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Need Help with stringing

Discussion in 'Troubleshooting' started by Lance Weston, Aug 23, 2020.

  1. Lance Weston

    Lance Weston Active Member

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    I have three R2 machines in a basement with no air conditioning. The filament is fed to all three machines from dehydrators which keep the filament at 10% RH. All three have identical hotends with identical fans with identical firmware and gcode. The temp in the basement varies from 70F to 90F depending on outside temp and takes weeks to gradually change. The RH is upwards of 60% even with a dehumidifier.

    Even with 10% RH feed, in very rainy weather I get stringing in all machines. Now as we gradually change to fall and my basement humidity drops to 40% RH and 75F to 80F temperatures ( not changing the filament feed RH of 10% ) one of my machines is printing without stringing. The other two machines with identical lot and brand filament are stringing with the identical gcode.

    Has anyone else come across this and figured out how to make it work.
     
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Short of an enclosure? :)
    The knobs I tweak for stringing are usually retraction and (fine tuning) temperature*.

    Our dehumidifier does a good job of keeping the workshop at or below 40% which at least keeps it consistent.
    It is a bit odd that you are only seeing it on one, perhaps the thermistor is off a bit and your temperature is not exactly where you think it is.



    *but only for ABS/PLA, for nylon, PC and some others temperature is not really going to sort it.
     
  3. Lance Weston

    Lance Weston Active Member

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    Seems reasonable but, I had swapped the hotends and got the same results. When the machines are not running the LCD temps all agree to 0.5C so I ruled out the electronics. I had matched all of the 4.7K pullups on the thermistors. I live in Long Island New York. This time of year the humidity is just so high that nothing will keep up. I still have not figured out why room RH is important when the filament is maintained and fed from 10% RH box, but it is.
     
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  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    It is a bit hard to nail down -- the physics is not simple :)

    It seems odd that the room humidity would play a big role in there given that the filament is dry and has a short exposure to the room environment when printing, but it absolutely does. We ended up with 90% of the printers in the shop and the humidity controlled. I am in Florida -- humidity is our world, but I am not near the water and our workshop is smaller than trying to control RH in the house. I have a few smaller ones in the house, but at least one of those is a resin printer and those don't even react the same with humidity.
     
  5. Lance Weston

    Lance Weston Active Member

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    Thanks, I will install an air conditioner. This may also be related to room temperature. Room temperature also plays a part in the bed height. My bed height must be within +/- 0.02 when working with glass. Bed too high and the glass surface gets ripped off, too low and not enough adhesion. As the room temperature changes I have to track by modifying bed height in the eeprom. I move 0.01 at a time after examining the result of each print with temp changes. My aluminum extrusion machine which thinks it is an R2 does not have this problem.
     
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  6. Lance Weston

    Lance Weston Active Member

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    The machine that has no stringing is 3ft from the dehumidifier and the RH is 40% the machines that are stringing are about 15ft from the dehumidifier and the RH is 50%. I find no difference in temperature which is 79F.

    This confirms your conclusion that room RH matters even if the filament RH is very low. I now have a measurement I can make before wasting filament. This all begs the question of why. Does a 40% to 50% RH correspond to anyone elses observations of pass/fail.

    working with filament is like peeling an onion.
     
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  7. tkoco

    tkoco - -.- --- -.-. ---
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  8. Lance Weston

    Lance Weston Active Member

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    this is the exact product I use. One in every dehydrator box and one at every machine.
     
  9. Lance Weston

    Lance Weston Active Member

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    I still do not know what the difference is, but am working on it, but it is NOT room RH. My basement went up to 60%RH and the machine with no stringing continued with no stringing. The RH of of the filament is still maintained at 10%. I tried upping retraction from 1 to 6 on the stringing machines to no avail.
     
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  10. tkoco

    tkoco - -.- --- -.-. ---
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    What about retraction speed? Perhaps bumping that up a bit....
     
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  11. Lance Weston

    Lance Weston Active Member

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    You may be right. Installed air-conditioner today but it will take awhile to remove the heat and cool down the room and remove the humidity..
    I was using Esun and decided to throw in a roll of ANET I got cheap as a sanity check. First I ran the exact same GCODE and got the same stringing. I downloaded a cura profile for ANET and printed. The finish was not great, but there was no stringing. The big difference I saw was that the retraction went from the 1 I was using to 6.5. Now comes the task of resolving the two different profiles to get good finish and no stringing. If accomplished I will throw in anther roll of Esun and see if it tracks.

    I just might be on the edge with a retraction of 1.
     
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  12. Lance Weston

    Lance Weston Active Member

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    I have eliminated retraction, room temperature and humidity, spring pressure on filament, hotend ( swapped out working and stringing machine hotends with stringing following machine). I have today noticed that the dehydrator of the working machine is at 30% and the stringing machine at 10%. I will have to wait for 4 days for the filament to stabilize at 30% in the stringing machine.

    Is there an ideal RH for filament? Can it be too low? In four days I will see if it is the problem.
     
  13. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    The general rule of thumb has been "the dryer the better" but I am not aware of analysis regarding too dry :)
    It is possible.
     
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  14. tkoco

    tkoco - -.- --- -.-. ---
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    Mixed bag, depends on the chemistry of the filament. What is true for nylon filament has no bearing on other filament chemistry.
     
  15. Lance Weston

    Lance Weston Active Member

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    I have eliminated RH in the filament. On the machine with no stringing I gradually raised then lowered the RH. It seems that somewhere between 30% and 40% is the edge. Everything I printed below 30% RH was the same (down to 10% RH), perfect prints. When I went above 40% RH I got some slight nubbing and stringing. I am beating my head against a wall trying to figure out why two identical machines have different outputs (one stringing, one not). I am pretty sure when I do find it, I will go...that's obvious.
     

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