UM2 filament feeder tension

[axsdenied 0]

What is the correct tension for the filament feeder? There is conflicting information on the Internet and also there is talk of different feeder models requiring different tensions.

My printer is about 2 weeks old and the white tension pointer is in its top-most position (I never changed it). When the filament goes through the feeder a series of "marks" can be seen on it, as in photo (click on it to zoom in to see what I am talking about).

I am suspicious that the tension is too high but I would expect a new printer to be setup correctly???

Also in the photo you can see how the filament got ground away so the feeder could not grip it any more. This happened twice so far.

- First time when I was trying to print something with lots of retractions so I could kind of see how it happened as the filament was moved forwards and backwards a lot.

- This time it was just a solid block that was printed, no retractions. The printer was not used for 4 days and now I came to this. Could the tension be so high that the pressure weakened the plastic in 4 days?

Thanks for any help.

 

[takei-naodar 0]

If the pressure is to low you will get slipping marks as in your picture because the grip will not be strong enough. If the pressure is to high the filament can be deformed or you will get the motor skipping back all the time.

But i have to remark it has been long since i used the original Feeder... i now use mine with a MK8.

 

[axsdenied 0]

Can the depth of the "tracks" on the filament be used as a guide for the right tension?

What about when changing filaments and then going back to the original filament? Do I need to discard the section that was already in the bowden tube and that has "track" marks on it? Can the feeder have a good grip on already used section?

I am getting occasional clicking from the motor skipping and some underextrusion. I also had to clean the bowden tube from the small pieces and strings of PLA.

 

[takei-naodar 0]

Hmmm if you allready had occasional skipping it could well be that the filament had deformed while the printer was unused.

 

[donmilne 2]

Can the depth of the "tracks" on the filament be used as a guide for the right tension?

 

With practice, yes they can. In my experience (and I'm really only talking about PLA here), the right tension leaves a well defined knurled pattern in the filament, but the filament roundness is not distorted, and the feeder is not skipping (in cases where the tension is excessive, the feeder motor will have trouble even pushing the filament through the feeder.

 

[12th-man 0]

I have played with my tension for the filament. I found this article for making a new tension-er. I haven't tried it yet but it makes sense.

https://0x7d.com/2014/07/improved-ultimaker-2-material-extruder/

 

[donmilne 2]

That belt drive is a little "advanced". I wouldn't go for that just yet (not until it has proven itself with many users). Those of us who replace the stock feeder tend to go for Robert's replacement, found here: https://www.youmagine.com/designs/alternative-um2-feeder-version-two.