# Gnarly filament: just one of those things, or grounds for complaint?

everyone.

I'm a relative newcomer to 3D printing, so I don't know what constitutes an unacceptably bad spool of filament.

About 1/6 of the way into a roll of PETG (and maybe 4 hours into a 6-hour print), an over/under wrap brought things to a screeching halt. I aborted the print, then snipped the filament and started unspooling it, looking for more cross-wraps. I found a ton of them, along with a ton of kinks.

I stopped about 1/3 of the way into the spool, still finding kinks and cross-wraps, and said to heck with it. The only way to use it would have been to run the entire length onto another spool, carefully avoiding cross-wraps, and hope the kinks wouldn't affect the print quality.

I complained to the supplier but never even got a reply, so now I'm wondering if this is just one of those things I can expect from time to time. Any thoughts & opinions would be much appreciated.

Cheers,

Glasseyed

Filament should come off of the roll without overlapping itself. That being said depending on what you paid for it would determine if you should complain. Normally you get what you pay for. If you paid \$10 for it, I would think that is why it was so cheap, but if you paid >\$25 it should be nice stuff.

• I paid \$35 CAD per kg, so it's not ultra-premium or bargain-basement stuff. The fact is I've been quite pleased with the other filaments I've bought from this supplier, but the lack of response to my complaint made me determined not to buy from them again...until I got to wondering if this kind of thing is only to be expected every now & then. – Glasseyed Feb 14 '16 at 3:49
• I would go and complain. Worst case is that nothing happens, best case is you get new filament (and get to keep the bad roll too). – Eric Johnson Feb 14 '16 at 5:07
• @Glasseyed It could be just a fluke thing, but you should contact your supplier for this sort of thing (so long as it is not user error). You're paying for their standard quality, if you're not getting that, you deserve either a replacement or a refund. – tbm0115 Feb 16 '16 at 7:12

Sorry to say it, but MOST wrap-unders are caused by end-users releasing the free end of the filament when handling the spool. It is mathematically impossible to introduce a knot during initial spooling, and all the reputable filament vendors these days have pretty careful free-end control when the spool is taken off the spooler and sent to packaging.

Where you may get knots straight from the filament vendor is if they're respooling very carelessly and let go of the free end. You should only see this with very cheap filament.

So, it's possible that your vendor messed up, but you should probably rule out your own handling practices first. It's not hard to prevent losing the free end. The nicer spool styles these days have holes on the side-flanges for securing the free end during handling/storage. Or you can print one of many, many filament clip designs from Thingiverse or your favorite model site.

If you're very careful with handling and still get knots, switch suppliers. Anyone sloppy enough to repeatedly mis-handle new spools is likely also using extremely cheap material, and there have been a lot of anecdotal reports of very nasty industrial chemicals being mixed into the colorants of low-cost filament.

• Thanks, but user error wasn't responsible in this case: not only were there lots of other crossovers deeper into the spool, the filament was wobbly/kinky in a way that suggests problems with the take-up mechanism at the factory. – Glasseyed Feb 14 '16 at 3:56
• Crossovers very often work their way down as the spool unwraps. A knot can slip and slip and slip for hours and then catch and wreck the print. Not sure what you mean by wobbly/kinky? – Ryan Carlyle Feb 14 '16 at 4:00
• As if someone had flexed the filament every couple of inches, putting a slight bend in it. Probably nothing too serious by itself, but it tends to reinforce my belief that there was a problem with the take-up mechanism. As I said in my comment to Eric Johnson, I've been quite pleased with the other stuff I've bought from them. Maybe I'll just re-spool the remainder when I have an empty spool kicking around ( did I mention I'm a relative newcomer? ;-) Cheers! – Glasseyed Feb 14 '16 at 4:29
• Little wobbles can happen as the warm filament rolls over previous wraps and jumps from groove to groove. Bigger bends might mean they re-spooled off a drum that had a core that was too tight. Hard to say. – Ryan Carlyle Feb 14 '16 at 4:57

Knot happens when you loosen the filament yourself and then leave it like that or try to manually re-spool it. To avoid this kind of situation as well as the curly filament coming off the spool and getting tangled there, try to not loosen it and also build or print a "spool guide" for your 3d printer: http://www.thingiverse.com/search/page:1?q=filament+spool+guide&sa=