How to stop filament from tangling when it unspools?

[bbinnard]

My Atom2 delta-style printer works fine, but any time I make a print that takes more than about 40 minutes the filament gets tangled between the spool and the printer. If I don't untangle it by hand - which can be tricky and take a while - the extruder get stuck and the print is ruined.

I've tried having the filament spool both horizontal and vertical, on the table with the printer, and on the floor, and none of these options seems any better.

Am I missing some secret about unspooling filament in a way that does not cause tangles?

[3dkarma]

Is there any tension on the spool as it unwinds? If there's no tension, the filament on the spool can sometimes loosen and wrap over the free end, causing a tangle.

[bbinnard]

I think the problem was that the filament was simply wound too tightly on the spool. I'm on a different spool now and it has much looser windings. It seems like that looser winding allows the strand being pulled by the printer to pass over other underlying strands as needed.

On the other spool the active strand frequently got caught by another one that was lying on top of it, and the extruder gear was not strong enough to pull it free.