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Little drops, created at long prints

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Posted · Little drops, created at long prints

Hi, when I print a long print (17 hours+) with the Ultimaker 2+ connect (got it 2 weeks ago) the PLA forms little balls/drops like in the pictures that jams the printer. 


Anayone familiair with this and knows what to do to prevent it?


Thnx in advance 





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    Posted · Little drops, created at long prints

    In my experience there are several sorts of blobs:


    - Thick light brown blobs come from the outside of the printer: they accumulate on the outside, especially is there is a bit of overextrusion, and then they sag down and get deposited on the print, in a big blob, usually light brown. Upon the next passes of the nozzle, this blob is smeared out a bit.


    - Tiny, thin black flakes come from the inside of the nozzle: this is PLA that has been carbonised inside the nozzle, against the walls, or in-between the nozzle and teflon coupler, and then comes free and is washed away via the nozzle. Most often after a cold start.


    - Undiscoloured blobs (=not brown or black due to decomposition) can have lots of causes, for example due to layer-changes, the nozzle taking off or landing on a spot, very complex curves with a zillion facets where the printer buffer can not follow the data, nozzle oozing while traveling through air, etc.


    But I have never seen any such drops jamming a print or printer.


    Could you check and doublecheck if your temperatures are okay? If the nozzle would be way too hot (e.g. 250°C for PLA instead of 190-210°C), or the material flow way too low, I could imagine that the PLA would start to burn and carbonise completely in the nozzle? Then the coal might block the nozzle. Because the blob looks like burnt foam and coal on your photo, sort of?


    When I once tried burning PLA in a bunsenburner in a spoon, it almost completely vanished. So it burned very clean, leaving only a thin layer of black powder dust, that I could wipe off easily. But that might be different with other brands of PLA. On the other hand, PET left a thick, glossy and hard varnish, difficult hard to remove. During combustion, both had a phase where there was bubbling black liquid, foaming a bit, similar to what is on your photo.


    Also, be sure to clean off the nozzle after each print, so there are no remains. I do this immediately after a print finishes: I wipe it with a piece of thick paper towel, or leather cleaning cloth ("zeemvel" in Dutch), impregnated with PTFE oil, as this oil seems to reduce accumulation a little bit.


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