Turns out mig wire birdsnesting is a thing in 3D printing too

[skotl]

My filament keeps crossing over, pulls taught and then snaps.

It's ok while I'm there to look out for it but I can't leave it for more than 10 minutes in case it happens again. Fallback plan is to unwind the spool a bit and leave it loose on the floor

Two questions:

1. What causes this - is it something I'm doing or is it down to poor quality filament?
2. Is it saveable? I know that if this happens to a mig wire spool you have to bin it as there's no way to reliably fix it - same with PLA?

 

[ChrisBailey]

This usually happens when the filament is poorly wound at manufacture. It can also happen if you let the spool go loose and unwind.

You can re-spool it, its just a faff. Also, the filament shouldnt easily snap. Ive only ever snapped the crap filament that came with my ender 3 and a spool of eSun PETG when it went brittle after I dried it in the oven.

Chances are the filament your using is past it.
I can recoment ERYOne filament, its about £20 on amazon and is wound nicely (one of their own advertisements).

 

[Screwdriver]

Chances are, it has only ever crossed over once (probably when you first opened it) and since then, the crossover will just keep travelling back into the spool as it unravels.

It's probably too late looking at the picture but the only way to uncross a spiral is to find an uncoiled section under the loose end and keep that tight while respooling.

 

[Dev]

I buy the cheapest I can find filament and out of the dozens, maybe hundreds I’ve had a badly wound roll a handful of times. You’re not letting the end get loose are you? You can never let go of the free end once you’ve opened or it’ll loop under itself like you’re describing. When you unload keep a hold of the tip and most reels have a couple of holes in the side wall for you to tuck the end in to stop it unspooling.

If you are doing that fastidiously then yes maybe you’ve been unlucky and got a dud roll. if it’s just that one my Advice is save yourself the aggravation and chuck it, life’s too short.

 

[carbon]

How are you supporting the reel when in use and how is it fed to the extruder?

 

[m_c]

I buy the cheapest I can find filament and out of the dozens, maybe hundreds I’ve had a badly wound roll a handful of times. You’re not letting the end get loose are you? You can never let go of the free end once you’ve opened or it’ll loop under itself like you’re describing. When you unload keep a hold of the tip and most reels have a couple of holes in the side wall for you to tuck the end in to stop it unspooling.

If you are doing that fastidiously then yes maybe you’ve been unlucky and got a dud roll. if it’s just that one my Advice is save yourself the aggravation and chuck it, life’s too short.

This.

There is only way to tangle a roll, and it's not by how it's wound. The winding machine can't miraculously tangle the roll when the filament is wound on to the roll. It can only be tangled by the cut end being passed under another winding. Yes, that could potentially happen when the filament is cut-off during manufacture, but I'd very much doubt somebody doing it for a living is likely to make that mistake. Plus it's very easy to notice if you look at the final wrap before using a new roll.

I've only ever had a tangle once, and it was my own fault, because I let the loose end go while loading the filament, and foolishly never checked it hadn't got crossed over as I was in a bit of a rush to print something. I then had to spend the next hour babysitting the printer and moving the tangle about.

 

[Screwdriver]

Two questions:

1. What causes this - is it something I'm doing or is it down to poor quality filament?
2. Is it saveable? I know that if this happens to a mig wire spool you have to bin it as there's no way to reliably fix it - same with PLA?

From a topological perspective, a tangled spiral can be a nightmare, we've all played with a slinky...

If it is tangled or crossed over and not just poor alignment which I think @skotl is suggesting then it is most likely something you did.

I say that because it would be impossible to "cross over" a filament as it is being wound onto a reel. Both ends will be constrained so there's no way for one loop to cross over another. This is assuming they did not mess it up when the end was cut and poked into the reel. I look for that possibility when I first open mine. I stick a thumb on the main body of the reel to stop it unraveling and allow the free end to do whatever it wants before I snip off a bit and poke it into the printer.

If the free end goes under a loop on the main spool before you constrain it, that cross over point will migrate backwards down the spool as it unwinds. If you think about it, as soon as there is any loss of tension, the free end will lift up away from the spool which also lifts the crossed over loop. The crossover point will automatically slide away from the free end, back down the spiral. It will keep doing that too because once in a while it will jam and to unjam it, you have to release the tension which allows the crossover point to migrate etc. etc.

If you can't be bothered to salvage it (you may need to rewind it and dry it) then I'd be happy to buy it off you for the price of postage. You'll probably need to clean any dust/hair off it too. If you can't use it on the printer, I recommend (sending it to me!) getting yourself a 3d pen.

I was too busy waffling and @m_c beat me to it....

 

[m_c]

The whole badly wound thing is something that annoys me.
It's regularly trotted out on 3D printing discussions, usually by those who regularly get tangles, yet they can't explain how it's possible to badly wind a reel.

 

[skotl]

Cheers all

So it's almost certainly 100% my fault then. To be honest it never occurred to me that you would need to keep the spool pretty tightly wound - obvious in hindsight but this is my first spool and I've just been treating it like a box of cornflakes.

I'll continue with this one along the carpet until it annoys me too much then I'll fling it in the bin and take better care of the next one!

 

[Screwdriver]

Cheers all

So it's almost certainly 100% my fault then. To be honest it never occurred to me that you would need to keep the spool pretty tightly wound - obvious in hindsight but this is my first spool and I've just been treating it like a box of cornflakes.

I'll continue with this one along the carpet until it annoys me too much then I'll fling it in the bin and take better care of the next one!

Fling it my way if you do.

But yes, you absolutely have to keep it under some small degree of tension at all times. There is a compromise between having a reel so tightly bound it interferes with feed and having it so loose it unwinds itself on the spool. It's a bit like a clockwork spring in some respects, once tension is released, it loosens everything, everywhere, all at once...