Filament stuck in cold end  

  RSS
kevin.r19
(@kevin-r19)
Active Member

Hi guys,

I was happily printing my first own print on my one day old MK3 and then the white PLA I had loaded snapped while unloading. I could just see a little piece of it sticking out of the PTFE tube beneath the extruder gears:

I read https://shop.prusa3d.com/forum/prusa-i3-kit-building-calibrating-first-print-main-f6/filament-stuck-in-cold-end-t3561.html that I should either heat the hotend up without the cooling fan so that the expanded PLA can soften and be pushed through with the small allen key, or to disassemble it and put the whole hotend without electronics in an oven at 110 so that it can be pushed through.

Method no. 1 didn't make the filament move. I heated it to 290 and waited for about eight minutes until I got uncomfortable having no cooling on the heatsink, but even pushing forcefully on the stuck piece didn't move it.

I tried removing the nozzle at the recommended temp of 285 but all I managed to do was to severely scratch both the nozzle and the heatblock. It won't move at all, something I've never seen with my other E3D's.

Any help would be very appreciated, I'm a little saddened to have this huge of an issue so early on.

Posted : 07/04/2018 12:24 pm
peter.l22
(@peter-l22)
Honorable Member

I'm thinking that the worst-case scenario is that you take the extruder apart and replace the PTFE tube. The PTFE tube is $1.69, but it's out of stock right now.

Posted : 08/04/2018 3:18 am
joe.m14
(@joe-m14)
Estimable Member

This may be a very stupid idea...

Maybe if you heat the hot end, and remove the nozzle then you can get at the clog.

When someone asks you if you're a god, you say, "YES!"...
Posted : 08/04/2018 5:27 am
david.t28
(@david-t28)
Honorable Member

Have you tried pushing it back down? I had this happen to me because it forms a bulb on the end if you don't get it out fast enough. If you can push it down, cut the end off and then pull the filament out that's the best way if you can do it.

Posted : 08/04/2018 5:40 am
kevin.r19
(@kevin-r19)
Active Member

Thanks for the replies 🙂 Some more investigation over the weekend leads me to believe that this is actually PLA that got heated up enough while sitting close to the warm extruder gears to become soft. Or maybe it's a combination of this and the cooling while unloading.


I'm thinking that the worst-case scenario is that you take the extruder apart and replace the PTFE tube. The PTFE tube is $1.69, but it's out of stock right now.

I have PTFE here, it wouldn't be a problem. I disassembled the Extruder but the hotend is stuck completely. It appears that the PTFE tube expanded both below and above the plate beneath the gears. I can't pull or rotate it. Took a short video of it:
[youtube] [/youtube]

This may be a very stupid idea...

Maybe if you heat the hot end, and remove the nozzle then you can get at the clog.

This is actually one of these things that work for many people, so not a hugely stupid idea I think if you do it judiciously (ie don't cook it ;). It didn't help me in the end because there seems to be a huge amount of PLA in there that expanded both below and above the plate.

Have you tried pushing it back down? I had this happen to me because it forms a bulb on the end if you don't get it out fast enough. If you can push it down, cut the end off and then pull the filament out that's the best way if you can do it.

That was the first thing I tried, but it was already completely blocked unfortunately.

So now I have to decide between breaking the extruder cage and trying to salvage the hotend or breaking the hotend 😕

Posted : 09/04/2018 11:00 am
kevin.r19
(@kevin-r19)
Active Member

I removed the blob by blowing on the tube still sitting in the extruder case with a hair dryer as suggested by andrew in this thread: https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/filament-jam-t15506.html . Now if only I could remove the hotend so I can fix the PTFE tube :mrgreen:

Posted : 09/04/2018 11:20 am
chris.p8
(@chris-p8)
Trusted Member

Looking at your video - can you get a razor blade or something similar and slice the 'lump' off the end of the PTFE tube, and then pull it out in the other direction as the 'lump' will not be stopping it?

Think whatever you try now will involve a certain amount of disassembly?

Best of luck

Chris

...
Posted : 09/04/2018 11:46 am
kevin.r19
(@kevin-r19)
Active Member

Thanks for the suggestion! I have not been able to pull it out of the extruder body far enough to get a blade inside. Maybe I'll try to cut it off from the top though. I reassembled it and if I cautiously load the filament manually the printer prints well. I'll steer clear of PLA for now 😉

Posted : 09/04/2018 3:14 pm
mitch.m3
(@mitch-m3)
Active Member

I have EXACTLY the same fault as Kevin.
I was doing a 24 hour PLA print and it jammed. The bond-tech gears have such grip and drive that the filament had buckled and compressed inside the PTFE tube.
As Kevin demonstrated in his video; it seems that the only way to extract the E3D heatsink is to sacrifice the body of the extruder assy.
You cannot remove the heatsink when the PTFE tube is full of expanded PLA.
The rear part of the extruder assy needs to be modified so that the heatsink can be removed with the PTFE tube.
I also wonder why Prusa used a low-speed fan when the throat of the cooling duct is so small. I think that the throat needs to be made bigger so that the fan can actually push air past the heatsink! I.E. get some airflow rather than having the fan permanently stalled.

Kevin: how did you fix your hot end blockage?

...
Posted : 06/05/2018 12:05 am
sean.h8
(@sean-h8)
Honorable Member

Ok guys, pulling the heatsink out is a bear of a task in itself, you can NOT "angle" the heatsink out, you have to pull it out "flat". I don't know how to explain it... basically pull towards you, THEN down. Do *NOT* angle the heatsink, as that will cause it to bind, and make it impossible to remove. This is ONE of my biggest annoyances of the Prusa extruder design.

Hi, I'm Sean. I used to work on CNC machines.
I try to not make mistakes, but the decision is YOURS.
Please feel free to donate to my filament/maintance fund....
Posted : 07/05/2018 12:06 am
vsobr
(@vsobr)
Active Member

I got similar problem today - the filament got stuck and there seemed to be filament dust on the wheel of the extruder. to extract the filament I had to tear it and then use a wire to push the remnat down trough the tube set for 260°C.

are the two wheels badly placed when this happens?

Posted : 25/04/2020 12:44 am
joan.t
(@joantabb)
Veteran Member Moderator

@vsobr

A picture might help

Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 25/04/2020 1:58 pm
lars-2
(@lars-2)
Active Member

Seems to be the time for this problem:) I have the same problem, as my filament ran out mid-print and I wasn't prepared to put in a new one. I tried heating to 235 and pressing with a 5mm allen wrench, then with a smaller metal pin, no go for either. Here's a shot before I did those:

I suspect my attempts at pushing it has caused it to expand enough to not go through the tube. I considered doing what chris-p8 suggested, but I'm more likely to cut gashes in the PTFE tube that will cause further problems.

I'll try with removing the nozzle next, though I could see the danger that heating to 285 as per nozzle changing instructions would cause problems when there's filament in there. Any thoughts on that?

Thanks,
-Lars

Posted : 25/04/2020 3:02 pm
lars-2
(@lars-2)
Active Member

Update: I was unable to push it in any way, even after removing the nozzle. Eventually I took the extruder assembly apart enough to get the heat sink off (surprisingly easy to do) and heated it in the oven until I could pull the filament out.

Afterwards, the hotend doesn't heat to more than 140C. I'm not sure what caused this, the electronics all test fine. Though now that I write this I wonder if trying to push the filament through with no nozzle in has allowed filament to creep into the innards of the heat block and is messing things up there. 

-Lars

Posted : 04/05/2020 6:57 am
Share:

Please Login or Register