heater block temperature gradient

Discussion in 'BigBox General Chat' started by R Design, Jan 16, 2017.

  1. R Design

    R Design Well-Known Member

    Joined:
    Oct 7, 2015
    Messages:
    918
    Likes Received:
    183
    This weekend the Sock on my hotend died (became floppy and fell off). Since the nozzle needed cleaning I didn't replace it right away but carried on printing.

    This Monday morning notice all parts printed showed more signs of ooze than usual + there was some stringing.

    Hypothesis: without protection from the Sock, the fan (kickstarter original!) cools the left side of the heater block which is where the thermocouple is mounted. Marlin makes the heater cartridge work to maintain temperature. Net result is a left/right temperature gradient across the hotend and much of the filament experiences a temperature greater than that on the dial. Hence oozing.

    What do you think?
     
  2. Falc.be

    Falc.be Well-Known Member

    Joined:
    Sep 4, 2015
    Messages:
    243
    Likes Received:
    38
    thats the exact reason why the sock was created
     
  3. R Design

    R Design Well-Known Member

    Joined:
    Oct 7, 2015
    Messages:
    918
    Likes Received:
    183
    ;)

    thermal stability would definitely be a part of it's reason for being...

    but it's new to me the idea that when the hot end is being cooled by the parts fan the nozzle might actually end up too hot!
     
  4. elmoret

    elmoret Administrator

    Joined:
    Mar 1, 2014
    Messages:
    586
    Likes Received:
    91
    The heater block shouldn't be subjected to airflow from a part cooling fan, if it is the duct needs adjusted/redesigned.

    I modeled it once, assuming there isn't a fan blowing on the heater block the temperature gradient was less than 2degC throughout the block at printing temperatures. I included the ~7w of heat flow into the nozzle, as that's average for melting an average polymer at average flow rates. Then 5-7w goes up the heatbreak, and about 5w lost to ambient.
     

Share This Page