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[Solved] Filament Fails to Eject if Spool is Run Empty  

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TwoBallScrewBall
(@twoballscrewball)
Trusted Member
Filament Fails to Eject if Spool is Run Empty

New issue on one of my MK3s+'s. 

If I have a print running and the spool runs out, the printer can not eject the small piece of filament that remains in the extruder.  

If I run an eject before it runs out, everything is fine.   But if I let the end of the filament enter the extruder and trigger the IR sensor, it fails to back that little piece out, even if I am sitting there and immediately unload the filament as soon as the printer alerts to do so. 

I opened the idler door as instructed and tried to pull it out with pliers, but it would not move, and I was afraid to break something because of how hard I was trying to pull. 

I can get around this by force feeding a new piece of filament into the extruder, which displaces the small section that remains when a spool runs out.  

Any ideas?  I did have to recently hot-tighten the hot end after getting a leak at the heat break / heat block joint.   No leaks now, but something is causing these eject failures. 

Thanks!!!

Posted : 15/06/2021 4:16 pm
fuchsr
(@fuchsr)
Famed Member
RE: Filament Fails to Eject if Spool is Run Empty

Happens to me on a regular basis, with some filaments more then others. They tend to be a bit bent at the end so the filament can't move back. Usually it requires me to open the idler door and use needle nosed pliers and a lot of "persuasion " to get the stuck piece out. 

Posted : 15/06/2021 5:09 pm
TwoBallScrewBall
(@twoballscrewball)
Trusted Member
Topic starter answered:
RE: Filament Fails to Eject if Spool is Run Empty

So I was swapping in a new heat block, nozzle heatbreak and while I had the extruder apart I got to looking to see if I could figure out why I was having ejection issues when the filament end entered the extruder.   Since the sensor is tripped by that little captured ball up near the top, the issue had to be either in that little square black piece that holds the ball, or with the sensor cover plate.  I had already removed the sensor cover plate and still had this issue with failure to eject, so I knew that was not the issue.  I got to looking at the piece that holds the stainless ball, and the upper and lower holes that the filament pass through were a bit irregular, and when I manually ran filament through that part it would sometimes get stuck.  

 

I carefully took a #40 drill bit (just under 2.5mm) and cleaned up the holes in this piece by hand, carefully spinning the bit and reaming out the holes.  I made sure to run the bit through both holes to make sure I maintained good alignment.   Got it all back together and did a few test prints, where I snipped the filament just before it entered the extruder, let it trip the sensor, and I seem to be having 100% success with ejects now.   

I wish I took some photos, but I kind of did this on a whim.   I will be doing this to my other printer, as they both have / had this same issue, so I will take photos when I do that and post them up. 

Hope this helps someone!

Thanks. 

Posted : 27/06/2021 4:02 pm
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