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End of spool gets stuck on Bowden tube  

End of spool gets stuck on Bowden tube

Hello Prusa Forum,

I’ve been attempting to use the “spool join” feature, which lets you use up all of one spool and continue the print with another spool automatically, with success on the hardware side of things.

However, a few times now, the little bend in the filament at the very end of the spool (that anchors the filament to the spool—see photos) has gotten caught on the end of the Bowden tube, and the extruder is unable to overcome this by force. This leads to the filament getting stuck in a spot where the filament sensor is still activated but the filament is not extruding, causing failed prints.

I’m wondering if anyone else has experienced this issue before (MMU or not) and if you’ve thought of or can think of any solutions to this problem, preferably that don’t involve manually cutting or bending the end of the filament roll every time. I’m thinking maybe there’s a way to create a funnel shape to make it easier for the extruder to pull the filament into the Bowden tube by force, or maybe the solution could be similar to how Prusa chamfered the inner edge of the mini Bowden tubes inside the MMU3.

I have a Prusa MK4 with the MMU3, so far the main issue filament has been Elegoo’s PLA but it has happened with various other rolls as well. Note that I had to recreate the photos, they’re just to illustrate the issue.

Thank you in advance!

Posted : 20/06/2024 10:04 pm
Veteran Member Moderator
RE: End of spool gets stuck on Bowden tube

The bend in the end, WON't Go away...  I try to cut it off before the printer gets to it...

On 3DQF Filament rolls they have the end of the filament visible, on the outside of the spool, so you can cut it off when you first open the roll, and then the filament pulls off the roll, at the end without issue. 

If I don't know what the end of the roll is like, and it's going to attempt to change whilst I am not present, I Cut the filament on the nearly empty spool to force a filament change whilst I am present, then I re spool the nearly empty spool, so that I can cut the end off and make sure there is no bend, then do another spool join when the new spool is near the end... 
Yes, it's more messing about, but you don't  lose a nearly complete print... 

regards 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 : 20/06/2024 10:59 pm