Notifications
Clear all

Filament frequently gets stuck on ejection  

  RSS
WizardStan
(@wizardstan)
Active Member
Filament frequently gets stuck on ejection

After a print has finished (or failed and I hit stop) and it goes to eject the filament, there's about an 80% chance that the filament will get stuck.

Note that it is not getting jammed.  The hotend remains clear.  What it does is partially ejects the filament and then, as it's retracting, it gets a little bend at the end that causes it to get stuck.  It can't come out, it can't go back in.  Normally what I do is just pull on it until the little bend snaps and falls out, but this time I'd had enough and decided to disassemble the extruder to take some pictures and hope that someone has some insight.

I've disassembled this thing so many times, cleaned and refit everything.  This has been going on for months now.  It wasn't always this way.  I'm getting so unbelievably frustrated.  Why does it keep doing this?!

Bent filament against extruder gear

Bent filament near bowden tube

Closeup of removed filament

This topic was modified 6 months ago 2 times by WizardStan
Posted : 08/11/2023 11:08 pm
Neophyl
(@neophyl)
Illustrious Member
RE: Filament frequently gets stuck on ejection

You don't have any ramming or similar turned on in your profiles do you ?  Also is your machine a Mk3 only or does it have an MMU ?  Im not familiar with the orange part

Posted : 09/11/2023 7:15 am
WizardStan
(@wizardstan)
Active Member
Topic starter answered:
RE: Filament frequently gets stuck on ejection

It's got the MMU2. Sorry, I forgot to mention.

The only change I made to any of my profiles was increasing the first layer temperature of my filament when I got a textured bed, everything else is standard PrusaSlicer profiles.  I search for "ram" and the only things that come up are related to tool change for MM printers.

Now that you've asked and I'm thinking about it, I could be mistaken but I've done multicolour prints several times without issue, it's only when I select the "MMU2S Single" profile .  I'll need to do some experiments to verify, but if it's true does that help identify what the problem could be?  I'd assumed it was a hardware issue, but could it be my printer doing something weird when in "single mode" that it doesn't in "MMU mode" or whatever?

Posted : 09/11/2023 9:51 am
Neophyl
(@neophyl)
Illustrious Member
RE: Filament frequently gets stuck on ejection

I asked because the only way I can see filament bending like that is if its retracted and then fed back in and the tip hits something, causing it to bend.  On a basic Mk3 when you unload filament it just pulls it back so you can never get a tip shaped like that.  With MMU type printers they can ram the filament to shape the tip to make automatic loading possible to next time the filament is fed in.

I suspect there's something in your profile(s) that you are using thats doing that rather than a smooth unload.  As this is the MK3 forum and not the MMU forum you might get some more specific help if you post there.  I dont have an MMU personally but I'd start by saving one of your projects (File>Save Project As) from Prusa Slicer with the profile you are using.  That way people can load it and see ALL the settings you are using.  

Posted : 09/11/2023 10:32 am
WizardStan
(@wizardstan)
Active Member
Topic starter answered:
RE: Filament frequently gets stuck on ejection

It only ejects 2cm before ramming it back in.  I've taken a few videos and it does the little ramming you mention, just a couple cm, then pulls it straight out, some 8 or 9 cm and gets stuck.  When it works, this 8cm ejection is followed by a brief pause and then full retraction (I assume it pulls 8cm to clear the filament sensor).  I really hoped you were right, that it was just a matter of ramming parameters, but it doesn't push it back at all after this initial ejection so there's no way that could be the cause.

Thanks for your help, it did lead to more clues but no answer yet.  I'll take this to the MMU section of the forum.  It may still be related; maybe the ramming isn't giving the tip enough time to cool so when it ejects and hits the extrusion gear it just warps the soft plastic instead.  Working hypothesis, no idea how to test it though.

Posted : 09/11/2023 7:01 pm
Neophyl
(@neophyl)
Illustrious Member
RE: Filament frequently gets stuck on ejection

Thats why I suggest posting a project file 3mf.  That way people can see what all the settings are and something might jump out at someone.  Also the gcode can be output and could be examined to see the movements on that.  Sorry best suggestion I can do 🙂

Posted : 09/11/2023 7:17 pm
WizardStan
(@wizardstan)
Active Member
Topic starter answered:
RE: Filament frequently gets stuck on ejection

Yeah, I get that. I intend to post a small representative project to my other thread soon; I'm just doing some experiments first.  The biggest issue in my investigation is that it happens whether the print finishes or if I cancel it, so while I think there's a gcode fix I could come up with for prints that work fine, it's not a true solution if it still gets stuck when I need to abort a print that's fallen off the plate.

Posted : 09/11/2023 8:05 pm
WizardStan
(@wizardstan)
Active Member
Topic starter answered:
RE: Filament frequently gets stuck on ejection

I was right. After some gcode experiments I figured out the filament was still a little soft as it was ejecting.  As part of my experiments I also noticed that a lot of my filament was massively stringing as it was ejecting. Long story short, wet filament.  I opened a fresh vacuum sealed spool and it's printing and ejecting with no problems. I thought I'd been doing well keeping them in sealed containers but it's been a moist summer, which explains why it seemed to "suddenly" just start happening, and has been getting worse.

Posted : 09/11/2023 10:48 pm
Share: