Cleaning a hotend means removing burnt or stuck filament from the outside of the nozzle, the heater block and the silicone sock, and clearing the nozzle bore when flow gets weak. For the outside, Prusa’s procedure is short: heat the nozzle to 250 °C for 3 to 5 minutes so leftover plastic softens, scrape it off with a small brass brush while keeping the brush away from the hotend cables, then let everything cool to room temperature (about 10 minutes) before you touch it.
This guide covers what to clean and in which order, how to do it without burns or short circuits, and when cleaning the outside is not enough. Blockages inside the nozzle have their own guides: see unclogging a nozzle and the cold pull method. The steps and temperatures come from Prusa and Bambu Lab documentation linked at the end. The 250 °C figure is Prusa’s; on other printers treat it as a starting point and stay below your hotend’s rated maximum.
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Hotend cleaning in 6 steps
- Put on heat-resistant gloves and clear the area around the toolhead.
- Heat the nozzle from the printer’s own menu to 250 °C (Prusa’s value) and hold it for 3 to 5 minutes so residue softens.
- Brush the nozzle and heater block with a small brass brush. Prusa says any hard-bristled brush will do if you have no brass one. Pick off soft blobs with tweezers or wipe the nozzle firmly with a paper towel, as Bambu Lab’s guide does.
- Switch the heater off and wait until the display shows ambient temperature. Prusa gives about 10 minutes and says to check the display values before touching anything.
- Inspect: the nozzle tip is clean, the wires are intact, the silicone sock is not torn, and the nozzle and heater block have no play when you push them.
- Load filament, extrude a few centimetres to confirm smooth flow, then start a short test print.
Safety before you start
- Burns. Prusa’s articles open with the warning that heated parts can cause severe burns. Read the temperature on the display rather than judging by eye, and wear heat-insulating gloves if you must work on a hot hotend (Bambu Lab).
- Heat only from the printer menu. Prusa states plainly never to use an external heat source on the hotend. A heat gun or lighter can damage the heater block, wiring and plastic parts.
- Cables. Prusa warns that touching the hotend cables with the brush can cause a short circuit. Brushing is done with the printer on and the nozzle hot, so keep tools clear of the wiring. Anything that means unplugging a connector, pulling a fan or touching the toolhead cable is done cold, with the printer switched off and disconnected from power (Bambu Lab’s instruction).
- Maintenance modes. Bambu Lab’s maintenance mode keeps the hotend heated while you work, but it stops heating after a while for safety, so reheat if you are not finished.
- Don’t force anything. If plastic resists, it is either not hot enough yet or there is a mechanical problem that needs a proper disassembly.
What to clean, and how
| Part | What builds up | What to do |
|---|---|---|
| Nozzle exterior and heater block | Burnt filament, small blobs | Heat to 250 °C for 3 to 5 minutes (Prusa), brush with brass, keep away from cables, cool fully |
| Silicone sock | Melted filament stuck to it | Remove with heat-resistant gloves and clean until no filament is left (Bambu Lab); replace it if it is torn |
| Nozzle bore | Partial clog, old colour | Push fresh filament hot, then cold pull; a thin needle only on standard nozzles (see below) |
| Heatsink fins and hotend fan | Dust and filament fluff | Remove the fan, blow dust off with canned air, clear threads with tweezers; never blow air into a running fan (Prusa) |
| Extruder gear | Filament dust | Look for dust on the teeth; Prusa’s clog article also turns the motor shaft by hand to feel for catching or grinding |
Cleaning the silicone sock and a stuck nozzle
Bambu Lab’s blob guide removes the silicone sock with heat-resistant gloves and cleans it until no filament is left on it. If the sock is torn or will not hold its shape, replace it rather than refit it.
On Bambu Lab quick-release hotends, a thin film of filament can keep the nozzle from coming out when it is cold. Bambu’s guide cuts the filament with the cutter lever, heats the nozzle to 220 °C, pries the locking tab open with tweezers and removes the nozzle. It then wipes the nozzle surface firmly with a paper towel and wipes the base of the heating assembly. Wait for the parts to cool before you refit the nozzle and sock. Other printers have their own procedure, so follow your maker’s guide for the model you own.
Clearing the inside of the nozzle
If the outside is clean but extrusion is still weak, work through these in order. They follow Prusa’s clogged-nozzle article; the temperatures are Prusa’s, so adjust them for your hotend and material.
- Push fresh filament hot. Prusa heats to 260 °C for PLA or 280 °C for PETG, ASA and other higher-temperature materials, waits about 2 minutes, then pushes filament in by hand.
- Cold pull. If flow does not return, follow the cold pull guide. Prusa notes it is unlikely to work after a failed push, so it is mainly for residue and partial clogs.
- Pull out visible filament. If a little filament shows above the nozzle tube, Prusa heats to 280 °C, grips it with needle-nose pliers and pulls slowly.
- Needle or wire. Prusa pushes a 0.3 to 0.35 mm wire or the supplied acupuncture needle about 1 to 2 cm into the nozzle from below, with filament loaded and gloves on. It says this method is not suitable for high-flow nozzles, whose internal shape differs.
- Replace the nozzle. If flow still does not come back, the blockage is higher up or the nozzle is damaged. Changing the nozzle is usually quicker than another hour of cleaning, and worn nozzle signs tell you if wear is the real problem.
Blobs, heat creep and when to take the hotend apart
A print that detaches and wraps molten filament around the nozzle is a different job from brushing. Bambu Lab’s guide for this uses maintenance mode, heats the hotend slightly above the previous material’s print temperature (around 250 °C for PLA in its example), and removes the part cooling fan and the sock to reach the blob. It warns against taking the toolhead off the X-axis rail, because the steel balls in the slider can fall out. Follow the guide for your own model rather than improvising.
Extrusion that stops mid-print while the printer keeps moving, often with a clicking extruder, can be heat creep rather than a dirty nozzle. Prusa lists insufficient airflow over the heatsink, dust on the fins, an ambient temperature above roughly 35 °C or an enclosure, and a nozzle temperature set too high among the causes. Its checks start with the fan: make sure it pushes air towards the heatsink, and clean the fins. The same article gives 4000 to 4400 rpm as the expected nozzle fan speed on the printer it describes, which you can read from the menu there.
Common mistakes
- Brushing or scraping a cold nozzle. Residue is soft only when the hotend is hot, and forcing it risks bending the wiring.
- Using a heat gun, lighter or torch instead of the heater.
- Running the brush across the thermistor and heater wires.
- Pushing a needle into a high-flow nozzle, or forcing it when it meets resistance.
- Skipping the fan and heatsink. Dust there causes heat creep, which looks like a clog.
- Cleaning again and again when the nozzle is simply worn or the hotend is running above its temperature limit; see all-metal vs PTFE-lined hotends for the limits.
Frequently asked questions
How often should I clean my hotend?
There is no universal interval. Prusa’s maintenance list has quick checks before each print, a check of axes, belts and fans every 200 hours of printing time, and fan cleaning after every few hundred hours. Clean sooner when you see burnt specks, blobs on the nozzle or weak extrusion.
Should I unplug the printer before cleaning the hotend?
Not for the hot brushing step, because the nozzle has to be heated from the printer’s menu. Keep tools away from the wiring and let the hotend cool fully afterwards. For anything that involves unplugging connectors, removing fans or touching the toolhead cable, switch the printer off and disconnect it from power first.
Can I clean a nozzle with a needle?
On standard nozzles, yes: Prusa pushes a 0.3 to 0.35 mm wire or acupuncture needle 1 to 2 cm in from below with filament loaded. Do it gently and with gloves. Prusa says the method does not apply to high-flow nozzles, so check what nozzle you have first.
Can I burn residue off with a heat gun or lighter?
No. Prusa’s guidance is to heat the hotend only from the printer menu and never to use an external heat source, which can damage the heater block, wires and nearby plastic. Use the heater, a brass brush and patience instead.
