Filament always stucks after print is done



  • what happens: after extruder cools down, part of filament becomes 2.3mm in size (a kind of swells up).
    and it takes much of effort to pull it out from there by hand.

    other scenario - is to try new print with same filament, but in such a case it does not print (filament does not go out).

    please advise.

    pic 1

    pic 2

    pic 3



  • So when I want to remove filament, I do so at full printing temperature. I have a macro which moves the effector down to help me get to it, increase hotend temp to 240 deg C. Then I remove the breech from the Nimble, grab the filament and pull it out smartly. You have to pull faster enough to get that wider bit out whilst its still hot.

    It will have a blob on the end like that, because the bore of the nozzle is just larger than 2mm. But pulling it out hot helps to clean the nozzle. I then clip the end off the filament I have just unloaded, so when I want to load it again it goes through any guide tubes which are 2mm diameter(not 2.3mm).

    I have long thought that it would make much more sense for any guiding tubes to taper in gradually until the nozzle which would be drilled to 1.8mm. But I am sure there is a good reason why this does not occur.


  • administrators

    Two suggestions;

    1. Make sure you are not retracting too much filament at the end of the print.

    2. To remove PLA filament from a E3Dv6 hot end, I heat the hot end to 100 to 120C, then pull the filament out. If instead you heat the hot end to a high temperature as DjDemonD suggests, you must retract the first 10mm of filament very slowly to avoid getting a blackage.



  • Edit. If I've understood the OP correctly, his problem is not about removing filament but rather trying to print again after a successful print.

    That's a classic case of heat creep. The extruder has 2 parts. A hot end and a cold end. What is happening is that heat is creeping up into the cold end, causing the filament to soften and swell in the area of the heat break or just above it. It isn't a Duet issue but here are some suggestions.

    The first one is that you need to let the hot end cool right down before turning off the fan. If you are doing that then here are some more suggestions.

    You need to have a sharp transition between the hot zone and the cold zone. This isn't happening. You haven't said what hot end it is so I can only make some general comments.

    If it's a cheap clone, buy a genuine one. Heat creep is one of the main issues with clones.
    If it's a genuine E3D, try using Lite heat sinks which have PTFE liners all the way through.
    I had exactly this issue with the stock diamond 5 colour hot end. The fix was to use a bigger fan to blow more air over the heat sinks. This fix my translate to other hot ends.
    HTH



  • Perhaps the op could chime in and say what he is actually asking/saying. I read it as he was surprised that the filament is wider at the nozzle than it is elsewhere and that its difficult to pull out cold, which it obviously will be.

    My removal technique is for abs, I'd expect pla to be much too stringy to remove quickly at 240 deg C. I'd still remove it sharply but at 150 deg C, if you try removing it too slowly that 2.3mm plug will cool, harden and won't come out.

    It's worth reading kraegars thread on 2in1 splitters and filament shaping to retract back out of the hotend automatically without jams and tails. He used a retract, pause, reinsert almost as far as he retracted, then pull back as fast as the extruder could go. Claimed several thousands of swaps with no feed issues.



  • @DjDemonD:

    Perhaps the op could chime in and say what he is actually asking/saying. I read it as he was surprised that the filament is wider at the nozzle than it is elsewhere and that its difficult to pull out cold, which it obviously will be.

    Agreed. I read it differently to you Simon. For info, my removal macro for PLA is heat to 180, then cool to 120, retract 20mm at 5mm\sec, then retract 50 mm at 10mm\sec, then yank the rest out at 50mm\sec. It took a fair bit of experimentation to get it right but it works well on my Diamond hot ends.



  • @DjDemonD:

    It's worth reading kraegars thread on 2in1 splitters and filament shaping to retract back out of the hotend automatically without jams and tails. He used a retract, pause, reinsert almost as far as he retracted, then pull back as fast as the extruder could go. Claimed several thousands of swaps with no feed issues.

    Sounds interesting - do you have a link ?



  • Don't worry, a quick search turned it up:

    https://www.duet3d.com/forum/thread.php?id=1010#p28993



  • thank you all for commenting and helpful links.

    my extruder is original E3D that came with smart effector. issue is indeed with heatbreak throat. i am able to print low temperature PLA but when it comes to 260 deg material is stuck even while the print 😞

    so, i put in bigger fan (40*40) at a price of not having fan for model cooling …. and ordered Chinese titanium throat with PFTE tube inside https://www.aliexpress.com/item/1Pcs-V6-Heat-Break-Hotend-Throat-For-Official-Teflon-Optimized-Fine-finishing-Titanium-alloy-1-75/32811983640.html?spm=a2g0s.13010208.99999999.297.59TPMu

    also there is an option to get nozzle that feeds in PFTE tube. did anyone tried it?
    https://www.aliexpress.com/store/product/1Pcs-3D-printer-3D-V6-V5-J-Head-brass-nozzle-extruder-nozzles-0-2-0-25/1032650_32809932122.html?spm=2114.12010612.0.0.230f49fcuO7l3r

    upd: or i guess high temperatures and no retract at all…



  • ok, i have got throat with PFTE tube inside and issus have gone. it can print up to 255 degrees.



  • @c310:

    ok, i have got throat with PFTE tube inside and issus have gone. it can print up to 255 degrees.

    Glad it fixed it for you. Don't be tempted to push the temperature any higher though - PTFE starts to give off nasty gases at around 260 degC


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