The extruder clicks or skips

Symptom

You hear a click, knock or snap from the extruder and sometimes the filament moves back a little. It usually comes with gaps or thin lines in the part.

Likely causes, from most to least likely

1. Clogged or partially clogged nozzle (or heat creep): the motor can't push and skips steps. A loud click points to the nozzle.
2. Asking for more plastic than the hotend can melt: speed or maximum volumetric flow set too high.
3. Nozzle too close to the bed on the first layer, blocking the plastic's exit.
4. Nozzle temperature too low for that filament.
5. Extruder idler tension set wrong, or dirty or misaligned gears. A light click points to the gears.
6. Retraction too fast or pressure advance too high.

Checks to tell which one it is

• Note when it happens: only on the first layer (nozzle too low), on fast infill (flow), all the time (clog) or when retracting (retraction).
• Heat the nozzle and push the filament by hand: if it is very hard to push or comes out thin, there is a clog.
• Pull the filament out and look for bite marks; check whether the gear teeth are packed with plastic.
• Compare temperature and speed with the slicer's material profile.

Before you start

Before taking anything apart, cleaning or adjusting it, switch the printer off and unplug it, unless a step says otherwise, and do not touch the nozzle, the heater block or the bed until they have cooled down. If in any doubt about electricity, heat or moving parts, stop and ask a professional.

Step-by-step fix

1. Check the first layer

   If it only happens on the first layer, raise the nozzle slightly with the fine Z adjustment until the lines are flat but not see-through.

   Check: The clicking stops on the first layer.

   If that does not fix it: Lower the speed or raise the temperature.

2. Lower the speed or raise the temperature

   Reduce the speed or the profile's maximum volumetric flow and check the temperature. If needed, Prusa suggests raising the nozzle temperature by 5-15 °C, staying within the filament manufacturer's range.

   Check: The extruder stops skipping on fast sections.

   If that does not fix it: Check whether the nozzle is clogged.

3. Unclog the nozzle

   If pushing by hand is hard or nothing comes out, follow the clog procedure: push fresh filament by hand, thin needle from below or cold pull.

   Check: Filament comes out normally when pushed.

   If that does not fix it: Clean and adjust the extruder.

4. Clean and adjust the extruder

   Switch off and unplug the printer. Remove plastic from the gear teeth with a toothpick, a brass brush or compressed air; check that the gears line up with the filament path and that the motor gear's grub screw sits on the flat of the shaft, and set the idler tension as the manufacturer says: neither too loose nor too tight.

   Check: The gears turn freely and grip the filament without chewing it.

   If that does not fix it: Check the PTFE tube.

5. Check the PTFE tube

   Make sure the PTFE tube isn't blocked or deformed and that the filament slides freely through it.

   Check: The filament slides through without catching.

   If that does not fix it: Adjust retraction and pressure advance.

6. Adjust retraction and pressure advance

   If the clicking matches the retractions, lower the retraction speed. On Klipper, a very high pressure advance (the documentation mentions values above 0.200) can make the extruder skip: lower the acceleration or the value.

   Check: The extruder no longer skips when retracting or changing speed.

   If that does not fix it: If it still skips with everything checked, contact technical support: it may be the motor or its electronics.

Prevention

• Use the material profiles for your nozzle and don't print faster than the hotend can melt.
• Clean the extruder gears from time to time.
• Calibrate the first layer so the nozzle isn't blocked.

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Printers it applies to

Any FDM (filament) 3D printer, from any brand.

Official sources

This guide summarises the official documentation linked here:

• Extruder noises · Prusa Research
• Clogged nozzle (CORE One, CORE One L, XL, MK4/S, MK3.9/S) · Prusa Research
• Max volumetric speed · Prusa Research
• Pressure advance · Klipper