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Lopsided extrusion out of nozzle

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Both my printers have this problem now. On the UM2E+ sometimes the filament curls around to the right so much it sticks back to the nozzle, making a loop. Then the plastic stuck to the nozzle can end up dragging other lines around on the first layer. I also see it when pushing the plastic through the heated nozzle by hand during the atomic method: the extruded filament likes to curl in one direction. (This is sometimes associated with worse print quality and a bit of underextrusion)

Is this a common thing, and is it related to the PTFE coupler - or the nozzle? I tried the atomic method of cleaning on the UM2E+ and got a black ring around the plastic 12mm from the tip when I cold-pulled it out.

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It's usually not serious. You have lots of options:

1) Print a skirt far from the part so the blob doesn't get near the part.

2) Be ready and grab the filament after it is done priming. I just use my fingers and pull it away as the nozzle moves towards the start of the print.

3) Fix it.

If you do "move material" and grab the tip and pull it down a little and after 2 inches of "weight" of filament you let go and then move some more through the nozzle and it *still* does this curling then you have "curling level 2". If it isn't as bad as level 2 but will curl and hit the nozzle only when there is no filament pulling down then I call it "curling level 1".

Usually I don't fix "level 1" as it's pretty minor. I always fix "level 2".

it's caused by dirt or gunk at the very last mm in the .4mm wide pasageway near the tip of the nozzle. Think of this is a short tunnel going into the nozzle that quickly widens into a larger cave. The tunnel is the problem area.

Usually I can fix it by taking one of my nozzle cleaners (free with everyone's first order at my store) and rub it around in a circle a few times in the nozzle tip and then making sure it is fixed by doing move material. All this is done at temperature (e.g. 210C) and takes all of 30 seconds at the most.

If that doesn't do it you can either throw the nozzle away or try some more "cold pulls" (a proper cold pull includes pulling out a perfect inverted "tunnel" at the very tip and is hard to get without playing with the "cold" temperature). Or you can burn the nozzle gunk to a char followed by one more cold pull to get out the ash.

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Could you check if the hotend tilts a bit if you try to push the nozzle to the sides? (Cold ofc). If so your hotend might have a gap between the coupler/heater. A small little tiny gap where residue stays/burns/changes extrusion pressure. If not, just atomic it until that black ring disappears.

If it tilts, then you might need to screw the steel coupler a bit more (unless it's already touching the hotend)

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My hot end feels quite secure.

I'm trying again, main problems with curling are on the first layer where it's putting down "strings".  Some of the stuff sticks to the nozzle and of course when it's on there it's hot so it's sticky and starts sticking to other nearby filament and ends up destroying everything.

This time I paused during the first layer when I saw lots of plastic on the nozzle to clean it off.  Fingers crossed.

I'm doing a challenging print with 60 small components tiled across the whole bed area, printing all at once.  I've actually managed this 7 times before with a 48 component tiling that was almost as big.

[edit] Actually... The problem is in this first step that seems pointless: I told Cura I didn't want a brim, but it still draws a circle around each component. It's actually laying down these circles that causes the problem! Once the inner parts are filled, they stick better. I'll see if I can get a picture.WP_20160610_002.thumb.jpg.ba85f4934e222abde15ad9f280ce8afc.jpg


Edited by Guest

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After seeing the photo I'm assuming you only have "level 1" curling which is kind of normal.

It looks like you are doing "production". You might want to add custom gcodes between each print. There's no need for the skirt also - maybe getting rid of skirt will help? Set skirt lines to zero.

For "production" printing I've had to mess with gcodes betwen prints. I experimented with different things until I got it to work consistently. You certainly don't want the nozzle priming between prints! You don't want any pauses - you might want to get that nozzle back onto the glass quickly and away from the print.

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I found the skirt lines=0 option in Cura just now, re-levelled the build plate to be a bit closer to improve adhesion (hopefully the glassier base means no individual ones popping off) and it's going OK so far :)

I'm printing these "all at once" layer by layer rather than one at a time.

I may also try using the glue rather than just cleaning the build plate. Never had to use glue so far, but perhaps with this many small objects, guaranteeing adhesion would be good.

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