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I have a Tevo Tarantula, the problem is that PTFE is getting pulled back to the extruder gears and stopping filament extrusion, do you know how to solve this?

Image:

Extruder gears

One hypothesis I have is that there is a cooling problem in the hot end while a retraction is made, causing the extruder motor to pull the PTFE in it.

Suggestions appreciated!

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    $\begingroup$ To be clear, which PTFE tube you are talking about? The one on top or the one in the heatbreak near the nozzle? You are talking about pulled back, so that suggests the PTFE liner in the heat break, the upper PTFE (Bowden tube) is pulled forward. $\endgroup$ – 0scar Oct 24 '18 at 13:29
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You are probably right, I have a Tarantula as well, and this happened many times to me. The reason is mostly because the hotend fan gets too hot, stops working, then, the filament in the aluminium heat sink melts and sticks the filament inside the PTFE tube. Then, on the retraction, the PTFE is pulled into the gears just like on your picture. Also, the filament stops getting extruded a few moments later.

One solution for that was to buy a new PTFE tube with a pneumatic connector that doesn't allow it to slide into the gears. However, the diameter of the screw thread (of the one that I bought) was too large, so I had to design a new static block for the extruder to fit it.

I chose this type of 1mm PTFE teflon tubing from aliexpress for my replacement.

Maybe you can find a pneumatic connector with the proper diameter.

However the real solution is to check why the heat sink is getting too hot. I bought a few other fans and printed an additional support for them on the hotend and I am making sure the fan stays on all the time.

I hope it helps!

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    $\begingroup$ good answer. there is to chance to get hot filiament in default Bowden setup. The provided fitting is just a bad quality - so need to be replaced. I also was cutting down the PTFE to allow a better grip $\endgroup$ – profesor79 Oct 24 '18 at 9:38
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    $\begingroup$ Just a little make it nice, and nice it is! $\endgroup$ – Trish Oct 25 '18 at 7:46

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