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Filament snapping in feeder S5 Carbon Fiber Nylon BASF PAHT CF15

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Posted · Filament snapping in feeder S5 Carbon Fiber Nylon BASF PAHT CF15

The material is new, the feeder is not too tight from what I can tell. It did fine for the first half of the roll, but it seems now that the material is snapping when the feeder forces it more strait because the material on the spool has a smaller radius as the spool gets lower and lower? I keep my spools in a sub 15% humidity room, but the room is also my print room and so it gets hot, between 95 and 100F normally. I dont generally have a spool for more than a month. The BASF PAHT CF15 that is giving me issues I have had for less than 2 weeks. again, it did about half the roll with no issues. I have tried to put the roll in my material dryer for 24hrs and no change I can notice, so I don't think it is moisture. 

I got a brand new roll in yesterday, just to be sure it responds the same...I expect it will do fine the first half then start breaking also?

Any ideas?

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Posted · Filament snapping in feeder S5 Carbon Fiber Nylon BASF PAHT CF15

 

In PLA-based filament it is known that microcracks can grow if the filament is bent or stretched (thus kept under a load) for a longer period of time. So, don't let material sit still in the feeding-traject after the print is finished, but unload the spool immediately.

 

Some materials also get brittle due to changes in crystal structure, becoming more crystaline (often reversible), and due to moisture absorption and damage (not reversible as far as I know). Both happen in PLA.

 

Keeping it dry obviously helps against hydrolysis. But I am not sure what the best solution is for "un-crystalisation"? Melting should help, but then you lose your filament. Heating up to the point just before deformation might change its molecule structure in both ways: making it soft again, or rather making it harder (encouraging crystal growth), similar to post-curing and annealing. I don't know which one wins. And your warm room might speed-up these effects?

 

I don't know your material, so I have no idea if it is affected by these phenomena.

 

Try what the effect is of heat on a few short pieces of this filament.

 

Keep in mind that when heating it too much above its glass transition temperature, it will shrink in length, but get thicker (e.g. from 2.85mm to 3.10mm), and then it may no longer fit in the bowden tube or nozzle. You could also try unwinding it manually, and manually straightening it a bit, after which you release it again (to stop crack growth), so the bending radius is not as tight as before. Then it will get stressed less in the feeder. It may take trial and error.

 

It could also be a bad batch or spool, or a filament that is very brittle by nature, especially if it is a filled filament.

 

Pictures:
Microcracks in PLA/PHA filament after straightening it, and then releasing it again, so the stress is off. If the bending stress would be kept on, these cracks would keep growing until the filament would break.

DSCN5649.thumb.JPG.6bbdd1ca1552266ce1b66269de7edea5.JPG

 

DSCN5654.thumb.JPG.8d711ff4f62ff3d1d91eaee3b0ffa713.JPG

 

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Posted · Filament snapping in feeder S5 Carbon Fiber Nylon BASF PAHT CF15

Any other thoughts? For now I am going to try and re spool the material into a much larger spool so that the radius is larger. this stuff is so so stiff and brittle. I tried heating it up to 200f and it was able to bend to about 5 degrees before snapping. Its almost like it needs an inline heater to bring it up to 250f before it goes into the feeders (both the feeder behind the machine on an S5, and the hot end.)

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