Filment Spool Jams

[SteedMaker]

I have a Rep 2 and finally I have the cable harness replaced, the build plate level, the tension on the filament gear adjusted just right, the models exporting and printing at hires.

However, now I have one last obstacle - the filament keeps knotting up when it comes off the spool and kills the print job.  I have about 10 large print jobs half done because of this problem.  It doesn't seem to matter which spool I use, I get the same problem.  See the image below that shows a typical problem.  ....and yes that is a cheap Chinese filament but I have had the same thing happen with Makerbot Spools.  I am sure I am not the only one who has experienced this.  What do folks do to avoid this frustration?  I have tried to babysit the spool and that works but if you leave for a half hour or more it will probably fail.

One of the things I did to avoid this was that I noi longer use the Makerbot Spool spool holder on the back of the printer, I have rigged a more direct feed using pvc piping - I think that helped but still I get far too many snags that stops the filament from reaching printer.  I think the spools are wound inconsistently and incorrectly.

Suggestions?

[Nagalfar]

If it is caused by yourself - e.g. gets entangled while switching -  you could use something like this:

http://www.thingiverse.com/thing:43220

to prevent entanglement while switching out your spools. This is the only problem I ever had with Makerbot PLA, but you can always disentangle them manually if it happens.

However if your chinese pla was already entangled during coiling there isn't much you can do, other than recoiling it manually. I wouldn't go as far as call it cheap quality tough. Infact if your picture shows glow in the dark blue we even use the same stuff - and mine hasn't had this issue yet.

[Wingcommander whpthomas]

Print a set of spool clips http://www.thingiverse.com/thing:43220 and clip them on the end of your filament when you store your reels. Stops the end from unravelling and getting knotted.

[Joseph Chiu]

I think most of us eventually develop good filament "hygiene" with experience and generally avoid tangling.  The first step is to keep the filament from getting loose on the spool or (worse) come off the spool.

If the filament does come loose, the filament will sometimes wrap under itself creating a knot which may not be obvious at first.  Sometimes, the knot will travel for a while until it eventually stops and causes the jam.

Whenever I do end up with a coil that has gone loose, I put my thumb over the remaining snug filament, and then despool the loose end completely, making sure to work free any cross-overs and twists.  Then I turn the spool to repack the filament snugly to the spool.  There should not be any gaps when you are done.

On Feb 2, 2013 1:13 PM, "Wingcommander whpthomas" <m...@henri.net> wrote:

Print a set of spool clips http://www.thingiverse.com/thing:43220 and clip them on the end of your filament when you store your reels. Stops the end from unravelling and getting knotted.

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[fredhag]

Ah, I've been waiting for this moment.  Yes, I am sure there are some spool jamming situations that could be avoided by prevention such as guiding/controlling the despooling path.  However, I have had a dozen times when the spool had been generally well loaded by the manufacturer (I was solely using MBI ABS but am now going to Octave, Jet, etc.), but there would occasionally be a situation where the plastic would cross over itself a few times in such a way that it jams up just like SteedMaker showed.  

Every time I start a new spool, i carefully unwrap about 20 loops of plastic to see how uniformly it's wrapped.  If I'm not confident, I will load the plastic into the printer and then briefly unwrap as much plastic as that job will need and carefully rewrap it onto the spool.  It's hard to describe, but I hold it in my hand similar to one would coil rope for a lasso (and occasionally wrap it around a back of a chair across the room or something like that to keep it from kinking), but it does need to be done carefully or it will twist around to form a knotted ball easily.  If I find a kink that looks like a knot while checking, I remove the spool from the mount and feed the spool through the loop of plastic that would eventually cause the jam and then rewrap.

I once had a really bad spool from MBI in which I unspooled the plastic directly onto an empty spool, like a reel-to-reel tape recorder or film projector.

Cheers,

Fred

[SteedMaker]

I find the cheap Chinese source every bit as good as MakerBot filament.  However, my experience has been that it is not me changing the filament -the problem is often a number of layers into the spool.  It is particularly annoying on large prints.  I am currently using a Makerbot spool and printing out a large print (been printing at hires for over 24 hours - probably has another 8 hours or so to go).  All it takes is one cross over like in the picture and the print fails well into the print not from slack in the first couple of levels of the spool.  The failures are often half way through a large print (perhaps 1/3 to half way into a spool.

[SteedMaker]

Fred,

I was afraid to hear of folks resorting to these kind of strategies to have a successul print.  I had one spool that was so bad every layer there was a crossover and I couldn't hardly print anything.   I had to unload it and I ended up cutting it up into smaller sections so it didn't twist on itself and will use the short lengths for small builds.

[Wingcommander whpthomas]

I purchased a spool from SainSmart, which had small cardboard flanges so I decided to transfer it to a plastic reel, only to discover it had a break half way through the spool that was just been taped together. If this had got into the extruder I fear it would have caused all kinds of problems - on top of causing the print to fail. The filament itself prints OK though. All the other spools I have purchased from BilbyCNC in Australia, and another local vendor have been faultless - so I think some manufacturers must be just sloppy if you are getting tangles mid spool.

[John Meiczinger]

I have the same problem. Have to check every ten minutes. Lost three prints from snags. Maybe a good design could be based on a fishing reel. There is a moving guide to pan horizontally back and forth. The line  (filament) is  "coached into position as the feed happens. This allows for fewer snags. I have not developed this but it might be viable.

On Saturday, February 2, 2013 3:23:23 PM UTC-5, SteedMaker wrote:

[Jetguy]

Sailfish firmware allows for an externally triggered pause function called P-stop.

This function can be combined with a number of sensors to detect filament issues such as a spool tangle and cause the printer to pause BEFORE the print is ruined by an air print.

Here are the hardware instructions to enable the function at the board level http://www.extrud3d.com/p-stop

Here is a printable set of STLs that can make a tension detector to detect when the extruder is trying to pull filament and the spool is jammed. http://www.thingiverse.com/thing:107775 There is the option to make it a motorized feeder as well but  that is not strictly required. I used optical endstops because a switch clicking for the feeder  could get to  be very annoying. http://www.amazon.com/SainSmart-Optical-Endstop-Printer-Makerbot/dp/B00EVOKHPO/ref=sr_1_1?ie=UTF8&qid=1391277417&sr=8-1&keywords=optical+endstop

There are so many sensor up on thingiverse, just start doing a search. Point being, the firmware supports an easily triggered pause so if you can detect the filament tangle before it makes the extruder skip or slip, then the print will be saved.

Alternatively, you can go fully mechanical, it just requires you set the menu up to be one button push away from pause after starting the print http://www.thingiverse.com/thing:81601

[Joseph Chiu]

You might want to see my video about tangling to see if it helps you: http://www.youtube.com/watch?v=lE9LchCtKL4

[Shawn]

I got hit by this some time ago. It is tooo easy to "chase" the knot
all the way to the end of the spool.

My solution is two fold.
1. Avoid behavior that leads to tangles. This means that I hold onto
the end of the filament when loading/unloading and ensuring the spool is
never allowed to "relax" without control (i.e. I don't let go of the end
of the filament and let it spin around the spool). When I am swapping
out filaments, I use the two holes conveniently on the side of the spool
rims to hold onto the filament (no need to print clips then) - All the
MBI spools I've seen has them.

The reason here is that if you let go of the end of the filament, it
unwinds itself as it relaxes. There is no guarantee at that point that
the end has not pass under one or more other loops of filament. If it
has, you will run into a knot at some point - usually hours or weeks
after this incident.

2. If/when I find a knot, I grip the knot so it doesn't slide around.
Then I unload the filament. Then I take the end of the filament and
pass it under the knot in the direction that causes the knot to become
untangled. Then reload and print away. If I take care with my filament
hygine (as so named in another response here), then I never have to do
this, or I only find one knot in the spool.

The important thing is to never let your filament unwind freely on the
spool. Since learning that I have never seen another knot. (though I
may just have been lucky thus far...)

My thoughts...

Shawn

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