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filament breaking accidentally

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Hi guys,

I´m printing on an Ultimaker 2 since four months now.

For about three weeks I have problems with the filament breaking repeatedly.

I found this:



But ist doesn´t help in this case. The used filaments are Ultimaker PLA silver (that came with the machine) and Verbatim PLA white. Both filaments show the same behaviour.

Most times the fimanet breaks inside the bowden tube. Two times it broke just before entering the feeder. After unfeeding the filament, there is a length of about 20-30 cm where it is hard and extremely brittle. You can break with one finger and it makes a cracking sound.

So I break away the brittle part, feed it again and it works for some time (between half an hour and about 4 hours). Then the same: filament breaks and again a section of brittle filament after the break.

On the first spool of filament (Ultimaker PLA), it started with about one third of the filament left. So I thought, this happened due to the lower diameter towards the center of the spool.

But after changing to a new spool (Verbatim PLA), it happened again after about four hours of printing. The Verbatim filament was packed in a sealed bag with desiccant. I unpacked it just before printing, so it was dry.

Both filaments have a certain length of brittle material. It´s not the whole spool. And as this happens accidentally, I have no idea what is causing the problem.

Can you help?

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I will test PLA-HT from Colorfabb. Waiting for delivery now.

After some testing with the white Verbatim PLA, it looks like the problems have something to do with retraction.

Printing this small thing always causes breaks of the filament inside the bowden tube.MiniCalTestDRJS25022015.jpg.4c4f151c869ce81052f7eda7127f54d9.jpg

During this print the printer retracts very often in a short time. This means that the same section of the filament is moved forward and back several times.

It was not possible to see which print layers cause the break. Because the filament doesn´t break inside the feeder, but later in printing inside the tube. So I marked the filament with a color marker.

It showed that the filament breaks where the printer had done retractions before. The solid bottom does not cause the filament to break. I tried to print some other things without retraction, even a big square at full bed size. The filament never broke.

That´s why I think there is a relation with (much) retraction and filament breaks.

Most parts that need to be printed are small and need a lot of retraction. Adjusting the feeder tension did not change anything. So far, I hope the colorfabb filament will be better to print.


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How old is the filament? I have had problems from Colorfabb filament that was old and had gotten brittle. I had ordered some filament and it came from an old batch from the supplier. They had it in their warehouse for almost a year apparently before shipping and I was able to confirm with colorfabb about the production date . It snapped repeatedly as I tried to use it and Colorfabb sent me a new roll. The new roll printed with no problems.

Edited by Guest

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Ultimaker had a problem with their filament last summer - mostly it's all better now but the problem is it ages much too quickly and gets brittle.  I recommend you get your money back.

A basic test - take the filament still on the spool and bend the end 90 degrees.  If it breaks consider throwing it all away.  I still usually print with it but at some point (breaks at 20 degrees?) it will start breaking in the bowden.

You could turn off *all* retractions and probably still use the filament but only for very simple prints.

Ultimaker's newer filament is fine.  And filament from 2014 is fine also.

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You don't need to check this. It's not your responsibility.

Normal filament does get more brittle with time but I have filament 2 years old that you can bend 90 degrees with your fingers and it doesn't break. A little more bending and it snaps. Brand new filament can be twisted in a circle and it's fine. If the filament is snapping in the bowden and it is less than 6 months since purchase it seems to me the seller should refund you for this or the portion you haven't used yet or send you some free filament. There was a known problem with UM filament (now fixed) so I would expect the seller/store won't be too surprised if you complain that the filament was too brittle. I can't speak to Verbatim filament quality and problems. I didn't even know they made filament.

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Thanks gr5 for the information on UM filament.

There is no Ultimaker PLA filament left. I used the rest of the spool for testing.

Verbatim filament is quite similar, but the prints show uneven color distribution on surfaces.

On youtube there is an interesting video for testing filament.


I tried this, too. And noticed the same filament-breaking-behavior.

The filament starts to break after some time after stretching. So, I always unfeed the filament after printing. Until now, it works. Even on a large (140 grams) print.

Of course, this can´t be a solution of this problem. This just lets me use the rest of Verbatim filament.

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