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Backflow ABS

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Dear Ultimaker community,


I've had a problem related to backflow after printing with ABS in an S5; the part didn't stick to the bed, and before I could realise ABS had already gone up through the gap between the nozzle and the silicone covers. Fortunately, it seems that is has only reached the nozzle. I'd like to know, is there any guide on how to clean that plastic? How should I proceed without damaging any part?


Thank you



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    Posted · Backflow ABS

    Just heat the nozzle to about 120C in the menu on the printer.  Open the door and clean with a tissue or paper towel.


    More importantly - this is called a "head flood" and you got the most mild version ever but it can be a disaster.  It's never happened to me but it happens a lot - especially to people who have printed fewer than 100 prints.


    The fix is to get your parts to stick better to the bed.  Ultimaker has much advice on this.  I have a whole video on this on youtube.  The main tricks:  squish, temperature, brim, rounded corners, glue.  I talk about each of these for many minutes as they are complicated and it's good to understand.


    squish, temp, brim are set by the ABS profile by default.  Don't skip brim if your parts aren't sticking (I don't use brim except very rarely for the most difficult of prints).  So if you haven't messed with profiles you probably just need to worry about the last issue, glue.  I recommend Magigoo.  They have a product specifically for ABS.  Get that.  It will save you major headache (no head flood).


    If you have 20 minutes, this video will teach you a lot:


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    Posted · Backflow ABS

    Thank you both for your help! I tried first heating it up and it went off in one piece, so it wasn't necessary to use acetone; I imagine it can be helpful in more severe cases.


    Anyway, I realised that the Print Core 1, where it all happened, doesn't fit with the silicone cover so good as in the Print Core 2, as number 2 is a little bit lower than the first. That said, I imagine it's easier to have head flooding in the first one rather than in the second. So, do you know if there is any other option to protect better the first printcore? Like a tighter silicone nozzle cover?


    Thank you again,


    PS: kudos for your video gr5! Nice to see and very helpful!

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