Weird stringing/overhang issue not present before.



  • So I just swapped my nozzle out for a .4mm hardened steel nozzle. This was printed at 0.2mm layer height, TPU filament, 240C.

    The left print was the first print out of the nozzle. Came out okay, but had some underextrusion due to jams. Middle print is the second print at the same temperature. I have no idea why there are a bunch of strings in it. It looks like the plastic wasn't adhering to the layer beneath it and it was just being pulled around the edge of the piece.

    Right piece the temp was bumped up 15C to 255C.

    No clue what to make of it.

    https://i.imgur.com/bFLlKKM.jpg



  • @surgikill said in Weird stringing/overhang issue not present before.:

    hardened steel nozzle

    It's common to need to increase your printing temperature with hardened steel nozzles due to the lower thermal conductivity.

    Did anything else get nudged when you installed it? Cooling duct maybe blowing more on the heater block?

    You could try re-running the PID tune.



  • @phaedrux There's no print cooling fan installed yet. As you can see, the left print and the middle print were both printed at the same temperature, one right after the other. The right most print did have the temp bumped up by 15C. Are you telling me I have to go higher than that? The most I've seen online is 5-10C.



  • No, 15c sounds about right.

    Try and think of anything else that may have changed.
    Try different filament?
    If you swap back to the old nozzle is it better?



  • @phaedrux said in Weird stringing/overhang issue not present before.:

    No, 15c sounds about right.

    Try and think of anything else that may have changed.
    Try different filament?
    If you swap back to the old nozzle is it better?

    I can try switching back to the old nozzle, but it puzzles me that I got an almost perfect print with the steel nozzle on my first print, then my second print with the steel nozzle I got a terrible print. Same print settings and everything. It was the exact same file. I'm trying another print with the steel nozzle right now to see if it works or not.



  • Partial clog?
    Did you hot tighten the new nozzle? Perhaps there's a bit of a leak?



  • @phaedrux said in Weird stringing/overhang issue not present before.:

    Partial clog?
    Did you hot tighten the new nozzle? Perhaps there's a bit of a leak?

    Tightened the new nozzle at 220C with a socket. Maybe it's clogged, but it's not printing like it is.



  • @phaedrux Well, I just printed 2 more. The first one came out damn near perfect, and the second one has the stringing present. Maybe my filament diameter is off?



  • TPU is tough to print at the best of times, and circles like that are also tough because the filament gets dragged along the inner surface and if it doesn't adhere, it can get pulled out just like in the photos.

    Things I might try:
    Increasing temperature beyond what you already have
    Slow down the print
    Increase the extrusion factor



  • @phaedrux said in Weird stringing/overhang issue not present before.:

    TPU is tough to print at the best of times, and circles like that are also tough because the filament gets dragged along the inner surface and if it doesn't adhere, it can get pulled out just like in the photos.

    Things I might try:
    Increasing temperature beyond what you already have
    Slow down the print
    Increase the extrusion factor

    I'll try those. Maybe part cooling would help. I need to get that hooked up.


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