Extruder clicking or skipping: what the sound means

This guide is for anyone whose extruder has started clicking, knocking or grinding, with thin lines, gaps or no plastic coming out. It explains what the sound means, which causes Prusa, Bambu Lab, Creality, Polymaker, Simplify3D and OrcaSlicer document, and the order to check them in. Procedures that only apply to particular printers are labeled with the models they cover.

What does the clicking mean?

Prusa explains the sound in its clog article for the CORE One, CORE One L, XL, MK4/S and MK3.9/S. When the hotend or nozzle is partly or fully clogged, "the internal resistance against the flow of the filament is greater than what the gears are able to push. As a result, the gears are skipping, leading to the 'clicking' noise and, in most scenarios, also to the grinding of the filament."

Polymaker describes the same thing from the motor's side: the extruder stepper "does not have enough torque to overcome the amount of force needed to push filament through your nozzle." When that happens, you'll see the drive gear skip and get under-extrusion, uneven extrusion or no extrusion at all.

If the gear keeps slipping in one spot, it can chew through the filament. Simplify3D says the drive gear can grind away "enough plastic from the filament so that there is nothing left for the gear teeth to grab on to," which many people call stripped filament. Signs include "lots of small plastic shavings" and a motor that spins while the filament doesn't move.

Loud click or light click (Prusa Nextruder printers)

Prusa's clog article for the CORE One, CORE One L, XL, MK4/S and MK3.9/S gives a quick way to narrow it down:

• Loud clicking: "most likely suggests the nozzle is clogged or deformed."
• Light clicking: "can most likely point to the gearing."

This is Prusa's guidance for its Nextruder printers. Other extruders may sound different, so treat it as a hint, not a diagnosis, on other machines.

What makes the extruder skip?

Step 1: Check the spool and feed path

Start with the cheapest check. Creality's K1 series feeding guide lists filament tangled on the spool or at the PTFE tube inlet as the first cause of gears turning with no filament coming out, then blockages at the extruder's front shell, in the hotend's PTFE tube, and in the hotend throat. Polymaker adds that "resistance at the spool or pathway leading to the extruder will also cause problems," along with sharp bends in the path.

Make sure the spool turns freely, the filament isn't crossed under another wrap, and any tube from the spool isn't kinked. If you're out of filament, Simplify3D's first check for a printer that stops extruding is simply that there is still filament leading into the nozzle.

Step 2: Is the first layer too close?

If the clicking happens on the first layer and stops once the print is a few layers up, look at nozzle height before anything else.

• Polymaker: when the nozzle is too close, "there is no room for it to escape," so the motor can't push any more material. The filament gets stripped or the motor skips.
• Simplify3D: the giveaway is a print that "does not extrude plastic for the first layer or two, but begins to extrude normally around the 3rd or 4th layers." Its fix is a Z-axis G-code offset in small steps, for example 0.05 mm, to move the nozzle further away.
• Prusa (first layer issues, MK2/S to MK3.5/S): a nozzle too close essentially blocks its opening. Adjust it with Live Adjust Z and First Layer Calibration.
• Bambu Lab (A1 series): a first layer that's too low can leave the nozzle "nearly touching or scraping the plate surface," with "little to no filament being extruded." Bambu says to run bed leveling before printing, especially after changing or replacing the build plate.

Our first layer adhesion guide covers nozzle height in more detail. If nothing comes out for the first moves of every print, our guide to no extrusion at the start of a print also covers an empty nozzle and the purge line.

Step 3: Slow down, and check temperature

An extruder can only melt so much plastic per second. Push past that and the gear slips.

• Slow down. Polymaker calls printing too fast "a common reason" for skipping, and suggests turning the feed rate down mid-print, to 90% and lower, to see whether the clicking fades. Simplify3D suggests cutting the printing speed by 50% as a test. For basic non-geared extruders on inexpensive printers, Polymaker's rule of thumb is no faster than 100 times the nozzle diameter, so about 40 mm/s with a 0.4 mm nozzle. It says newer fast machines such as Bambu Lab's can run much faster.
• Respect the flow limit. OrcaSlicer explains that max volumetric speed "varies depending on your material, machine, nozzle diameter, and even your extruder setup," and even by brand and color. Its calibration test finds the limit, and it suggests setting the result 10 to 20% lower for print quality. It warns that "printing at high volumetric speed can lead to poor layer adhesion or even clogs."
• Check temperature, within range. Simplify3D suggests raising the nozzle 5 to 10 degrees so the plastic flows more easily. Polymaker agrees, but only if there's no heat creep or clog, and normally within the filament's recommended range. Prusa's Nextruder under-extrusion article suggests trying plus or minus 5 to 15 °C for filament brands that aren't in PrusaSlicer.
• Smaller nozzles are more prone. Polymaker says the smaller the nozzle, the more likely the motor will skip.

Step 4: Rule out heat creep before raising temperature

Heat creep softens filament too high in the hotend, where it swells and jams. Prusa's heat creep article for the MK2.5 and MK3 family says the extruder motor "grinds into the filament" and "can even make a 'clicking' or 'ticking' sound." The usual pattern is a print that starts normally, then stops extruding while the printer keeps moving.

• Prusa (MK2.5 and MK3 family) lists a room above 35 °C (30 °C for some filaments), PLA in a closed enclosure, too high a hotend temperature, poor heatsink airflow and slow filament flow among the common causes.
• Bambu Lab says the most common reason for clogs on the X1 Carbon and P1S is heat building up inside the enclosure. With PLA on the Textured PEI or High-Temperature PEI plate, it recommends printing with the front door open and/or the top cover removed.
• Polymaker warns that if heat creep is the cause, "increasing your extrusion temperature will only make the problem worse."

Our heat creep guide covers the full checks.

Step 5: Idler tension, gears and retraction

• Idler tension. Prusa's heat creep article (MK2.5 and MK3 family) says that with the idler too loose "the gears can't grip the filament and the motor can start skipping," and too tight, the gear teeth "might grind the filament and get choked." Polymaker adds that an over-tight idler can flatten the filament until it's too wide to feed, but that going too loose causes under-extrusion. On the Nextruder (CORE One, CORE One L, XL, MK4/S, MK3.9/S), Prusa says the two idler tension screws are set at the factory, and if they've been disturbed, the screw tips should line up with the front surface of the Idler Nut.
• Dirty gears. On the Nextruder, Prusa says filament debris can build up in the feeding gear's grooves, and suggests compressed air, a brass brush or a toothpick through the access hole. Creality's K1 series guide says to check the extruder gear for debris, clean it with a soft brush, and replace the extrusion kit if the gear is damaged or deformed.
• Gearbox (Nextruder). Prusa says a gearbox that isn't fully aligned, especially after opening the cover, can cause under-extrusion. The CORE One, MK4/S and MK3.9/S have a gearbox alignment procedure; the XL has manual steps in the same article, though Prusa's clog article says the XL gets the alignment procedure in the printer menu from firmware 6.4.1, so check your firmware version.
• Retraction. Simplify3D says a retraction that is too fast or too long can put "excessive stress on your extruder," and suggests halving retraction speed as a test. For the Ender-3 V3 SE, Creality traces clicking while printing to retraction speed and says to lower it from 40 mm/s to 25 mm/s.

Step 6: Treat it as a clog

If the feed path is clear, the first layer isn't too low, and slowing down doesn't help, the nozzle is the likely cause. Simplify3D reaches the same conclusion: if grinding continues after raising temperature and slowing down, "it's likely your nozzle is partially clogged." Our clog diagnosis guide links each maker's unclogging procedure by model.

Two related points from the sources:

• Changing materials. Prusa (Nextruder printers) says to load a lower-temperature filament at the previous, hotter filament's temperature, so the new filament pushes the old one out. Polymaker warns that leftover ABS in a hotend running PLA can cause skipping, and suggests a cold pull that starts at the previous filament's temperature until none of the old material shows.
• Wet or low-quality filament. Polymaker suggests drying the filament or trying a new spool if slowing down doesn't help. Prusa says low-quality filaments with inconsistent diameter or impurities can jam the Nextruder gears or nozzle.

If skipping goes on after all of this, our under-extrusion guide covers flow calibration and the other causes of thin lines.

Extruders without gearing

Polymaker says that with a non-geared extruder, especially a Bowden setup "such as a stock original Ender 3," you are likely to run into skipping eventually. It says a geared, dual-drive, direct extruder shouldn't have skipping as an issue unless the first layer is too close or the nozzle is clogged, and that the gear ratio is what makes the difference. It adds that even stock settings and parts can still lead to skips on the basic extruders that come on inexpensive machines. Its suggestions for older printers with stock non-geared extruders are slower speeds, moving up from a nozzle smaller than 0.4 mm, and an extruder with a proper gear ratio as an upgrade, which then needs new E-steps.

When should you contact the maker?

Contact your printer's support if the gear is damaged, the extruder motor doesn't turn at all, or clicking continues after the checks above. Creality's K1 series guide says that if the extruder gears don't rotate during automatic feeding, the problem might be the extruder motor or a connection board, and to check the motor's wiring. Prusa says that if you feel harsh resistance, catching or grinding when turning the Nextruder motor shaft by hand with the gearbox removed, there may be debris deep in the gearbox, a worn gear or a fault in the motor.

Print problems: what to check before you buy ↗