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Unresolved Nozzle temperature fluctuating wildly (PID autotune related)

Discussion in 'Troubleshooting' started by Malek, May 24, 2017.

  1. Malek

    Malek Member

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    I don't think I have a problem with my heater or thermistor, and for a long time my temperature was behaving, but on my last print it kept fluctuating like crazy between 190 and 215 (I had it set to 210). This started happening right after I ran the PID autotune routine for the nozzle. However, I ran it with both my fans running on full blast at 255 and my nozzle as close to the bed as possible (to simulate airflow hitting nozzle as it's printing). However, when the printer is printing and the fans are off (or not on full blast), that's when the temperature fluctuates severely. So my question is, how exactly are we supposed to run through the PID autotune routine when printing conditions are constantly changing? My first 1-2 layers the fans are off, then they come on, and even if I have them at 30%, they lower the temperature drastically and trigger a temp runaway error. What are the pros here doing to prevent this? Here are some things that I'm planning on doing:

    1. Installing some sort of cotton (or similar) hot end insulation to prevent air from affecting it.
    2. Upgrading the heater to 40W. I think I have the 30W (already ordered this).
    3. Finding better fan shrouds. Any recommendations?
     
    #1 Malek, May 24, 2017
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    >1. Installing some sort of cotton (or similar) hot end insulation to prevent air from affecting it.
    Not likely to help. Nothing short of asbestos at least :)

    >2. Upgrading the heater to 40W. I think I have the 30W (already ordered this).
    THIS. THIS IS your best bet.

    >3. Finding better fan shrouds. Any recommendations?
    Make sure the shroud you use is specific to the extruder you have. If you have (for examples) a hexagon then make sure you have a hexagon shroud, not an E3D. If you have an E3D v6 make sure you download and print a v6 shroud, not a v5. That is the sort of thing you need. Quite honestly I run one with no shroud at all. The stock cooling fans are really poor at moving air.
     
    #2 mark tomlinson, May 24, 2017
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  3. Malek

    Malek Member

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    Thank for that! I am hopeful that the 40W will help, although I have to say, I have no idea what wattage is on there right now. I bought a used printer and don't know what the old owner has done with it.

    But I still don't know, should I be running the PID autotune with the fans off? Or is it a good idea to have *some* airflow? I've done a lot of reading all over the net on the subject and people have various opinions. Clearly having them at full blast is a no-no.

    I also see that there are people who have wrapped their heat blocks with special insulation material (not kapton) that they sell specifically for this purpose and have said that it made a huge difference... They're cheap so I might try it anyways and see if it makes a difference.
     
    #3 Malek, May 25, 2017
  4. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    Also the PID tuning is not perfect, I would suggest that you PID tune then use M301 to set the variables then PID tune a second time, repeat for one more iteration and the final numbers should be perfect.
    Code:
    M303 S<temperature> C<cycles>
M301 H1 P<results from above>  I<results from above> D<results from above>
M303 S<temperature> C<cycles>
M301 H1 P<results from above>  I<results from above> D<results from above>
M303 S<temperature> C<cycles>
M301 H1 P<results from above>  I<results from above> D<results from above>
     
    #4 WheresWaldo, May 25, 2017
  5. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    There is the blue 'sock' available for the E3D that is supposed to help it with this, but then again, the E3D comes with a 25w heater (No idea why they do that - I switched mine to the 40w).

    http://e3d-online.com/V6-Sock-Kit-3-Pack
     
    #5 mark tomlinson, May 25, 2017
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  6. Geof

    Geof Volunteer Moderator
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    30 Watt heater now. The sock is...problematic for me so I pull them off. My Prusa has a fluctuation problem that is related to a sloppy connection in the wiring. If your using a quick connect grab that sucker and wiggle the crap out of it, if the temp goes up and down and all over you have found your issue :D
     
    #6 Geof, May 25, 2017
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