How to Clean a 3D Printer Nozzle and Fix a Clog

A clogged nozzle is partly or fully blocked, so filament cannot flow out properly. Prusa's guide describes the cause as damage to the nozzle or impurities in the filament that make it stick in the hotend. This guide covers how to spot a clog, how to clear it, and how to stop it coming back.

Safety first. The nozzle can cause severe burns. Prusa warns not to touch the hotend while it is hot, to use protective gloves, and to heat the nozzle only through the printer's menu, never with an external heat source, which it says can cause damage. Always follow your printer maker's instructions.

How to tell if the nozzle is clogged

Prusa lists the signs:

• Filament does not come out of the nozzle when loading, even though it reaches the extruder gear.
• A partial clog shows as gaps and missing layers, or as filament that curls up and sticks to the nozzle.
• Clicking from the extruder. Prusa says loud clicking most likely points to a clogged or deformed nozzle, while light clicking may point to the gearing. Skipping gears can also grind the filament.

See fix extruder clicking and fix under-extrusion for the related symptoms.

Step 0: Rule out the extruder

Before you blame the nozzle, check the feed. Prusa says debris can build up in the grooves of the feeding gear and cause insufficient extrusion. It suggests lifting the idler and cleaning the gear with compressed air, a brass brush or a toothpick. Check that the filament is not ground or kinked above the extruder.

Step 1: Try a hot push with new filament

Prusa's procedure for its printers (applies to high-flow and standard nozzles) is:

1. Open the extruder idler and remove any fittings on top so you can reach the filament path.
2. Heat the nozzle through the printer menu. Prusa gives 260 °C if you were printing PLA, or 280 °C for PETG or ASA.
3. Wait 2 minutes, then push new filament in by hand and see if it flows or drips.
4. If it flows, load filament and run a short test print to confirm.

Prusa adds that if flow does not return, the nozzle most likely needs replacing, with the blockage further up. Check your own filament's allowed range before heating beyond it. These temperatures are for Prusa hotends.

Step 2: Clean a standard nozzle with a needle

For non-high-flow nozzles only, Prusa describes heating to the temperature for the material, introducing the filament, then inserting an acupuncture needle (supplied with the printer) or a thin wire of 0.3 to 0.35 mm into the nozzle from below to a depth of about 1 to 2 cm. Prusa warns that material may start to flow suddenly, so use protective gloves. Then load filament and check it flows, repeating several times. Prusa says these steps do not apply to high-flow nozzles because of their internal geometry.

Step 3: Cold pull

A cold pull pulls a plug of cooled filament out of the nozzle, taking residue with it. Prusa notes that its printers have a dedicated cold pull procedure (and an automatic one on some models), and that it recommends trying it if available even when the push method failed. Follow the exact steps for your printer, because temperatures and technique vary. This is also covered by the maker's guide if you have a printer from another brand.

Step 4: Pull the filament out with pliers

If a bit of filament is visible at the top of the nozzle tube, Prusa says you can heat the nozzle to 280 °C and firmly grab the filament with needle-nose pliers, then slowly pull it upward until it is fully removed. It recommends following this with a cold pull.

When to replace the nozzle

If none of the methods works, replace the nozzle. Prusa says that if flow is not restored after the push method, the nozzle most likely needs replacing. See hotends and nozzle materials and nozzle sizes explained.

How to prevent clogs

See how to store filament and how to dry filament, and keep up with the routine in the maintenance checklist. For temperature ranges that stay safe for your material, see PETG print temperature.