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Bowden tube + hot end Alignment

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Hello Forum,

im having Issues after changing The PTFE coupler. a few days ago, i had some underextrusion Problems with my U2, so i took all the hot end apart, in order to replace that Teflon part... all now is working perfectly and the prints are really awesome even at high Speeds... the issue im having now (despite putting all the hot end parts together carefully and following the assembly Manual - and some other observations taken from this Forum) is that when loading material, it doesnt gets inserted through the PTFE coupler properly, and get stuck, so i Need to move the bowden tube and some how try to make it straight to get the material loaded properly, then i hear a sound like, "clack" and the in gets trough the PTFE coupler. It is something like the Filament hits the ptfe cupler on the top, on the border of the PTFE conduct, and doesnt get into the hole... somehow not perfectly aligned...

so i took all again apart... and checked twice... but still im having this Problem... BUT, i use a sharp blade, and i make the Filament pointy, then it works like a charm... it doesnt get stuck.

does anybody has an idea about what can be happning?

Many thanks...


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I have sometimes heard the "clack" also and had to wriggle the tube to get the filament in. Now I always sharpen the filament edge. No issues since that. and I get 10/10 from the speed torture extruding test so I don't think my coupler is especially deformed to restrict the movement.


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It is because the Bowden tube is not fully inserted into the Teflon top!

This is much more fiddly than one would imagine!

WHen not inserted fully, the filament crashes into the 6.35mm "plateau" near the top of the Teflon coupler.

This must be without gap!


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I think a lot of people, UM printers or not, cut a point on the filament to help get the filament threaded through the various parts to the hot end. I have never investigated but if you consider firstly, the very little bends filament can have, plus the curve within it especially if from a reel, and secondly that within the printer design the "holes" that the filament needs to feed through will only have so much leeway on a 3mm measurement, then cutting a point can only help to get a smooth pathway.


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Thanks for your answers!

before the PTFE coupler change a pointy tip wasn't needed... so i think something is wrong... because now in need one... and Swroddriff, my bowdentube is fully inserted... it still moves up (but still clamped with that white four thoothed piece) that white part moves with, i think it was the normal behaviour of the machine when i got it from the manufacturer...


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REALLY close! Some bad-asses here even do it like this:

Loosen the 4 long vertical screws holding the head-assembly a little!

Then, while keeping a keen eye on the area top of teflon coupler,




holding the clip socket ring DOWN so the tube can move freely


-carefully move the bowden up and down while looking until you are


the tube is inside the Teflon receptor.


holding the tube down quite forcefully,

tighten the 4 vertical screws..not too much,

with a "childs hand". and slide the ring down and enter the horseshoe to

keep it there.

(some print out a fatter horseshow.. you find it in youmagine, but I never

needed one)



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+1 to Swordriff' last comment - I do this every time I re-install the bowden tube as I usually do an "atomic" clean after each filament change. I think the end of the bowden tube wears where it is gripped by the white part (which has metal blades inside to grip the tube)

You can always cut a 8-10mm of the end without this causing a problem

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