Key Takeaways

  • Clogged nozzle: Filament can get stuck and grind against the extruder gears. Clean the nozzle regularly and use filtered filament.
  • Incorrect temperature: Filament can melt too slowly or too fast, causing grinding. Adjust the extruder temperature according to the filament type.
  • Excessive retraction: Filament can break or bunch up in the extruder. Reduce the retraction distance and speed until the grinding stops.
  • Damaged extruder gear: Filament can slip or jam in the extruder. Replace the extruder gear if it is cracked, chipped, or dirty.

Filament grinding is when the teeth in the gears of your extruder strip material from your filament as it’s fed through- causing it to come out shredded and broken.

Filament grinding can be caused by a wide range of problems, from filament issues and incorrect slicer settings to mechanical problems with your 3D printer,

In this guide, I’ll help you work out why you’re experiencing filament grinding, drawing on over 5 years of 3D printing experience

I’ll also share exactly what steps you should take to solve the issue and prevent it from happening again so you can get back to stress-free 3D printing.

Diagnosis

Solve Your Filament Grinding

Your other symptoms will reveal the cause of your filament grinding:

extruder tension
Source: Reddit

Filament Grinding Causes and Solutions

Clogged Nozzle

blockage on the end of the bowden tube
There was a blockage at the end of the Bowden tube, also note the extruder gears biting into the filament. Source: Reddit

A blockage forces filament against the nozzle edge, misaligning it and causing it to grind against the extruder gears.

Symptoms

  • No extrusion (or poor, uneven extrusion)
  • Clumps of filament on the nozzle
  • Trouble feeding in fresh filament

How to Fix

  • Cool down your 3D printer.
  • Use a sharp tool like an acupuncture needle to clear the nozzle.
  • For superficial clogs, use a wire brush to clean the hot end.
  • Try cold pulling: manually draw cold filament through the extruder to clear remnants.

Additional tips:

  • Regularly clean your hot end and nozzle, especially after printing with abrasive materials like glow-in-the-dark filament.
  • Use filtered filament to reduce dust and debris that can contribute to clogs.
  • Be careful not to overtighten the nozzle, as this can damage the threads and make it more likely to clog.

For a deeper dive into clog issues and cleaning, see our detailed article on clogged nozzles.

Printing Too Cold

filament grinding at lower print temperature
Filament grinding was solved by printing at a higher temperature at the nozzle. Source: Reddit

If your extruder temperature is too low for your filament, the filament will not melt quickly enough, remaining too solid as it moves through the extruder. This will cause it to grind against the extruder gears.

Symptoms:

  • Poor bed adhesion
  • Improperly bonded layers

How to fix:

  1. Incrementally increase your extruder temperature by 5℃ until the filament melts smoothly and evenly.
  2. Record the optimal temperature for future use.

Additional tips:

  • Check the recommended settings laid out by your filament manufacturer.
  • If you’re already printing with the maximum suggested extruder settings, then the problem with your filament grinding in the extruder is likely from a different cause.

Printing Too Fast

Print speed
Source: Reddit

If the print speed is excessive and the feed rate isn’t adjusted to match, the filament may bunch in the extruder and grind against the gears.

Symptoms:

  • Bunched filament in the extruder
  • Blurry finish on printed parts

How to fix:

  1. Reduce print speed in 10mm/s increments until the filament grinding stops.
  2. Check your settings align with the manufacturer’s recommendations.

Additional tips:

  • Reducing print speed can also lead to filament grinding caused by issues such as heat creep and hot end jams.
  • To fix heat creep, try the following:
    • Lower the print temperature in small 5°C increments.
    • Increase the speed of your hot-end fan.
    • Install a new hot end, preferably a PTFE-lined hot end.

Wet or Damaged Filament

Model printed in wet filament
This model was printed using wet filament. Source: Reddit

Most 3D printer filament is hygroscopic, meaning it absorbs airborne moisture over time leading to imperceptibly thicker filament.

This extra thickness causes the filament to not fit smoothly through the extruder, resulting in grinding.

Symptoms:

  • Brittle filament
  • Warped prints

How to fix:

  • Prevent wet filament by storing it in opaque, airtight containers and avoiding direct sunlight.
  • Test for brittle filament by gently bending it back on itself. If it snaps, you’ll want to consider a replacement spool.
  • Use a filament dry box or DIY option like a food dehydrator to remove moisture from wet filament.
Filament storage
Filament storage boxes using cereal containers (Source: Reddit) and a storage that has hygrometers per box (Source: Reddit)

Additional tips:

  • Inspect the filament before each use for signs of damage.
  • If the filament is brand new and grinding, it is likely due to poor quality control. Buy filament from reputable retailers and manufacturers that impose strict standards for the quality of their filament.

Incorrect Nozzle Width

When your nozzle is too narrow for your filament, it causes the filament to get stuck and grind against the extruder gears.

Although most filaments work well with a standard 0.4mm nozzle, thicker filaments, such as 2.85mm, require a wider nozzle.

Symptoms:

  • Under-extrusion (filament is not coming out of the nozzle at the desired rate)
  • Over-extrusion (too much filament is coming out of the nozzle)
  • Clogged nozzle
  • Poor print quality (e.g., rough surfaces, uneven layers)

How to fix:

  • Check your filament diameter – either by reading the packaging, or measuring with calipers.
  • Use our nozzle sizing guide to find the ideal nozzle width for your filament diameter.
  • If you are unable to check the diameter of your filament, start with a larger nozzle and then work your way down to a smaller nozzle until you achieve the desired print quality.

Additional tips:

  • Once you have found the ideal nozzle width for your filament, you will need to adjust your slicer settings accordingly to reflect the mechanical change.

Retraction Issues

There are two main retraction settings that can cause filament grinding: retraction distance and retraction speed.

Retraction issues
Issue was resolved by reducing retraction settings. Source: Reddit

Retraction distance is the amount of filament that is pulled back into the nozzle. Retraction speed is the speed at which the filament is pulled back into the nozzle.

If the retraction distance is too long, it can cause the filament to get stuck in the nozzle. If the retraction speed is too fast, it can cause the filament to break.

Symptoms:

  • Frequent nozzle clogs
  • Stringing (thin strands of filament connecting different parts of the print)

How to fix:

  1. Clean your nozzle to eliminate clogging as a factor.
  2. Check your manufacturer’s instructions for the ideal retraction settings. If you can’t find theses, a good starting point for retraction settings is 5-10mm for distance and 25-40mm/s for speed.
  3. Test to see if the filament grinding stops.
  4. If the grinding does not stop, reduce your retraction settings by about 50% until it ceases. Incrementally increase your retraction settings until you find the ideal setting.

Additional Tips:

  • If you’re finding your manufacturer’s recommendations to yield filament grinding, check forums dedicated to your printer model to see what other users recommend.

Nozzle Too Close to Heat Bed

3D Printer Nozzle Too Close to Bed

When the nozzle is too close to the heat bed, it can cause the filament to stick to the extruder, and ultimately grind against the gears.

Symptoms:

  • Filament sticking to the extruder’s incise (the sharp edge of the extruder nozzle)
  • Poor print quality (e.g., rough surfaces, uneven layers)

How to fix:

  1. If you have automatic bed leveling, follow the procedure on your printer to level the bed.
  2. If not, you can level your bed correctly using the “paper method”.
    • Place a piece of paper between the nozzle and the heat bed
    • Manually lower the nozzle until you feel a slight resistance as you pull the paper.
  3. Once you have achieved the correct nozzle height, tighten the screws that secure the nozzle in place.
  4. Try a test print and make small z-offset adjustments until you get clean, consistent layers.

Additional Tips:

  • You must use the paper method at regular intervals across the bed to ensure the same nozzle height all across the build plate

Idler Tension Too High

Filament grinding--check tension in extruder
One of the things to check when there’s filament grinding is the tension in the extruder. Source: Reddit

The idler gear is a gear on the extruder that helps to grip and push the filament through the nozzle. If the idler tension is too high, it can cause the filament to grind against the extruder gear.

Symptoms:

  • Under-extrusion (filament is not coming out of the nozzle at the desired rate)
  • Clogged nozzle

How to fix:

  1. Locate the idler screw on your extruder.
  2. Loosen the idler screw slightly.
  3. Test the filament to see if it is still grinding.
  4. Repeat steps 2 and 3 until the filament is no longer grinding.

Additional tips:

  • If the idler screw is not adjustable, you may need to replace the idler gear with a smaller or softer one.
  • Make sure that the idler gear is properly aligned with the extruder gear.
  • Clean your nozzle regularly to prevent clogs.

Damaged Extruder Gear

cracked extruder arm
Cracked extruder arm led to the filament being misaligned. Source: Reddit

The extruder gear is a gear on the extruder that helps to grip and push the filament through the nozzle.

If the extruder gear is damaged it won’t turn as efficiently as it should, and grind against both the filament and other parts of your 3D printer.

Dusty or debris-covered gears can also cause filament grinding, as they don’t leave sufficient space between the gear and filament as it extrudes.

Symptoms:

  • Under-extrusion
  • Clogged nozzle
  • Poor print quality

How to fix:

  1. Inspect the extruder gear for signs of damage or blockage. Look for any cracks, chips, or other imperfections.
  2. If the extruder gear is damaged, it must be replaced.
    • When you replace an extruder gear, you must re-calibrate your printer’s e-steps to ensure that the printer is extruding the correct amount of filament.
  3. If the gear is simply dirty, you can clean it carefully with a hard brush.

Additional tips:

  • When replacing the extruder gear, make sure that you get the correct size and type of gear for your printer.
  • Be careful not to overtighten the extruder gear, as this can damage the gear or the extruder motor.
  • Clean the extruder gear regularly to prevent dust and debris from building up.

Damaged Bowden Tube

Over time, the PTFE Bowden tube that connects the extruder to the hot end can bend and degrade to the point of obstructing filament flow. This added friction causes filament grinding.

Burned bowden tube
Bowden tube burned. Source: Reddit

Symptoms:

  • Signs of damage like kinks, holes or deterioration.
  • Trying to manually feed filament through a damaged tube requires excessive force.

How to Fix:

  1. Replace any visibly damaged Bowden tubes with a new, high-quality tube.
  2. Make sure the tube is cut to the proper length for your printer and securely fastened at both ends with no gaps.
  3. Check that the hot end lining tube is also in good condition and correctly aligned with no gaps between the nozzle and heat break.

Additional tips:

  • Replacement tubes are fairly low cost. I recommend branded Capricorn tubes, one of the most highly regarded manufacturers of Bowden tubes.

Power Supply and Cooling Issues

Faulty power delivery to the extruder motor (or inadequate cooling of the extruder motor or mainboard) can cause filament grinding.

the cooling fan was off
This is what happens when your fan doesn’t work properly…

Symptoms:

  • The extruder motor lacks power or skips steps.
  • The extruder drive chip or mainboard overheats.

How to Fix:

  • Use a multimeter to check the power supply, mainboard, and extruder motor voltages. Ensure they match the expected values for your printer.
  • Replace any components outputting abnormal voltages.
  • Check motor cables for damage and replace them if needed.
  • Ensure the extruder motor cooling fan works properly. Replace if faulty.

Additional Tips:

  • Consider adding a fan to cool the mainboard if it doesn’t already have one. An overheating mainboard can limit power delivery, indirectly affecting your fan and extruder motor functionality.

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