Filament Grinding: All Causes & Fixes Explained

Scott Hamill

Guides, 3D Printers, 3D Printing Guides

Filament Grinding

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Filament grinding is when the teeth in the gears of your extruder are pressed too hard against the filament, shaving off the material as it’s fed through. If your filament is in good condition but exits the extruder shredded, especially on one particular side, then your problem is likely filament grinding.

Filament grinding can be caused by filament issues, problems with your 3D printer, or inefficient slicer settings.

If you’re having an issue with your filament coming out of your extruder looking shredded and broken, check all the potential causes and solutions for filament grinding we’ll discuss today.

It’s worth noting that it could also be a combination of any of these issues, so be sure to check out each one to help you identify the issue, or issues, and fix them without too much fuss.

extruder tension
Source: Reddit

Filament Grinding Causes and Solutions

Grinding in 3D printing occurs when filament is pressed too firmly against the extruder gears. Various reasons contribute to this issue, and we offer efficient solutions for each.

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

Clogged nozzles can cause issues like poor extrusion, overheating, and potential 3D printer damage. A blockage forces filament against the nozzle edge, misaligning it and causing it to grind against the extruder gears. This not only harms your prints but exacerbates the clog. Signs of a clog include slow, uneven extrusion and peeling filament.

How to Fix

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

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

It’s worth being on the lookout for signs of a blockage. Common symptoms include poor or uneven extrusion, or if the filament is extruding, signs of curling. 

  • No extrusion – if the extruder is churning away but no filament is coming through the nozzle, this is a sign of a clog. The extruder skipping steps or clicking is another symptom of this.
  • Poor or uneven extrusion – filament is being extruded but is curling or producing uneven layers, especially first layers.
  • Clumps of filament on the nozzle – if you can visually see small clumps of filament on the inside edge of the nozzle then you’re likely seeing the start of a clog.
  • Trouble feeding in fresh filament – when feeding a fresh spool into the extruder/hotend, you may notice that it doesn’t reach the hot end. 

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 may not melt quickly enough, remaining too solid as it moves through the extruder. This can cause it to grind against the extruder gears, especially if you’ve recently switched to a higher temperature filament without adjusting your settings.

How to Fix

Incrementally increase your extruder temperature by 5℃ until you find the optimal setting, recording it for future use.

This approach helps you find the right balance and addresses other issues related to a cold extruder, like poor bed adhesion and improperly bonded layers.

When in doubt, always 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

Printing too quickly can cause several 3D printer issues, including filament grinding.

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.

How to Fix

To address filament grinding, reduce print speed in 10mm/s increments and observe the results. Verify your settings align with the manufacturer’s recommendations. If you’re near the upper limit, decrease the speed incrementally to find the optimal setting for your printer.

Reducing print also comes with diminishing returns because printing too slowly can lead to filament grinding caused by issues such as heat creep and hot end jams.

Heat creep is an issue where excess heat ‘creeps’ up the hot end causing filament to melt earlier than required. This impacts on the quality of the print with a common sign being an almost blurry finish to printed parts. Though there are many factors that can cause heat creep, such as excessive temperatures, poor cooling, and poor quality components, slow print speeds cause the filament to stay in the hot end for too long, melting it before it hits the normal heat zone.

The easiest fix is to bump up the print speed, but if you’ve hit a point where you need slower speeds to address filament grinding, the problem is likely linked to temperature, cooling, or poor quality parts.

Start by lowering the print temperature in small 5°C increments to reduce how much heat circulates inside the hot end. This should allow you to balance slower print speeds while warding off heat creep.

You can also bump up the speed of your hot end fan to ensure filament doesn’t melt too early. If your print doesn’t have a hot end fan, we strongly consider installing one. You’ll want to max out the fan speed, then lower it in small increments until you remove any instances of warping or other cooling issues and heat creep disappears.

Lastly, if the above doesn’t work, you’ll want to consider installing a new hot end. PTFE-lined hot ends are particularly well suited to combating heat creep because they insulate the filament before it hits the melt zone. If you have the cash, we recommend opting for a high quality hot end from a reputable brand like ED3 or Micro Swiss as even their all metal, non-PTFE-lined hot ends are designed to reduce instances of heat creep.

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 warped prints and imperceptibly thicker filament.

Excess moisture or wear can cause the filament to not fit smoothly through the extruder, resulting in grinding.

How to Fix

If your filament is aged or overexposed, it may be irreparable; prevention is key. Proper filament storage extends filament life and reliability. Use opaque, airtight containers and avoid direct sunlight. For moisture issues, consider filament dry boxes or DIY options like food dehydrators.

If the filament is brand new, then the issue is likely related to the quality of the material and the manufacturing process. Poor quality control can lead to inconsistent filament diameter throughout the spool, which can cause grinding. The extruder has to work harder to compensate for the variation.

You can use calipers to measure the filament diameter to ensure consistency throughout the spool. We recommend buying filament from reputable retailers and manufacturers that impose strict standards for the quality of their filament.

Brittle filament can also cause grinding. The main culprit here is moisture, but poor quality filament made from a low quality formula can also be brittle even brand new. Filament that’s been exposed to moisture for long periods can turn brittle, making it prone to breaking, which can lead to grinding. We recommend testing for brittleness by gently bending the filament back on itself. If it snaps, you’ll want to consider a replacement spool.

Filament Not Stored Properly

Filament storage
Filament storage boxes using cereal containers (Source: Reddit) and a storage that has hygrometers per box (Source: Reddit)

Filament storage isn’t just about protecting it from the elements. Properly storing filament on its spool is essential to prevent tangles, which can lead to extruder grinding, shredding, and clogs.

How to Fix

Tangling is often inevitable, as anyone who uses wired earphones knows. But by keeping filament on its spool and feeding it smoothly into the extruder, you can avoid these issues.

If your filament is already tangled, you can untangle it with our simple guide.

Incorrect Nozzle Width

Filaments vary in thickness, and using the correct extruder width is crucial for efficient printing. If the nozzle width is too narrow for the filament, it will cause a bottleneck 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. If you don’t adjust the nozzle for thicker filaments, they won’t extrude efficiently and will grind against the gears.

How to Fix

Verify the ideal nozzle width for your filament and adjust your hardware accordingly. While most nozzles and filaments come in standard sizes, it’s important to confirm measurements if unsure.

Nozzle size dictates the ability for the printer to heat up filament sufficiently during the extrusion process. While the physical nozzle plays its part, temperature and slicer settings do the bulk of the work. You’ll want to dial in your slicer settings to match your nozzle size otherwise the extruder will work overtime, leading to grinding. Slicer software is the best option here, but you can also explore more granular alternatives like Pronterface, which allow you to dive deeper into settings and truly fine tune settings to your hardware.

Retraction Issues

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

Retraction in 3D printing refers to the withdrawal of filament into the nozzle between layers to prevent unwanted drips and blobs. Slicer software usually allows retraction control. If you encounter frequent nozzle clogs and filament grinding, your retraction settings may be too aggressive.

How to Fix

Test this by reducing retraction settings by about 50% to see if grinding stops. Clean your nozzle before testing to eliminate clogging as a factor. If grinding stops after the test and nozzle cleaning, incrementally increase retraction settings to find the ideal setting, lowering both speed and frequency. The correct setting should help with layering and prevent filament grinding. 

We recommend setting retraction distance to 5-10 mm and the retraction speed to 25-40 mm/s as starting point, adjusting as needed based on results. Not all printers are alike so what may work for one may not for another. We recommend eyeing up forums dedicated to your model to see what other users recommend.

If the retraction settings are too intense, especially retraction speed and distance, then this can cause the extruder gear to lose its grip on the filament, resulting in all manner of problems, including grinding.

Retraction pulls filament out of the hot end melting zone when the nozzle isn’t actively depositing material to avoid unsightly stringing and build on the print itself. Simultaneously, the printer also cuts down on heating the space above, offering more control over the extrusion process.

Nozzle Too Close to Heat Bed

3D Printer Nozzle Too Close to Bed

When your nozzle is too close to the heat bed, filament may stick to the extruder’s incise, causing it to grind against the gears.

How to Fix

To fix this, adjust your nozzle height higher. Use a piece of paper to manually ensure a comfortable gap between the hot end and the build plate without excessive space. If problems persist, raise the nozzle height to 0.2mm instead of the usual 0.1mm to ensure proper filament extrusion into the model.

To fix the issue, level your bed correctly. If you have automatic bed leveling courtesy of a level probe like the BLTouch, follow the procedure on your printer to level the bed. After this adjust the z-offset using the paper method above. Position the paper between the nozzle and the bed, then slide it back and forth, lowering the height as you go, until you feel a slight resistance. Fire up a test print and make small z-offset adjustments until you get clean, consistent layers.

If your printer doesn’t have an automatic bed level feature, use the paper method above, ensuring the distance between the nozzle and the bed is identical across the surface of the bed. We recommend doing this at regular intervals across the bed to adjust for any inconsistencies in the flatness of the build plate. Refer to the documentation that came with your printer for a more detailed step-by-step guide to manually leveling the bed.

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

Filament grinding can result from factors other than the filament itself. A common oversight is idler tension, or extruder tension, which affects extruder gear performance. If set too high, the tension can grind and damage filament during extrusion. 

How to Fix

Extruders have a screw or two that you can adjust to change how tight the extruder’s gear grip is on the filament.

If it’s too tight, slightly loosen your extruder’s feeder (gear part) grip on the filament.

If not adjustable, replace the gear with a smaller or softer one, but confirm compatibility with your manufacturer to avoid under-extrusion issues.

Damaged Extruder Gear

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

Moving machine parts, including gears, wear over time. If your gear is worn then it won’t turn as efficiently as it should, and grind against both the filament and other parts of your 3D printer, leading to further damage.

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.

How to Fix

If dust or debris is the problem, carefully clean the gear with a hard brush.. Be very careful when doing this, as you don’t want to risk damaging the gear while cleaning it.

If the gear is worn or damaged, seek a suitable replacement. Consult your manufacturer for the best replacement options.

Damaged Bowden PTFE Tube

Burned bowden tube
Bowden tube burned. Source: Reddit

Classified as a consumable, the Bowden tube connecting the extruder to the hot end is likely  to wear out over time. If your PTFE Bowden tube is bent, twisted, uneven, has holes, or is otherwise damaged to the extent that it prevents the filament from feeding through smoothly, this can lead to grinding. 

The same goes for the PTFE hot end lining tube. Over time the tube can wear out, melt, bend, or fray, obstructing the filament path, which can lead to grinding. Ensuring a smooth filament path through the Bowden tube and into the hot end lining will keep resistance minimal and lead to optimal printing results.

Additional, incorrect Bowden tube set up can sometimes lead to under extrusion and grinding if it restricts movement. It’s crucial to have the proper Bowden tube length per your printer manufacturer’s recommendations and to ensure the couplers at either end hold it firmly in place.

How to Fix

Visually inspect your Bowden tube and hot end lining for any signs of damage, especially bends, twists, and degradation. Additionally, feed filament into the Bowden tube manually, checking that it doesn’t require excessive force for the filament to pass through. If you bump into any issues, replace the tube. Replacement tubes are fairly low cost. We recommend branded Capricorn tubes, one of the most highly regarded manufacturers for Bowden tubes.

Check that there are no gaps where the tube meets the print head assembly. The same goes for gaps between the nozzle and hot end lining. Gaps in both cases can cause filament grinding. Similarly, check that the nozzle and tubing are aligned correctly and properly held in place by the couplers both on the extruder and on the print head assembly.

Power Supply and Cooling Issues

A faulty power supply can lead to several issues that can cause grinding, chiefly those that affect the extruder motor and drive chip cooling. Without proper cooling, namely a working cooling fan, you’ll encounter heat build up and the extruder motor won’t function as intended, resulting in instances of grinding.

How to Fix

Check the power supply voltage and ensure proper current delivery to the stepper motors, including the one powering the extruder. Use a multimeter and test the output voltage of the CPU, ensuring it matches the values in your printer’s documentation, official website, and, often, on the label stuck to the printer itself. If the values are low, then you’ll need to either get the power supply repaired or replace it.

Use a multimeter and test the output voltage of the CPU, ensuring it matches the values in your printer’s documentation, official website, and, often, on the label stuck to the printer itself. You’ll also want to check the stepper motor in the same way. If you suspect there’s an issue from that initial test, use the multimeter probes to first test the 1st and 3rd pins for continuity, then the 4th and 6th pins. If the voltage is abnormal, get the motor repaired or replace it.

Check that the motor wiring is in good condition – look out for frayed cables, severe bends, and twists. Replace if you see any significant signs of damage.

Check and monitor that the extruder driver chip is providing enough current to the stepper motors. With improper cooling, the extruder drive chip can overheat, limiting the amount of voltage it can feed to the extruder stepper motor, which can cause grinding. Consider replacing the fan.

If all the above fails to fix the issue, it may be that the board isn’t being cooled sufficiently, in which case, check that the mainboard fan is working correctly. Check and monitor that the extruder driver chip is providing enough current to the stepper motors. With improper cooling or a faulty fan, the extruder drive chip can overheat, limiting the amount of voltage it can feed to the extruder stepper motor, which can cause grinding. Consider a replacement, or if it doesn’t have a fan, consider installing one.

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