Burned filament on nozzle

  • Hey all,

    So I pretty much print exclusively in TPU right now. I have a flexion extruder and I have an issue with burned filament sticking to the nozzle and then getting in my print and ruining it. I tightened down heater block and the nozzle as tightly as I could to eliminate ooze, but I still encounter this problem. I was wondering if I could take a bronze brush and use that to automatically clean the nozzle before every print, so I don't get these burned spots on them.


  • Clean the nozzle before the print starts by manually brushing it and try reducing extrusion/flow a bit. Any over extrusion results in filament boogers sticking to the nozzle and charring, and eventually getting stuck to the print. I print TPU at 240C and get clean results.

    I tried using a brush to clean the nozzle automatically- it doesn't work. You have to brush and drag it over a silicone blade to really get it clean. It's not as easy as it would seem.

    trying to clean a nozzle

  • Slice Engineering also do a plastic repellent paint for nozzles. I have no idea if it works - just sayin'...............


    EDIT. I've also bought, but not yet tried, this dry PTFE spray https://wd40.co.uk/specialist/anti-friction-dry-ptfe-lubricant/.

    as I said, not yet tried it so.......

  • @mrehorstdmd Do you think a longer brush would work better? I could definitely get a silicone wiper set up on it pretty easily. I was thinking of about a 4" long brush.

  • I can only speak for PETG sticking to the nozzle but the problem is identical to what you are seeing with TPU.
    I have an automatic wiper action set up but this only happens at the beginning and end of the print so any accumulation during the print can still cause issues. Also, automatic cleaning, while it helps, is not 100%. I still end up manually cleaning the nozzle here and there.
    I have not bothered looking into cleaning the nozzle with my wiping setup during the print because it really isn't anywhere close to 100% effective. I would estimate a 60% effective rate.
    The Slice Engineering paint sounds interesting ....
    Regarding a longer brush - chances are there isn't enough stiffness and the bristles will just pass over whatever is on the nozzle.
    If you do find something that works, it would be great if you reported back.

    Edit: Was thinking longer bristles but maybe you meant same height of bristles but bigger brushing area - I find that bristles by themselves are really not useful and a silicone wiper works much better. A larger brush would reduce the chances of the old crap being picked up on a new pass so yes, you will see some improvement.

  • Are you sure your nozzle is exactly perpendicular to the print? Makes quite a difference on my printer

  • So I'm going to try this and see how it works. Just picked up a brush at walmart and have a mount printing right now. Will let everybody know how it works.


  • @Surgikill

    how to do you like your flexion extruder? I had a double one , the only things left of it ,is the aluminum bar now , both barrel would jam , extruder would stop feeding , it was a nightmare .

  • @Dad003 It works. I don't think it is worth the money. I'm waiting to buy a hemera. It just seems like an all around better extruder for a cheaper price. The biggest gripes I have with the flexion are the heater block assembly and the fact that I have to use a massive motor on it. I also have to adjust the tension with that cam system to change filament which is a pain in the ass. The heater block assembly is something straight out of 2016. I've broken 2 thermistors and I couldn't get the heater block in initially. The little wheel that's supposed to clean the teeth of the feed gear has stopped working as well.

    I can fit a hemera on my toolhead with a fan that has the same footprint as a flexion without, and weighs less, plus I don't have to mess with shitty thermistors and a finicky tension adjuster.

  • @Surgikill

    yep look good in theory but work really bad , i replaced mine with bondtech bmg-X2 ,

  • Well, some prelim testing with the brush shows that it's okay, but not great by any stretch. Maybe if I modify the routine a little bit then it will work better. Maybe with something like the nozzle-x it would work well.

  • 0.35mm and 0.6mm Nozzle-X's are my daily driver and so far they are still going as strong as they did on day 1. Worth the money IMHO if your printing habits include abrasive filaments now and then or if you use a Chimera-style dual extrusion setup and want the nozzles to stay at the same height. I use brass only for the less frequently used sizes. But for filament sticking to the nozzle or easier release of debris they don't provide much of a benefit, at least not after several hours of use.

    Did you verify that your nozzle tip is strictly parallel to the build plate and not slightly tilted in some way?

  • @DaBit Last time I checked it was perfectly perpendicular. I think it just gets stuck to the nozzle during bed prove moves.

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