Quick diagnosis
A rhythmic clicking or skipping sound means the extruder cannot turn filament through at the rate it is being commanded to move, and that one sound can trace back to several different problems. It is not the same thing as under-extrusion: under-extrusion is what shows up on the finished part, thin walls or gaps between lines, while clicking is what you hear while it happens, often before it leaves any mark on the print. This guide works from the sound back to the cause, then points you to the right existing fix instead of repeating it here.
1. Listen for a clean click versus a grinding sound
A clean, evenly spaced click usually means the stepper motor is losing steps: it keeps trying to turn on schedule, but something further down the path pushes back harder than it can overcome, so the drive gear skips teeth against the filament without doing much damage to it. A grinding or crunching sound is different, especially if a length of filament pulled back out shows a flattened side or a gouge cut into it, which means the gear teeth are chewing into the plastic rather than slipping cleanly over it.
Pin down which one you are hearing before touching anything. A clean click points toward resistance further along the path, a clog, a cold nozzle, or a bound feed line. Grinding points more directly at the extruder mechanism itself, and idler tension is the first thing worth checking.
2. Check the spool and feed path for tangles or binding
Before adjusting any setting, pull a length of filament off the spool by hand with the printer idle and feel for resistance. A spool that binds, catches on a crossed loop, or will not turn freely at the holder puts the same load on the extruder that a clog does, forcing it to fight for every millimeter, which produces the same clicking sound even though nothing inside the hotend is wrong. Tangles usually start when a loose end works its way under an earlier wrap while the spool keeps spinning during a retraction, and a holder with too little friction makes this worse by letting the spool coast after the extruder has stopped pulling.
If you find a snag, unspool it and rewind it under light, even tension rather than yanking it free. Then check the rest of the path for a pinch point, a kinked guide tube or filament rubbing against a cable or the printer’s frame.
3. Check idler tension and inspect the filament for gouges
Idler tension set too high presses the drive gear teeth deep enough into the filament to flatten it or cut a visible gouge along one side, and that damaged section struggles to feed cleanly even after it clears the gear, one of the more common causes of grinding rather than a clean click. Tension set too low has the opposite problem: the gear cannot grip hard enough to turn the filament at all, so it spins in place against the surface without leaving much of a mark, and the print starves rather than clicks.
Most extruders use a spring-loaded lever or an adjustable screw rather than a torque figure you can dial in precisely, so treat the manufacturer’s default as a starting point. Prusa’s own guidance for its idler screw sets it close to flush with the housing before any adjustment, one documented example of what “correct” looks like. From there, fine-tune by feel: firm contact, but not so tight that a pulled-back length comes out flattened or dented.
4. Check nozzle temperature against the material spec
If the nozzle is not hot enough for the material loaded, filament reaching the melt zone does not soften as fast as the extruder is trying to push it in. The plastic backs up and resists the motor in almost the same way a clog would, even though the nozzle itself is completely clear, a separate failure from a physical obstruction that needs a different fix.
Raise the temperature toward the higher end of the filament manufacturer’s documented range, rather than guessing at a number, and watch whether the clicking settles within a few layers. A genuine clog will not respond to added heat. It is also worth confirming the slicer profile actually matches the filament loaded, since a profile left over from a different material is an easy way to end up printing colder than the plastic needs.
5. When to move on to the clogged-nozzle or under-extrusion guide
If the spool feeds freely, idler tension looks reasonable, and temperature matches the material, but the clicking continues at a steady rate regardless of what you change, a restriction inside the nozzle is the most likely remaining cause. Work through the guide to clearing a clogged nozzle next, since it covers the safe way to find and remove a blockage without repeating those steps here.
If the clicking has stopped but the print still comes out with thin walls or gaps between lines, that is genuine under-extrusion: flow rate or e-steps are commanding more plastic than the hotend can melt and deliver in time. The under-extrusion guide covers calibrating those settings directly. The two problems overlap often but are not the same entry point. Clicking is a specific sound with several possible mechanical causes, while under-extrusion is a visible result that clicking is frequently, but not always, a sign of.
Extruder clicking checklist
- Sound identified as a clean, evenly spaced click or an active grinding or crunching noise.
- Spool turns freely by hand with no tangles, binding, or pinched feed tube.
- Idler tension checked against the manufacturer’s starting point, then adjusted by feel, not by guesswork.
- A length of filament pulled back through the extruder checked for flat spots or gouges.
- Nozzle temperature confirmed against the loaded material’s documented range, not a leftover slicer profile.
- If clicking persists, moved on to the clogged-nozzle or under-extrusion guide instead of repeating checks.