How to prevent filament unwinding?

I have a problem with my filaments which try to unwind themselves during a print. As the extruder pulls the filament, it loses its tightly wound status and a few coils of loose filament detach from the spool, then they get tangled. I have to manually correct these problems. Is there a solution which would prevent the filament from getting loose?

Thanks....

I had this problem a lot when I first started out. First thing, if your spool holder has bearings? Dump them... You need some friction. Second design or download a spool holder that has a arm that helps prevent the issue (see photo attached). Also using a feed tube mounted near the spool holder that guides the filament up can also help. These 3 things together totally cured my issue with finding my machine wrapped in loose filament when I would leave the room for a few minutes.

The best spool holder i made so far features bearings, but also a PTFE feed tube that is pressed against the spooled up material with a spring. This keeps the spool from spinning freely while minimizing the force needed to pull the filament. It also helps against entanglement.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Do you have a picture of this setup with the PTFE tube? I'm having a hard time picturing it in my head.

Thanks!

My corexy printer has a spool holder with bearings, so it does tend to unwind. I designed a little peg that is screwed to the extrusion a little way away, and this has a strip of foam glued onto the flat side that drags against the edge of the spool. Not much friction, but just enough to stop the filament unwinding. The nut allows me to adjust its position for different-sized spools.

I've attached the files, in case it helps...

Edited 1 time(s). Last edit at 04/23/2016 06:19AM by David J.

There are a number of 3D printable files on places such as thingiverse that help to prevent this. Although, like mentioned above, we find that a bit of resistance on the spool holder works great (so the spool cannot move very freely). Seems to work for us.


Cheers,
www.3dexfilament.co.uk

It can be as simple as having your axle uneven in height so that the spool slides to one side and rubs on the arm.