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There's PLA filament clogged in my Bowden tube, is there a best practice for cleaning it out or do I need to replace the whole tube?

Also, the couplings are totally stuck, so I guess those would need replacement too or are there ways to get stuck couplings off?

Click here for a video.

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  • $\begingroup$ I use a pipe cutter and cut the last quarter inch off - what I want to know is why it happens in the first place $\endgroup$
    – Robert
    Commented Apr 19, 2020 at 15:39

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As a short-term fix, grab a twist drill bit that is on the order of 1.5 mm diameter (assuming a 1.75 mm tube). Using a hand drill, slowly and gently drill out the clogged filament. Obviously you want to try to avoid scarring the teflon lining, so better to use the thinnest drill that will work.

With a little training and a little luck, you'll get the clog cleared. I would recommend removing the nozzle first so that the chips don't fall into the nozzle.

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    $\begingroup$ Usually, the Bowden tube is 2 mm in inner diameter $\endgroup$
    – Trish
    Commented Jan 25, 2022 at 9:02
  • $\begingroup$ @Trish 1.9 mm is also pretty common these days. $\endgroup$
    – 0scar
    Commented Jan 25, 2022 at 22:35
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If you are able to force the filament from the interior of the bowden tube without causing damage to the tube, you will be able to determine the cause of the clog. My bowden tube clogged recently, but it was because I left the system idle with old filament inside. The filament broke from brittleness and the edge of the broken pieces managed to wedge against the tube.

I was able to use a "healthy" piece of filament along with great force (pliers pushing close to the tubing end) and remove the damaged filament.

Once removed, the new filament slid easily within.

Your PTC fittings may not have to be replaced if the tubing is not damaged inside and if the existing spacing meets your requirements. A PTC fitting has a ring of teeth which gouge and/or grasp the outside of the tubing preventing removal. It is frequently necessary to push the tubing into the fitting, then compressing the release ring followed by pulling the tubing.

The PTC fitting at the end where only the filament exits is probably a stock fitting. The fitting which has the bowden tube extending through it has been drilled and may be challenging to find. Your best source for such a fitting is the original manufacturer.

It's clear in the video that the threaded portion of the two fittings are different.

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  • $\begingroup$ The problem is I can't force the filament anywhere. It's totally stuck even with pliers. The ptc fittings are also totally stuck in place even when the lock mechanism is released. I just bought a replacement $\endgroup$
    – Matt
    Commented Sep 17, 2018 at 21:48
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    $\begingroup$ that's good that you have a replacement. With such damage, even if the filament was removed, it would probably give you problems in the future. $\endgroup$
    – fred_dot_u
    Commented Sep 17, 2018 at 22:02
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I haven't tried this, but it's possible to melt filament inside a PTFE bowden tube; some have even used this for splicing filaments. The examples I saw were over a flame but controlled heating would probably be better. If you do this, weld the clog to another piece of filament then push or pull once it's started to cool.

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Most standard filaments soften at 200 °C, meaning a pot of near-boiling water should soften whatever is stuck, allowing you to either fuse another strand of filament to it or use it to push it out of the tube.

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