How to Clear a Clogged Nozzle: Cold Pull and Other Methods

The extruder pushes the filament but nothing comes out of the nozzle, or only a thread-thin line does. The nozzle may be clogged. Most clogs come from dust, burnt plastic, low temperature or heat that has crept to the cold side of the hotend (heat creep). The good news is that most clogs can be cleared with a "cold pull", without removing the nozzle.

Clog or something else?

The symptoms can be confused with under-extrusion. To tell a clog apart, look at these:

• When you push filament by hand, no plastic comes out of the nozzle, or only a very thin amount does.
• The extruder gear clicks and pushes the filament back. See Extruder clicking.
• The plastic coming out of the nozzle is not straight but curls sideways. This is a sign of a partial clog.
• In the middle of a print, the layers suddenly thin out and stop.

If the plastic flows straight and easily when you push by hand, the nozzle is not clogged. In that case look at the other causes in the under-extrusion guide.

Causes of clogs

• Dust and dirt: Dust on the spool enters the nozzle with the filament. Common with spools that have been left out for a long time.
• Carbonized plastic: If the nozzle is kept hot for a long time, the plastic inside burns and forms a hard residue.
• Low temperature: If the filament does not melt enough, flow gets difficult.
• Heat creep: Heat climbs to the cold side of the hotend and the filament softens before it should. It happens if the hotend cooling fan fails or with very long retractions.
• Switching materials: When switching to PLA after a material printed at a high temperature such as ABS, the ABS left in the nozzle does not melt and clogs it.
• Nozzle too close to the bed: If the nozzle is pressed into the bed on the first layer, the plastic cannot come out. In that case the problem is not a clog but the Z offset.

Safety note

The nozzle and hotend heat above 200 °C. Wear gloves when working on a heated hotend and keep your face back. When removing or tightening the nozzle, hold the heater block with a separate wrench. Otherwise you can bend the heater block's connection or tear the wires.

Fix 1: Heat and push by hand

Sometimes the clog comes only from low temperature.

1. Heat the nozzle to the upper temperature limit of the filament you are using (220–230 °C for PLA).
2. Take the filament out of the extruder and cut the end square.
3. Push the filament by hand, slowly and with steady force.
4. If the plastic starts coming out straight, push a few more centimeters and the clog is cleared.

Fix 2: Cold pull

The most effective and safest method. It pulls the dirt out of the nozzle by sticking it to the filament.

1. Heat the nozzle to the printing temperature of the material and push a little filament so the inside melts.
2. Lower the temperature. About 90 °C for PLA; for nylon or a special cleaning filament, the value the manufacturer recommends.
3. When it reaches the target temperature, pull the filament up with a firm, decisive motion.
4. Look at the end of the filament. You should see a cone-shaped tip taking the inner shape of the nozzle, with black residue on it.
5. Repeat 2–4 times until the tip comes out clean.

On printers with a Bowden tube the pull is done through the tube. You need to open the extruder gear's arm and release the filament.

Fix 3: Cleaning needle

Many printers come with a cleaning needle slightly thinner than 0.4 mm.

1. Heat the nozzle to printing temperature.
2. Gently push the needle up through the nozzle tip, a few millimeters in.
3. Then push filament from above so the dirt flows out.

The needle loosens dirt at the tip but leaves it inside, so using it together with a cold pull gives better results. Do not force the needle; a broken needle tip is a new clog.

Fix 4: Replace the nozzle

Nozzles are consumables and cheap. If the methods above do not work:

1. Heat the nozzle to printing temperature. Removing it cold strains the threads.
2. Hold the heater block with a wrench and turn the nozzle counterclockwise to remove it.
3. Fit the new nozzle by hand, then tighten lightly while hot to the torque the manufacturer recommends.
4. Check the first layer and Z offset again with the new nozzle.

Brass nozzles wear quickly with carbon fiber, glass fiber or glow-in-the-dark filaments. Use a hardened steel nozzle for these materials.

To prevent a repeat

• Store spools in a closed box away from dust. If you like, add a small sponge filter to the filament path.
• Do not leave the printer hot after a print. Most printers do this automatically.
• When changing materials, do a few centimeters of purge extrusion with the new filament at the old material's temperature.
• Make sure the hotend cooling fan works. This fan runs continuously while the printer is on and the hotend is hot.
• Do not overdo retraction distance. Going above 6–7 mm on a Bowden or 2 mm on direct drive raises the heat creep risk. There is a separate article on this: Retraction settings.
• Wet filament also disrupts flow. If needed, dry the filament.

Frequently asked questions

Which filament is best for a cold pull?

Nylon and special cleaning filaments give good results because they stick firmly inside the nozzle and come out without breaking. If you don't have them, PLA works too.

How often should a nozzle be replaced?

With standard PLA and PETG a brass nozzle can be used for months or even years. If you use abrasive filament, replace it when print quality worsens or the nozzle hole grows.

How do I tell whether the nozzle is clogged or the extruder is the problem?

Take the filament out of the extruder and push it by hand. If it does not come out even by hand, the nozzle is clogged. If it comes out easily, the problem is in the extruder gear, the tension or the settings.