I've heard that when the teflon starts to wear, the cold pulls will start to look something like this. How many hours do you have on the teflon insulator, and what material/temps are you printing?
Speaking from my own experience, when I put new teflon insulators on, it changes many characteristics of filament flow (for the better) such as cold pulls, retraction, and feeder tension)
I've heard that when the teflon starts to wear, the cold pulls will start to look something like this. How many hours do you have on the teflon insulator, and what material/temps are you printing?
Speaking from my own experience, when I put new teflon insulators on, it changes many characteristics of filament flow (for the better) such as cold pulls, retraction, and feeder tension)
Its a new machine. 150 hours of printing. All has been PLA at 220c except for 2 small woodfill fine prints (failed prints). I will have to see about getting some more teflon insulators. Just seems way too soon to have problems, I havent had the machine 2 weeks or so.
Maybe the woodfill print failed becasue you were printing too slow? You can't let woodfill stay in the nozzle long while in Tg (glass transition stage). Carbon buildup forms and clogs the nozzle. I suppose you could have some sort of build up somewhere in the nozzle, which would mimic a bad insulator. If you're the hands on type, you can always inspect the hot end and insulator if you're continuing to get bad prints.
When you heat the nozzle to 180C or hotter before doing the "atomic pull", also then push the filament into the feeder by hand - it will only move 5 to 10mm. Then let it cool to 90C and pull it out and it should look more "normal".
Either that or you aren't cooling enough. For me 95C to 100C is cool enough to get it out in one piece without this much stretching in your photo. But maybe you need to cool slightly more or let it sit at 95C for a full minute.
I have had my UM2 for a couple of weeks. It arrived with a blocked nozzle and I unblocked it with the Atomic method. I have made about 15 prints so far, each of several hours. Last night the nozzle blocked mid print. I had changed the settings from 50mm/sec to 80 to speed up a print with an stl of 80Mb! I restarted the print and it started and blacked after an hour. Now unblocked with the atomic method again. My filament also looks stretched as the OP's.
I am only printing with PLA.
Surely it should not block this frequently?
Check your Bowden tube for small black particles. If you find any of them they come most likely from the feeder case. It might help to replace the feeder with a printed one.
When you heat the nozzle to 180C or hotter before doing the "atomic pull", also then push the filament into the feeder by hand - it will only move 5 to 10mm. Then let it cool to 90C and pull it out and it should look more "normal".
I normally remove the bowden tube from the print head to do the atomic method. So I will heat to 230-260, insert the material, normally push some through the nozzle to make sure it is flowing good, then let cool to 80c-100c and let sit for a minute before pulling.
Check your Bowden tube for small black particles. If you find any of them they come most likely from the feeder case. It might help to replace the feeder with a printed one.
I also would like to replace the feeder. Its on my short list 
The temperatures for the atomic method depends on what material you're using for it.
I use mainly Colorfabb filaments and usually i pick the first light colour i find (light to see the impurities that are taken out). For me at 90°c i have the same result. i have to go down to 85°c or less depending on the colour.
If it's too low you won't be able to pull it without a lot of force, if too hot it will deform like you show. Usually when it happens to me i pull very lightly to have most (or all) of the filament out. It will still work if you have the tip of the filament in the shape of the inside of the nozzle.
It's probably less efficient because sometimes you leave parts in the nozzle...
I am having this same issue right now, though the hotend went from slightly blocked, the reason to attempt a pull, to completely blocked :( I tried pulling at a cooler 80 degrees, but I still get the stringy pulls.
I guess I will have to take the whole thing apart tomorrow. I have spares, though I would rather only use them if absolutely needed.
Well, today I poked a hole through the hotend with a fine needle a couple of times, freeing up the flow. Atomic pulls still come up weird. Lowered the temperature, retried, still weird. I threw up my hands, put the hotend back together and attempted a print only to find out that everything prints fine now. I have not tested a lot yet, about 1,5 or 2 hours worth of printing, but so far so good.
Not sure what to make of the weird pulls, but hey, if it works then I am not complaining. Added bonus is that bridging went from terrible to great
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smoke2000 0
that's actually how it looked when I tried the method as well.
I got my printer about a week now.
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