If your filament is grinding, the printer is missing a few layers, or you’re getting clogs, it’s very likely you have filament stuck in the PTFE tube.
However, motor clicking, an overworked engine, under extrusion, and even a full print stop can all indicate the same issue.
The filament is stuck in the Bowden tube and it’s blocking new filament from coming out. Here, issues can happen for a variety of reasons, including heat, extrusion settings, bed settings, and even old filament.
Removing broken filament stuck in a tube is normally simple. Heat your hot end, let it sit at temperature for a few minutes, then use a wire to push the filament out. Long-term, fixing the issue might involve long-term maintenance or switching your filament supplier.
6 Causes Of Filament Getting Stuck In Tube
There are plenty of reasons broken filament can get stuck in the tube.
However, you’ll have to diagnose the issue based on the likelihood or based on how the issue happened.
1. Dirty Nozzle
Dirt or buildup around the edge of the nozzle can reduce the flow of filament, causing the buildup of cooling plastic and eventually a clog.
However, the same issue can happen if a small piece of debris, such as a tiny piece of plastic, a pin, etc., is caught in the nozzle.
Here, you’ll likely see light under-extrusion issues followed by motor stress and clicking and a full clog. However, clogs might also happen after you stop the printer, as liquid plastic is trapped in the nozzle by debris.
When you turn the 3D printer back on, you’ll have a clog.
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You can also check if the issue was a clog when you remove the broken filament from the tub, for example, if there’s debris in the plastic you remove.
2. Damaged PTFE Tube
If your Bowden tube is old or worn, it may have difficulty feeding filament, no matter your retraction settings. That can result in symptoms like under extrusion.
However, if your filament is also brittle, you might also start seeing more breaks. This is very likely to be an issue if you frequently have filament breaking inside the tube, rather than stopping at the nozzle first.
In most cases, Bowden or PTFE tubes have to be replaced about every year. However, they are cheap parts and you can normally pick up OEM options for under $15.
3. Contaminated Filament
If filament is left sitting out, it can collect dust and debris, which can cause it to clog.
In addition, filament should never be left out or kept outside of a package without a dehumidifier or silica. That’s because filament absorbs a significant amount of moisture, which can cause it to become more and more brittle over time.
Moisture exposure can cause even high-quality filament to become brittle over time, which may result in the filament breaking in the tube or at the nozzle. When that happens, you’ll have to replace the filament to prevent the issue from recurring.
4. Heating Issues
Heating issues can cause filament to clog or to become stuck. This often happens with inconsistent heating such as heating and then cooling, heating dropping off, suddenly hitting cold air, or even inconsistent heating zones in the nozzle.
Those issues can stem from a variety of issues, including poor temperature settings, printing when the outside air is too cold, a broken thermistor, broken or damaged thermistor wiring, or even a damaged hot end.
In most cases, heating issues result in partially melted filament hardening while still in the nozzle. This causes a jam or a clog, resulting in a backup of filament and potentially a breakage further up the tube.
Like other clogs, the break can be where the filament feeds into the tube or at the nozzle, which can make removal difficult.
However, diagnosing this issue can be difficult. This means you may have to rule out other causes before deciding on a temperature or heat issue.
Heating issues can also happen if you leave your printer sitting heated for a very long time. The hot end will keep the plastic melted. Then, when you start a new print, the plastic will push through to the cold side of the hot end, causing it to solidify and clog.
5. Leveling Issues
If the hot end is too close to the bed, it can cause clogs and nozzle breakage. This might be because of a leveling issue or because the layers are set too low. E.g., if you have a 0.4mm nozzle but a 0.2mm first layer.
Here, filament cannot feed through the tube. Often, the result is a break in the tube.
However, you can also check for this issue by opening the printer to look at the idler wheel. If the filament is ground down by the feed gear, it’s a very good sign that you either have a clog or leveling issues.
Leveling issues might be because the bed is uneven. However, it might also be the layer settings in your splicer. You’ll have to troubleshoot and check.
It’s always a good idea, though, to re-level as a first step, especially if you have an automatic leveler.
6. Old or Cheap Filament
Filament will always get more brittle as it ages. That’s more true if your filament is exposed to light or to moisture.
However, the longer you store it, the more likely it is to be brittle. That can result in a significant increase in filament breakage, even without other issues.
That’s also true if you’re buying cheap or low-quality filament. What you save in the cost of filament per roll could be lost in the cost of failed prints, under extrusion, and the hassle of removing blocked filament from PTFE tubes.
Unfortunately, there’s no fix except to replace the filament.
How To Remove Stuck Filament From PTFE Tube
In most cases, there’s only one real way to remove stuck filament from a PTFE tube.
Use a Wire
- Raise the extruder to the highest position.
- Heat the hot end, usually to 200-250°C, and let it sit at temperature for a few minutes.
- Open the casing (where necessary) to expose the gear-feeding filament into the tube.
- Use a stiff wire such as a thick paper clip, a 0.4mm or smaller drill bit or Allen wrench, or a low flexibility wire to push the wire up through the nozzle into the tube.
- If possible, use a pair of needle nose pliers to grab the filament from the feed gear and pull it out.
If you can’t push the filament up through the nozzle, you may want to push the filament from the other end. However, you may also want to try the next method.
If the filament is in the tube, you may be able to straighten the tube with the help of someone else or with a vise, and then use a long wire to simply push the filament out.
Heat the Hot End
It’s common advice to heat the hot end as high as possible to try to remove filament clogs. However, it’s important to keep the heat tolerance of your filament in mind.
If you burn the filament, it’s going to be harder to remove. Instead, check the heat tolerance of your filament, heat it to that point, and then let it sit at temperature for a few minutes before trying to remove the clog.
Then, use a pair of needle nose pliers to remove the clock from the front of the nozzle.
You can also take steps to prevent the filament from breaking in the PTFE tube in the future. For example:
- Source high-quality filament and use it within 12 months of purchase.
- Push a few millimeters of filament through the extruder after your last print to push any liquid filament out of the tube – then retract the filament so you don’t waste it.
- Check the nozzle and bed for dirt and debris before starting a print.
- Replace any broken or damaged thermistor wiring or parts.
- Routinely level the bed.
- Check layer height settings, especially after changing nozzles.
A small amount of preventive maintenance can prevent many of the issues that cause filament to get stuck in the PTFE tube.
Soak in Acetone
If the above methods don’t work, you may be able to clean the nozzle with acetone.
However, this probably won’t work on the Bowden tube, as that may soften and damage the acetone as well. In this case, you’ll want to purchase a new Bowden tube.
- Heat the nozzle to maximum heat settings.
- Remove the nozzle from the machine, being careful not to touch the heat block.
- Let the nozzle sit for a few minutes.
- Try to remove any plastic that you can with an Allen wrench or wire and needle nose pliers.
- Place the nozzle in a jar of acetone and let it sit overnight.
- Clean the nozzle with a wire to remove any soft plastic. Check that there’s no buildup or burnt plastic.
This method will mean that you can’t print for several days. However, it will dissolve any plastic stuck in the nozzle.
Removal Of Broken Filament In Ender 3 & Prusa Mini’s Tube
If you have an Ender 3 or Prusa Mini, you can use these guides to remove broken filament from the Bowden tubes.
- Turn on the printer and click the control knob.
- Go to Control Settings –> Temperature –> Nozzle.
- Set the temperature at your material’s melting point.
- Wait and stand by for the hot end to get up to temperature.
- Squeeze the extruder lever and rotate the extruder knob to attempt to remove the filament that way.
- Use a wire or a 1.5mm Allen wrench to insert into the nozzle from the bottom to push the filament out. Make sure the extruder level is squeezed to release the filament’s grip.
See the user’s manual here.
- Open the access door on the top of the feed housing to check if you can see any jams or stuck filament.
- Undo the Allen bolt on the feed housing and remove the spring. Take note of where the bolt is in the housing, as putting it back too tight can cause jams. Remove the nut and the door from the opposite side.
- Check for jams or stuck filament. Use tweezers or needle nose pliers to remove it if so.
If you have a jam in the Bowden tube, simply unbolt that from each end and use a wire to push the filament out.
See the user’s manual here.
Jams and clogs are common issues on many 3D printers. If the issue is in your Bowden or PTFE tube, you can often fix the issue by heating the hot end and using a wire to push the material back. If you have a release lever for the filament, make sure you press that while doing so. In addition, in some models, you’ll have to open the housing to access the feed mechanism, which means breaks may be trapped there.