Scorpion hot end air duct causing heating failer and thermal runaway issues.

ishtobishtob Posts: 13Member
Just printed this duct 2 days ago and started to use it. Unfortunately a few seconds after getting to the layer where the cooling fan is set to turn on, the machine beeps and forces a restart with either "Heating fialure" or "Thermal runaway".

I know that marlin returns "Thermal runaway" for 2 reasons: catastrophic heating or if the heating element is at 100% for extended period and unable to reach target temp.

Looked back through the log in octoprint, looks like the cooling fan reduces the nozzle temperature by 15-20 degrees, and the heater was unable to get the temperature back up fast enough before that error kicked in.

Checking out the duct position, looks like the duct is pointing directly at the nozzle, could it be that the fan is cooling down the nozzle down faster than the heater can heat? any good way to solve this?

Post edited by ishtob on


  • eugenewithanaxeeugenewithanaxe Posts: 1Member
    edited January 22
    I had a similar issue with my fans cooling the nozzle/block. I resolved it by reducing the fan speed to 50%. 

    EDIT: I had a similar duct when I encountered the issues. I'm now using this duct:
    Post edited by eugenewithanaxe on
  • Stephen ToddStephen Todd Posts: 281🌟 Super Member 🌟
    On my A3s I have a 3 way duct very similar to the one in the original post

    In addition I have a front mounted fan and duct - so it total 4 direction cooling - and I have no problems at all

    My ducts point at the very tip of the nozzle in a downwards direction

    You could fit a silicone boot or whatever they are called over the hot end to get extra efficiency and keep any blown air off the hot end
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