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Stuck PLA filament

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Our school has the Ultimaker 2

I did the Atomic Bomb cleaning method whilst using white PLA. The filament is now stuck and will not retract. Any suggestions will be greatly appreciated. Thanks.


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Bob, not bomb. Atomic Bob.

So I'm not sure what you did. Are you simply saying 90C is not hot enough to pull it out? It's okay to try 95C or even 100C (95C should be fine - 90C is usually perfect). Here's the instructions for "atomic" method:


Or maybe you took the bowden off and now it's not working right? I'm just confused as to what the problem is that you are having. Or can you not take it out even at 180C? Sometimes you can get an upper print head clog. These usually occur when the 3rd fan isn't working.

Or maybe you are trying to do it and the feeder stepper is still on. Just turn the printer off to get the feeder stepper to be off and when you turn it back on avoid menu itmes that turn feeder on such as "change filament" (haven't used that in over a year now) or "move filament" or "home" or "print". I think those are the only ones that power up the feeder - instead stick with setting the nozzle temp menu item only.


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Thanks for the reply. i was trying to be cute with "Atomic Bomb". I use this term because it seems like the last report "nuclear option" for poor extrusion. I used a higher temp and removed the filament. I did the Atomic Bob clean a few more times but I still see uneven extrusion. I attached the following image to illustrate the resulting print Any suggestions are greatly appreciated.


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That picture you posted is on your computer still - I can't get to your computer (good thing!). Please click "gallery" on the top left of this page, then click big blue "upload" button, then do a new post (so I'll notice) and click "my media" next to smile face to insert your picture.


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Underextrusion has many causes. The most common is printing too cold or too fast. Even if you've printed at these temp/speeds before, raise the temp by 20C but don't exceed 240C and if you were already at 240C, lower the printing speed by 50%. Think of this as not a permanent solution but an experiment.


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As far as underextrusion causes - there's just so damn many. none of the issues seem to cause more than 20% of

problems so you need to know the top 5 issues to cover 75% of the possibilities and 1/4 people still won't have the

right issue. Some of the top issues:

1) Print slower and hotter! Here are top recommended speeds for .2mm layers (twice as fast for .1mm layers):

20mm/sec at 200C

30mm/sec at 210C

40mm/sec at 225C

50mm/sec at 240C

The printer can do double these speeds but with huge difficulty and usually with a loss in part quality due to underextrusion.

2) Isolator - this is most common if you've printed extra hot (>240C) for a few hours or regular temps (220C) for

100 hours. It warps. It's the white part touching the heater block. Test it by removing it and passing filament

though it by hand.

3) Curved filament at end of spool - if you are past half way on spool, try a fresh spool as a test.

4) curved angle feeding into feeder - put the filament on the floor -makes a MASSIVE difference.

5) Head too tight? Bizarrely MANY people loosen the 4 screws on the head by just a bit maybe 1/2 mm and suddenly

they can print just fine! Has to do with pressure on the white teflon isolator.

5b) Bowden pushing too hard - for the same reason you don't want the bowden pushing too hard on the isolator.

5c) Spring pushing too hard. Although you want a gap you want as small as possible a gap between teflon isolator and steel isolator nut such that the spring is compressed as little as possible.

6) clogged nozzle - the number one problem of course - even if it seems clear. There can be build up on the inside

of the nozzle that only burning with a flame can turn to ash and remove. Sometimes a grain of sand gets in there

but that's more obvious (it just won't print). Atomic method (cold pull) helps but occasionally you need to remove

the entire heater block/nozzle assembly and use flame.

7) feeder spring issues - too tight, too loose

8) Other feeder issues, one of the nuts holding machine together often interferes with the feeder motor tilting it

enough so that it still works but not very well. Other things that tilt the feeder motor, sleeve misaligned so it

doesn't get a good grip. Gunk clogging the mechanism in there.

9) Filament diameter too big - 3mm is too much. 3mm filament is usually 2.85mm nominal or sometimes 2.9mm +/- .05. But some manufacturers (especially in china) make true 3.0mm filament with a tolerance of .1mm which is useless in an Ultimaker. It will print for a few meters and then clog so tight in the bowden you will have to remove the bowden from both ends to get the filament out. Throw that filament in the trash! It will save you weeks of pain.



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