Filament stuck in filament tube, how to retrieve?  

RE:

When you look at the printer head you can see  white PTFE tube going into the print head via silver fitting with black cap/ring on it - this is a compressing tube fitting.

Push the plastic cap down with pliers and it will allow to remove the white PTFE tube, and you should see the filament inside. 

Carefully lift the tube and remove the filament. Look at the little marks on the PTFE tube - it gives you idea how far you need to insert it back - and then push the tube back ito the fitting. 

RE:

Oh one more thing, the ptfe tube and the fitting are under the black plastic cap https://help.prusa3d.com/guide/6-nextruder-assembly_849034#865778

And underneath is the compression fitting  https://help.prusa3d.com/guide/6-nextruder-assembly_849034#850542

You can see the black ring on the fitting, push it downward so it stop locking on the tube.

RE: Filament stuck in filament tube, how to retrieve?

While I am familiar with compression fittings in general, this particular one won't release the PTFE tubing, no matter what I do.  I have several of these in my parts box, so I was able to make sure which direction the collar has to move to release the PTFE tube.  However, I was able to unscrew the compression fitting from the top of the toolhead and run a piece of filament up into the PTFE tubing to - I hoped - push the filament out the other end.  This does not work - the stuck filament doesn't budge at all - apparently it binds when pushed, as opposed to pulled.

This is new - if something is causing the filament to stick in the tube then it's likely that the same thing is gripping the filament when printing and may be interfering with printing and contributing to the breaking stress - undo the tube at both ends and blow through it hard, try swinging the tube around to use centrifugal force ... 

But if this isn't working buy a new, not-sticky-inside tube and cut the old one open to find out what's causing the trouble so you can avoid repeats.

And let us know what it is.

Cheerio,

RE: Filament stuck in filament tube, how to retrieve?

That's kinda what I was afraid of - having to disassemble half the printer just to get a section of stuck filament.  I'll report back on results.

RE: Filament stuck in filament tube, how to retrieve?

I removed the right side wall to get access to the filament sensor assembly and was able to remove the short piece of PTFE tubing (and the even shorter piece of filament broken off inside it), but I could not remove the PTFE tube from the other end of the sensor assembly.  After reviewing the assembly information, I wound up having to destroy the black collet (blue arrow in picture below) that secures the PTFE tubing in the filament sensor assembly in order to remove the tubing. At the other end I was unable to get the PTFE tubing to release from the compression fixture, and I wound up cutting the tubing off the end.  After the PTFE tubing was free of the printer I was able to use another length of filament to push the broken filament out the other end of the tubing. Depending on how you counted them, there were at least nine different breaks in the filament.  This was PLA filament that had been in a dryer for a long time - apparently too long!  🤣 

I have plenty of spare PTFE tubing, and compression fitting for the extruder end (one that actually works).  However, I don't have a collet for the filament sensor end, so if anyone has an extra or has sourcing info for this part I would be grateful.  I have to say Prusa did not cover themselves in glory with their filament guide tube and filament sensor arrangement.  I've gone through at least two earlier Prusa printers, two different Flashforge IDX models and built a Voron 2.4/300 with a two toolhead MissChanger mod, and none of the others had such a Rube-Goldberg arrangement.  

Some parts of that tube look white - as if there was significant internal wear or a deposit on the inside - slice open the tube and examine the inside.  Check the surface of the filament too.

Cheerio,

RE: Filament stuck in filament tube, how to retrieve?

No, the PTFE tubing is pretty clean (I inspected it with a backlight) - the whiteness you see is due to the ineptness of the photographer 🙂

RE: Filament stuck in filament tube, how to retrieve?

Anyone know if this product from Amazon will work to replace the collet I destroyed?

Amazon.com: 20PCS Bowden Tube Coupler Collet Clamp Clip Bowden Collet and Clip Set Plastic Joint Fittings OD 4mm 3D Printer Accessories 1.75mm Filament Printer Parts : Industrial & Scientific

Your printer model is too new for much experience to have built up on the forum.  Contact Prusa Support via chat; you will need your printer's serial number.  They will be able to advise you wrt part numbers and compatibility.

Cheerio,

RE: Filament stuck in filament tube, how to retrieve?

Prusa really needs an improvement to this design. Frustrating to remove the PTFE tube from the side sensor! If anyone comes up with an alternative design, I'd be the first to print it.

RE: Filament stuck in filament tube, how to retrieve?

Well, my bad advice is:

Check your filament to see if it is brittle before putting it in the machine. Toss any brittle filament in the trashcan !!!

Do you have a filament drier?  Brittle filament can be caused by moisture absorption. So having a good drier can prevent your filament from going brittle on you.  Once dry, store in air tight containers with some molecular sieve to keep it dry.

Posted by: @frank-8

I had a bad (very brittle) batch of PLA filament, and it broke at both ends, ...-- any ideas or advice?

 

RE: Filament stuck in filament tube, how to retrieve?

As I mentioned at the start of this thread, that roll had been in my 92deg, 23pct drier for several months before installing it in the printer

RE: Filament stuck in filament tube, how to retrieve?

I looked back in this thread and did not see any mention of of filament drying. But, it is easy to check if a filament is brittle.  If it has been effectively dried and is still brittle then it is time to toss that filament.  

My drier recommends 55 C ( 131 F) at a minimum of 3 hours for PLA.  

I check for brittleness BEFORE I use my filaments.  Because having a brittle filament leads to a lot of breaks and tricky repairs to remove filament !

Once, when I was in a bind on my old Ender3, I slit my PTFE tube vertically for about 2" where the stuck filament was. I was then able to pull it out. I then wrapped the tube in tape to keep the slit closed. It worked in a pinch, but is not a recommended practice.

RE: Filament stuck in filament tube, how to retrieve?

As a footnote, some PLA filaments simply go bad with time and begin snapping like this. It doesn't appear to be moisture related, some plasticizer used in the mix is 'going away' and the filament becomes brittle.  I've had several brands do this over the years and I do a reasonable job keeping my filament dry (<5% RH  storage conditions).