Problems unloading filament.. Jamming in PTFE tube  

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jweaver
(@jweaver)
Honorable Member

Is anyone else having problems with unloading filament from cold?

If I leave PLA installed. When I come to unload it, the printer heats.. RAMS.. Purges and unloads.. And more often than not, the filament jams in the PTFE  tube between the extruder and hotend.

Removing this tube is a trival task.. And when I look, the end of the filament has a slight 'blob' on it, meaning it won't enter the PTFE tube..

Its easy to extrude a little filament. Cut the end off and unload... But this whole process unnecessarily complex.

 

Surely this isn't normal? Is anyone else seeing this? Has anyone found a solution?

 

I am wondering if heating.. And then purging a few times and then unloading might help.

 

I wonder if their unload logic should include a longer purge, just to soften the end of the filament??

 

Thoughts?

 

Posted : 20/02/2020 2:27 pm
bookaroo
(@bookaroo)
New Member

Same here, happen about 50% of the time.

 

Posted : 20/02/2020 9:11 pm
jweaver
(@jweaver)
Honorable Member

I think the solution might be to purge before unloading.. i am going to start doing this to see if it helps.

Posted : 20/02/2020 9:48 pm
bookaroo
(@bookaroo)
New Member

Maybe it’s better in 4.0.3 of the firmware just released, I did not anything about that in the release note. I think it does purge a little bit before itself... what I have seen is the end of the filament is bigger than the tube and had time to solidify... and the tube is pretty tight too, I had to replace them in the E3D v6 of the MK3S.

Posted : 20/02/2020 11:40 pm
jweaver
(@jweaver)
Honorable Member

I have 4.0.3 but its the same.

Posted : 20/02/2020 11:53 pm
kirajib904
(@kirajib904)
New Member

If the filament is stuck in the white Teflon tube, you need to take the hotend out from the extruder. Use the guide to do so (steps 2 - 5). You will be left with the hotend exposed, hanging in front of you. Preheat it via LCD Menu -> Settings -> Temperatures -> Nozzle and see if you can remove the filament by pulling it up from the PTFE tube using pliers.

Posted : 22/02/2020 5:17 am
bookaroo
(@bookaroo)
New Member

@kirajib904

What I do is unscrew the PTFE fitting either on top of the extruder or the hot end push the filament cut it than it ejects normally.

Posted : 22/02/2020 6:00 am
jweaver
(@jweaver)
Honorable Member
Posted by: @kirajib904

If the filament is stuck in the white Teflon tube, you need to take the hotend out from the extruder. Use the guide to do so (steps 2 - 5). You will be left with the hotend exposed, hanging in front of you. Preheat it via LCD Menu -> Settings -> Temperatures -> Nozzle and see if you can remove the filament by pulling it up from the PTFE tube using pliers.

Its not stuck in the hotend. It gets stuck in the long tube between the hotend and extruder.. dead easy to fix.. but annoying.

Posted : 22/02/2020 9:05 am
simonbugler
(@simonbugler)
Active Member

I've had this problem - I solve it by doing a Purge immediately before an unload. This seems to stop it getting stuck.

Posted : 22/02/2020 11:01 am
kirajib904
(@kirajib904)
New Member
Posted by: @jweaver
Posted by: @kirajib904

If the filament is stuck in the white Teflon tube, you need to take the hotend roadrunner email out from the extruder. Use the guide to do so (steps 2 - 5). You will be left with the hotend exposed, hanging in front of you. Preheat it via LCD Menu -> Settings -> Temperatures -> Nozzle and see if you can remove the filament by pulling it up from the PTFE tube using pliers.

Its not stuck in the hotend. It gets stuck in the long tube between the hotend and extruder.. dead easy to fix.. but annoying.

Thank you very much.

Posted : 24/02/2020 3:11 pm
Julian
(@julianr)
Trusted Member

Also check the tightening of the extruder idler and try loosening it a bit.

Using the exact same filament, my own Mini was handling it fine while my dad's would frequently jam. Turned out his idler was much tighter than mine. We loosened it a bit, I haven't heard any more complaints from him so far.

Posted : 25/02/2020 9:44 am
crawlerin
(@crawlerin)
Honorable Member

@julianr

How would you subjectively describe is good level of pressure for idler? Do you still feel the spring when twisting, or not? How deep aporoximately is head of screw, or how much screw sticks on the other side? I had filament folded inside and around around extruder gear and had to open and clean those compartments. I didn't take mental note on how it was before and now I don't seem to be able to get it right 😣

Posted : 25/02/2020 12:47 pm
Julian
(@julianr)
Trusted Member

I don't think one can accurately describe that. You get a feeling for how hard to turn the screw must be when the tension is about right.

Perhaps photos are the next best thing. The screw head is nearly perfectly flush with the hole in the plastic (maybe inset by 0.2mm). The idler door is about 1mm inset against the plastic housing near the bottom where the screw sticks out.

This is how mine came preassembled, and on this machine I haven't had any filament jams yet.

Posted : 25/02/2020 2:41 pm
crawlerin
(@crawlerin)
Honorable Member

@julianr

Thanks. That's without filament I see, from photos. Mine may be still too tight then 🤔 That may be part of my rocky PETG journey.

Posted : 25/02/2020 5:14 pm
Olef
 olef
(@olef)
Honorable Member

I have seen posted elsewhere the screw head should be flush with the plastic with filament unloaded

Posted : 27/02/2020 6:45 am
simonbugler
(@simonbugler)
Active Member

mine is not flush when correctly fitted. 

when’s mine is flush it is actually disconnected...

if you screw all the way out the wheel swings out from the opposite side  you will see where the screw fits in

I screwed it in so it connected then with filament loaded just into the extruder you can move it back and forth whole tightening the screw. You just want it to grip it a little

 

 

 

 

Posted : 27/02/2020 10:49 am
jakub.kohoutek
(@jakub-kohoutek)
Active Member

I had the same issue - even after firmware upgrade to 4.0.3 the filament was getting stuck every time I tried to unload it.

The issue is the mentioned blob that forms in the hotend and can't pass the PTFE tube between the extruder and hotend, but IMHO it's only in combination with the bottlenecks in that PTFE tube.

After some investigation, I realized the blob is not that wide - it can't pass only through two specific places in the PTFE tube, namely through narrower areas where the two copper rings are (under the nuts on the picture):

I solved the issue by taking out the PTFE extruder-hotend tube and gently drilling the two narrow ends (using the 2mm drill) that effectively made the places wider. That fixed the issue for me - print quality hasn't changed and unloading the filament works as a charm now.

I hope it helps someone. There are no guarantees, just posting here what worked for me. Also if you plan to do the same fix, be very careful when drilling, you don't want to destroy the PTFE tube.

This post was modified 3 months ago by jakub.kohoutek
Posted : 01/03/2020 12:20 pm
stevensmith
(@stevensmith)
Estimable Member

@jakub-kohoutek

Did you drill the tube or the brass part?  

Posted : 01/03/2020 3:20 pm
steve-4
(@steve-4)
Estimable Member

Its simple guys ..... Do not unload from cold

The filament in the 'hot end' is cold and solid and no doubt stuck to the inside of the nozzel, warm your machine first or unload at the end of your job while its still hot.

😉 😉 😉 😉 

S

Posted : 01/03/2020 3:38 pm
jakub.kohoutek
(@jakub-kohoutek)
Active Member
Posted by: @stevensmith

@jakub-kohoutek

Did you drill the tube or the brass part?  

The tube, because it was too narrow in the area where the brass fittings are. They are probably too tight.

@steve-4 - I am using the "unload filament" option from the printer's menu that preheats the hotend before it tries to unload it, so it's not a cold unload. But still it didn't work. Many people are facing the blob at the end of filament issue and even though it should have been solved by the 3.0.4 firmware (see the github issue https://github.com/prusa3d/Prusa-Firmware-Buddy/issues/199 ), it's not.

Posted : 01/03/2020 4:25 pm
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