Filament "bulge" at tip makes unloading filaments difficult
 
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Filament "bulge" at tip makes unloading filaments difficult  

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jlogoyda
(@jlogoyda)
Member
Filament "bulge" at tip makes unloading filaments difficult

This happens after every unload with both PLA and PETG, which are the only filaments I've ever used. My prints are mostly ok, but I have a decent amount of stringing, even with PLA. The bulge is large enough that the tip of  the filament really has to squeeze through the PTFE tubing after it has passed through the extruder; I really have to pull it to get it through the filament sensor, and it pulls the tiny piece of PTFE right off the end of the sensor because the filament tip gets stuck in the tube.

I can see through the PTFE into the hot end that the bulge is present during unloading before reaching the extruder, so the problem is definitely at the hot end somewhere. Repeated cold pulls with PLA at 270 degC haven't helped. Filaments are all in dryers for six hours before printing and also during printing, so I doubt moisture is an issue.

Any help would be appreciated! Sorry if this post is redundant; I don't know if this problem has a name, but it's certainly not "blob" based on my googling.

This topic was modified 3 months ago by jlogoyda
Posted : 06/12/2023 4:10 am
mark
 mark
(@mark-3)
Reputable Member
RE: Filament "bulge" at tip makes unloading filaments difficult

I'd suggest you replace the hot end PTFE tube if you haven't already:

https://help.prusa3d.com/guide/how-to-replace-a-hotend-ptfe-tube-mini-mini_119449

If filament is leaking out, you may have some stuck in there. Check steps 6 and 7.

The hot end PTFE tube is a known wear item. I have several on hand and replace them when needed.

Regards,

Mark

Posted : 07/12/2023 9:51 am
muhendees
(@muhendees)
Active Member
RE: Filament "bulge" at tip makes unloading filaments difficult

interesting. I have the same issue from day 1. never thought it is a problem lol. 

Since I have changed some flow path on my printer I have magnetic coupler between sensor and extruder and when I change filament I cut it to prepare for next use. 

 

Now you mentioned I am curious what is causing it. Maybe too much pressure from bowden tube bend?

I noticed that sometimes if you manually move X axis while nozzle is hot a bit of filament will come out. Since change filament or unload filament pushes a bit of filament before retraction I am assuming it is hotend issue. Gonna go do some experiments 

Posted : 30/12/2023 6:48 pm
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