Hobbed bolt eating filament in the middle of printing

Over the weekend my daughter wanted to print something for a friend of hers. I said fine, but I want you to either model it yourself or find a model on your own... Trying to teach her to either want to model it on her own, or at least do a search for it. She found what she wanted and come to find out it was a Tardis. Matter of fact a pretty large one.... Ok what ever she wants. I showed her how to use the slicer program and get it all ready. Then when she did, I went in and checked on the printer, made sure it was all set up, and told her to be prepared as it would take it quite some time to print it, and to be ready to sit in there for some time. She just grabbed a book, and said ok. I showed her how to go in and make sure everything was hot, then make sure that the Z distance was ok. Everything seemed fine. She then loaded the file via the card. She got it started and I looked at it. All appeared fine to me so off it went. It ran for the entire book she read (About 4 hours) and then she had me check on it, and she grabbed another book in the series. She is a reader. She went in and read it all as well. She was on a roll. All printing looked good to. She said she was hungry so we went in, made dinner for the family and ate dinner. It had been running fine. Then we wrapped up for the night and I planned to just let it run. I would check on it off and on, and it was doing great. Then sometime in the evening it decided to stop feeding and just chew up the filament. Not sure what happened. It ran with nothing coming out, and the bolt has chewed a spot in the filament and it is not feeding. Just printed a 3" cube to about 2.5" tall with 4% fill. I will go in tonight, clean it out, make sure that there is no jam, and clean the bed again. Take the part and toss it into the Failed parts pile. Someday I will find a way to recycle that stuff. Any idea why it would do this in the middle of a print when it was doing just fine up till then?

I can take a couple pictures when I get home tonight.

There are a couple of possibilities:

* One way that this can happen is if there was a sudden thick spot in your filament. If the diameter of the filament varies too far, it can jam on the way into the hot end and simply get stuck while the hobbed bolt chews away. These variations show up more often in cheaper filament (less process control). I have noticed that it also happens more often later in the roll. One reason for this is that the filament can soak up water from the air and start to expand. It can also just be variability.
* If this continues to happen, I would look at your retraction distance. You can set both the minimum distance to extrude before another retraction as well as how far the filament retracts. If the same section of filament is pushed back and forth past the hobbed bolt, it can get chewed up and the hobbed bolt loses traction on the filment. Then, the bolt just spins and chews more and more of the filament away. This cause is more common with particular models as it relates to the frequency at which the filament is extruded and retracted.

Both of these area avoidable problems, but they happen to the best of us. To test for the water issue, listen as your filament is extruded. If is hisses and pops, then I would recommend drying your filament out (you can heat it in an oven at ~105C for an hour or so) and then store it in a small airtight box. I have a few lidded plastic boxes that I found at Target for this. The retraction issue is harder to nail down. The acceptable/necessary retraction depends on the filament that you are using. ABS may get chewed up more than PLA and one batch of ABS may get chewed up more than another. If the water isn't the cause, you can just try to increase your extrusion length between retractions and decrease your retraction distance. You can also post your current values up here so that we can see if they are at reasonable values.

Thank You. I do not think it is a moisture problem as the filament was fresh out of an air tight bag with dessicant. When I am not actually printing, I pull it off the printer, put it in a big back, and throw the dissicant bags in it. I will look at the filament with the micrometer in a few places and see what the variation is. This filament is from the start of a roll sort of. I had the roll come in, and it did not fit my holder so I took and ran it from one spool to another that did fit, and in doing so the end of the roll is what I started from, and the part I am in now was the beginning of the roll. It could just be cheap filament.

I will post a couple pictures, and also post up the code when I get home tonight or tomorrow night.

Thank you for your help.

I had my (new) i3v 10" start chewing up filament over the weekend, right after I rebuilt my extruder with new printed parts. Turned out to be the large gear rubbing on the X-carriage screws behind it and binding. I think what happened is that it would try to feed a little bit, the gear would rub against the screw, and get stuck. So it ended up trying to extrude the same region of the filament over and over and chewed it up a little more every time. I adjusted the clearance and no more feed issues. Seems to feed more evenly now, too.

For me it was a combo of getting just the right tension on the guidler, and changing retraction settings in Cura.
Retraction Speed= 10
Distance= 1
Min Travel= 1.5
Enable Combining
Min Extrusion before restracting= 0.4
Z Hop= 0

I would have this issue when the filament was coming off the spool, sometimes it would bind on the spool a little, just enough to cause the issue. If the extruder is struggling to pull the filament, the hobbled bolt can start chewing the filament. To mitigate this, every so often during a print, especially for long prints, I would rotate the spool in the feed direction several times to create a lot of filament slack on the spool to decrease the chance of binding and make it so the extruder wouldnt have to pull as hard on the filament.

In the meantime, I switched from a 3.0 mm hot end to a 1.75mm hot end. The thinner filament is a lot lighter and easier for the extruder to pull than thicker filament.

Quote:

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Originally Posted by RaySuave

In the meantime, I switched from a 3.0 mm hot end to a 1.75mm hot end. The thinner filament is a lot lighter and easier for the extruder to pull than thicker filament.

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Although.... Because the filament is thinner, it means the extruder has to pull that much more of it off the spool to accomplish the same thing.