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UM+ feeder scratches filament

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ok coming from the extrusion upgrade thread, here more details about my scratching problem:


When looking into the feeder from the top hole (where the bowden tube goes in ;) ) I can see that the knurled wheel is in the path of the filament. This basically makes the hole D shaped like the left straight side that should be round is occupied by the wheel (I will make a picture later, the printer is currently running).

So, even when the tension wheel is fully out of the way my filament gets scratched by the wheel.

Maybe mine is slightly too large?!

I measured my filament and it is in spec (2.82-2.85 but never over that).

I noticed that before taking it apart - and the knurled wheel is completely fixed in its position so it can not have moved by accident.

Are there specs for the knurled wheel so I could measure it and compare? Or does mine have too sharp teeth?!

Any ideas?



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Your knurled wheel should create the motion, does also scratched your filament or is it the wheel that supplies the pressure that pushed the filament against the knurled wheel?

Have you tried opening up your feeder?

That 'pushing-wheel' should be secured between two arms. Could you check if that wheel can still rotate freely and if those arms are still correct?

Perhaps by adding a picture of what the inside of your feeder looks like it could pinpoint us into a certain direction. Thanks!

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Pictures? - I have a video! :D

It is the knurled wheel - I removed the idler wheel + lever ;)

So you can see, that I can move the knurled wheel by just moving the filament (which I tried to straighten as best as I could) - if i hold it tight, as it would be from the stepper I can scratch it - if you crank up the volume a bit you can hear it in the end.

As my filament is normally curved, bowing to the right when it comes from the roll - it would press even harder onto the knurled wheel.


(It is a public but unlisted video, I hope that works)

So overall it is no deal breaker (for me) and as far as I see it not "solvable" in this iteration but I wanted to mention it.

Edited by Guest

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