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Stringing

Discussion in 'Filament' started by Lance Weston, Jul 7, 2020.

  1. Lance Weston

    Lance Weston Active Member

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    I was having a stringing problem.

    All of my filament is fed directly from a dehydrator and is kept at less than 10% RH. With COVID I could not get SUNLU PLA not PLA+ my preferred filament due to the rise in price. I got Esun and Hatchbox. I am printing a production part, so it is the same part in the same place over and over.

    Starting with Esun I got stringing at 215C I worked my way down to 185C and it was still there. I kept increasing my retraction until 6mm, still there. I flipped to Hatchbox and got the same results. I found a roll of SUNLU thinking it would solve my problem, but the same thing happened. I did this over the course of 45 pieces.

    I then stepped the hotend up to 225C positing that the retraction would work better hotter. It did, and stringing is gone. This runs counter to all that I have read on reducing stringing. I am printing out of the temp range of the filament.

    I am looking for insight and others real world experience.
     
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  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I have used some Nylons that do that -- string when too cold rather than too hot.
    In general though (for PLA/ABS) the stringing is pointing to too much heat rather than too little.

    Ultimately the temperature range they quote when you look at filament is not a rule, it is a guideline ;) Whatever works is the rule.
     
  3. Lance Weston

    Lance Weston Active Member

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    I am thinking it has something to do with minimum temperature for retraction. I am now going work the variables to find the golden retraction/temp. At four parts per day it wil take awhile for me to get back with results.
     
  4. Lance Weston

    Lance Weston Active Member

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    I found the why two of my machines string and one does not. Below is a picture of my shroud and the Robo shroud. My shroud pushes air much closer to the nozzle, it also shields the heater block from the airflow and contains the airflow over the print, this results in a much higher airflow on the print. I had swapped everything but the fans. I use double ball bearing high output fans. The machine with no stringing did not have the original fans swapped out and the fans in it are much lower output. After I put in the double ball bearing fans I got stringing. I reduced the fan speed from 30% to 10% and all of my machines no longer string.

    I guess there is a point where more airflow is no good....
     

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  5. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Agreed. The parts cooling pan should only be putting air on the part printing.
    If it splashes up on the hotend it will cause more problems. Not only that but it needs to be enough airflow to cool the part fast enough. The stock fans on the R1 series were abysmal and you really needed to :
    1) Duct them
    2) use better fans
     
  6. tkoco

    tkoco - -.- --- -.-. ---
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    Very interesting.
     

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