle from your printer kit (standard nozzles only).
- Still clogged after 2–3 tries? Replace the nozzle, or the hotend assembly on quick-swap printers.
Is it a clog? Rule out the look-alikes
Plenty of problems look like a clog but aren't. Check these before you take anything apart:
| What you see | Likely cause | First check |
|---|---|---|
| Nothing comes out on the first layer, but it extrudes fine in mid-air | Nozzle too close to the bed | Raise the Z-offset; see first layer not sticking |
| No or weak extrusion at temperature; extruder clicks | Full or partial clog | Push filament by hand at temperature; if it won't flow, cold pull |
| Starts fine, stops mid-print with no error; swollen filament end | Heat creep | Hotend fan and heatsink; see heat creep |
| Fine when slow, gaps and clicking when fast | Hotend can't melt fast enough | Lower speed or max volumetric speed |
| Gears spin, filament doesn't move, plastic dust in the extruder | Ground-down filament | Clean the gears, check idler tension, then look for a clog |
| Popping or hissing, rough surfaces | Wet filament | Dry the spool |
| Black or brown specks in prints | Burnt residue inside the nozzle | Cold pull |
| Filament stops feeding, spool is hard to turn | Tangled spool or snagged path | Unwind and check the feed path |
How to do a cold pull (atomic pull)
A cold pull uses a plug of plastic to drag residue out of the nozzle. It works when at least some filament still comes out. Prusa's testing found PLA works best because it holds the shape of the nozzle without tearing; a light colour shows dirt clearly. Prusa CORE One printers, and MK4/S and MK3.9/S printers on firmware 6.0 or later, can do this automatically from LCD Menu → Control → Cold Pull.
- Unload the current filament. If it was a hotter material (PETG, ABS, nylon), purge with PLA at that material's temperature first.
- Heat the nozzle to 235–270 °C. Prusa uses 270 °C and UltiMaker 235 °C. On a PTFE-lined hotend, stay at or below about 240 °C.
- Push a straight 20–30 cm piece of PLA in by hand until it flows from the nozzle. On Bowden printers, disconnect the tube at the hotend; on direct drive, open the idler.
- Turn the heater off or set the pull temperature, and keep light downward pressure while it cools so no air gap forms.
- At 85–100 °C, pull straight up with a firm, steady pull. Pliers protect your hand if it snaps.
- Inspect the tip. A clean cone the shape of the nozzle means you're done. Dark residue means cut the tip off and repeat.
| Pull with | Heat to | Pull at | Notes |
|---|---|---|---|
| PLA | 235–270 °C | 85–100 °C | Prusa: 85 °C on MK3, 100 °C on MK4 family, XL and CORE One |
| Cleaning filament | About 260 °C | About 135 °C | UltiMaker's values; follow your pack's instructions |
| ABS or other high-temperature material | Its printing temperature | 140–160 °C | UltiMaker's range for ABS and high-temperature materials |
If the tip snaps off inside, pull 5–10 °C hotter next time. If it stretches into a thin string with no nozzle shape, pull cooler.
Coated nozzles: Prusa says not to cold-pull its non-stick Nozzle X; use cleaning filament only. Check your nozzle maker's advice before cold-pulling any coated nozzle.
Your cold-pulled PLA stretched into a long thin string with no nozzle shape on the end. What should you change?
A stringy, stretched tip means the plastic was still too soft. Let it cool further (toward 85 °C for PLA). If the tip snaps off inside the nozzle instead, it was too cold.
Clear the tip with a cleaning needle
A needle clears a blocked tip; a cold pull clears the inside. Prusa's method: heat the nozzle to the material's printing temperature, then insert the acupuncture needle from the printer's kit (or a 0.3–0.35 mm wire for a 0.4 mm nozzle) from below, about 1–2 cm deep, while pushing filament from above. Pull the needle out and let the filament flush through. Not every maker agrees: E3D advises against needles for its V6 nozzles and recommends cold pulls or nylon cleaning filament instead.
Use a needle a little smaller than the nozzle hole, heat-resistant gloves, and the printer's own heating.
Don't use a needle on high-flow nozzles (Prusa says their internal shape doesn't suit it), and never use a drill bit in a power drill.
How to change a 3D printer nozzle safely
Check your printer's own procedure first. Bambu Lab printers swap the whole hotend as one part. Prusa's Nextruder (MK4 family and CORE One) uses its own nozzle system held by thumb screws. E3D Revo nozzles are hand-tight and can be changed cold. For traditional screw-in nozzles (V6-style and the MK8-style on many Ender 3 printers):
- Heat the hotend to the temperature your hotend maker specifies. E3D hot-tightens brass V6 nozzles at 285 °C; never take a PTFE-lined hotend above about 240 °C.
- Hold the heater block with a spanner so you don't twist the heat break or tug the heater and thermistor wires.
- Unscrew the nozzle with a socket or spanner that fits snugly (usually 6 or 7 mm). Adjustable wrenches round off the flats.
- Screw in the new nozzle by hand, then tighten firmly while hot. E3D specifies 2 N·m for V6 nozzles. That's a small spanner and two fingers, not your whole arm.
- On V6-style hotends, leave a small gap (about 0.5 mm) between the nozzle hex and the heater block, so the nozzle seals against the heat break.
- Re-check the first layer. A new nozzle can sit at a slightly different height. Printers that sense nozzle contact re-measure it themselves.
Burn and fire risk: the nozzle is above 200 °C during this job. Prusa warns never to heat the nozzle with an external source such as a heat gun or torch; use the printer's own heater. Don't leave it hot and unattended, and power off before touching hotend wiring. Afterwards, make sure the thermistor and heater cartridge are fully seated, because a loose thermistor can cause thermal runaway.
Fully jammed: clearing the heat break or replacing the hotend
If nothing moves even at temperature, the jam is probably above the nozzle, in the heat break.
- Heat to the jammed material's printing temperature, open the extruder or remove the PTFE tube, and try pulling the filament out from the top with pliers.
- Still stuck? Remove the nozzle (hot, as above) and push the plug down through the heat break with a fresh piece of filament, or with the pin tool or hex key that came with your printer.
- On PTFE-lined hotends, replace the liner if it's discoloured or deformed. Cut the new one perfectly square and seat it firmly against the nozzle with no gap.
- Replace the heat break or the whole hotend if it still won't clear. On quick-swap printers, fit a spare and clean the old one later.
Brass vs hardened steel: choosing a nozzle
| Nozzle | Use for | Notes |
|---|---|---|
| Brass | PLA, PETG, ABS, ASA, TPU, unfilled nylon | Cheap, best heat transfer, wears quickly on abrasive filament |
| Stainless steel | Non-abrasive filaments | Not for abrasives: Bambu Lab saw visible wear after about 10 h of PETG-CF |
| Hardened steel | Carbon or glass fibre, glow-in-the-dark, wood, marble, metal-filled, sparkle | Bambu Lab's recommendation for abrasives; transfers heat less well than brass, so you may need slightly more temperature or less flow |
| Coated (e.g. Nozzle X) | Less plastic sticking to the tip | Follow the maker's cleaning advice |
| Tungsten carbide, ruby or diamond-tipped | Heavy abrasive use | Very wear-resistant, expensive |
Nozzle sizes: 0.4 mm is the standard. 0.2 mm gives fine detail but clogs easily; Bambu Lab says never to use it with particle-filled filaments. 0.6 mm is Bambu Lab's first choice for abrasive filaments, and it's faster and stronger for functional parts. High-flow nozzles have a longer melt zone for higher max volumetric speed. More on filled materials in the engineering materials guide.
When to replace a nozzle
- Clogs keep coming back after two or three cold pulls.
- The tip is worn: the hole looks oval or larger, or the flat face around it has rounded off. Lines get wider and fine details soften.
- Under-extrusion or rough tops that calibration can't fix.
- After a crash, or if the tip is bent or the threads are damaged.
- A brass nozzle has printed abrasive filament, even for a few hours.
There's no fixed hour count, because wear depends on the material. Prusa suggests considering a new nozzle after 3–6 months of regular use if quality is poor even after maintenance. Keep a spare in the drawer; they cost far less than a day of failed prints.
How to prevent clogs
- Dry hygroscopic filaments (PETG, nylon, TPU, PC) before printing. See the filament drying guide.
- Use hardened steel, ideally 0.6 mm, for abrasive filaments.
- Stay within the hotend's max volumetric speed for each filament.
- Seat PTFE and Bowden tubes firmly with square-cut ends and no gaps.
- Purge or cold pull when switching from a high-temperature material to a lower one; UltiMaker recommends it.
- Don't leave a hot nozzle sitting with filament in it. Keep the firmware's idle timeout enabled.
- Keep filament dust-free and brush ground plastic out of the extruder gears.
Frequently asked questions
How do I unclog a 3D printer nozzle?
Start with a cold pull: heat the nozzle, push a piece of PLA through by hand, let it cool to about 85–100 °C while keeping light pressure on it, then pull it straight out. Residue comes out on the tip. Repeat until the tip is clean. If two or three pulls don't work, replace the nozzle.
What temperature should I use for a cold pull?
With PLA, heat to 235–270 °C (stay at or below about 240 °C on PTFE-lined hotends) and pull at 85–100 °C. Cleaning filament is typically heated to about 260 °C and pulled at about 135 °C. When cleaning out ABS or other high-temperature material, UltiMaker pulls at 140–160 °C.
Do I need a hardened steel nozzle?
Only for abrasive filaments: carbon or glass fibre, glow-in-the-dark, wood, marble, metal-filled and sparkle filaments. For plain PLA, PETG, ABS, ASA and TPU, brass is cheaper and conducts heat better.
How often should I replace my 3D printer nozzle?
There's no fixed interval. Replace it when clogs keep coming back after cleaning, the tip looks worn or rounded, or print quality drops and calibration doesn't fix it. A brass nozzle can wear out within hours on abrasive filament.
Related articles
Sources & further reading
- Prusa Knowledge Base — Clogged nozzle (CORE One, XL, MK4/S, MK3.9/S)
- Prusa Knowledge Base — Cold pull (MK4 family, MK3.5, XL)
- UltiMaker Support — Clean the nozzle (hot and cold pull)
- Bambu Lab Wiki — How to avoid nozzle clogs
- Bambu Lab Wiki — Filament guide: nozzle recommendations
- E3D — V6 nozzle: hot tightening and cleaning
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