MK3S PTFE tube in hot end keeps getting clogged by fussing to my PLA filament.

MK3S PTFE tube in hot end keeps getting clogged by fussing to my PLA filament.  

New Member

I've seen multiple post where the only solution given is to simply replace the PTFE tube. but as I had 2 of my tubes clog on consecutive prints, and I only have one more so I want to make sure I know why it's clogging before I print any more. 

here's a picture of the filament stuck in the PTFE tube. 

This issue started happening on my third print ( ). And both times it clogged it got about 1 hour into that print before clogging. 

My first 2 prints that both when near flawlessly were the pre-loaded g-code that came with my printer (3D benchy and adalina).

The only things that I can think of that might have changed are possibly the g-code, and room temperature.

I'm fairly curtain that I didn't change any of the default settings in PrusaSlicer, and have been using prusament PLA for all of my prints so far. I did find a video suggesting that if the retraction settings where to large, the gears where grinding into the fulfillment too much, and there is too many retractions close together there might be issue with the fulfillment sticking in the PTFE tube. ( ). I really don't know if this is actually the issue though, as his printer uses a somewhat different set up for extrusion. and the drive gear on mine doesn't seem to be eating into the filament nearly as much. 

Another idea I had is it's possible that since the temperature in my room was a little hotter (maybe 2 or 3 C hotter than the first 2 successful prints) both times when it failed, maybe I got heat creep and my filament was able to melt just enough in the tube to stick to the PTFE. But I really couldn't find anything else online that explicitly agreed with this line of thought.

It's possible that it's a combination of both those things, or I'm just complacently off of what the actually issue is.

I ordered some Capricorn PTFE tube, as many people suggest that it's better than the tubes prusa uses, and some people suggest using smaller retraction settings. 

do any of you have any other idea how fix this issue?


Posted : 16/07/2020 6:26 am
Veteran Member Moderator

Hi Tyler. did you slice this model yourself? 
Did you use 100% infill? (Probably not a good idea)     consider  using a lot of top and bottom  layers instead, you still end up with no gaps in the model, but don't have problems with the extruder over estimating how much infil filament is required for 100%
I get more blockages when I use the Default retraction settings (0.8mm with the Mk3) so I use 0.4mm for PLA and PETG.

Models with lots of  'long' retractions, tend to have difficulties  with heat creep. and then blockages

If I get a Blockage my first corrective action, is to heat the nozzle up to a higher than normal temperature, let it sit a while, then I grip the filament just above the extruder, and push firmly and directly into the  extruder,  this usually shifts the blockage without need for dissassembly.
If the filament breaks off under the extruder, 
I slacken off the bondtech idler door then  use a 1.5mm Alen key, to push the filament stub through into the nozzle

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 : 16/07/2020 4:03 pm

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