This should be obvious. But it apparently isn’t.
This is a hastily produced video. A rough draft, if you will. Please comment. I will make a nicer version incorporating the feedback. Thanks!
http://www.youtube.com/watch?v=lE9LchCtKL4
One of those “duh” moments. I have had this problem in the past with wire/solder, i just struggled with it. Now i will fix it… Thanks.
Oh, yes, I’ve had that happen to me with solder countless times. With solder, it’s soft enough that I just “snap” the solder at the tangle, and then pick up the new end on the other side of the crossing. One customer reported having repeated tangling until the filament snapped on the spool, and then no more tangling. I’m quite sure that’s exactly what happened.
I think i have a spool at home that is in this state, unfortunately the spool is also just really bad plastic,
I’d love to have you test this out and report back! Sadly, I don’t have a cure for the quality, except to recommend our products! 
Great simple fix. Beats the times i chased the knot around the spool for an hour.
This should be a google helpout
3mm filament is a lot easier to deal with than 1.75. It has a bit to do with the fact a larger diameter is more rigid and the flexibility of 1.75 makes knots able to get really deep in the spool. prototype supply has never knotted from a new roll except one, yet I was told up ahead of this when buying from their discounted section. Luckily I caught it early and did a technique similar to this video.
None of that will happen if you use:
http://mauk.cc/webshop/systems/cartesio-tools/filament-1.75-pla-inside-reel-reprap
@Jos_Scheepers , if a line crossing was introduced, it would jam in that holder, too. It would actually be more difficult to unknot the tangle in it, IMHO.
Agreed, almost every printed holder I’ve seen is more counter-intuitive than a smooth turntable and a good storage routine.
Someone uses a wire holder mounted on the side as he is storing his filament role?
@Joseph_Chiu
A line crossing is actually not possible in this design. the best way to discribe what is happening is a ball of twine, where you start at the inside of the ball and not the outside.
Well, if you take a core-less spool and load it properly into that holder, you won’t get a line crossing after set up. But by the same argument, if you take a conventional spool and load it properly, you won’t get a line crossing there, either.
The point is that line crossing can get introduced accidentally while loading and unloading spools.
I’ve seen ball of twine get messed up (see https://www.google.com/search?q=yarn+barf&tbm=isch)
I’ve also seen CAT5 cables from a inside-payout spool get messed up when someone messed with the spool.