Hot & Cold Pulls

[last updated: 2022-08-13]
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• Hot and Cold Pulls - Setup:
• (link to:) YouTube video
• If you have filament already loaded, remove it.
• Pre-heat nozzle to 250
  insert Nylon filament
      white or clear so you can see any debris it picks up
  push Nylon through manually
      that is, without driving it with extruder gears
  until it comes out the nozzle; 1/4" coming out is enough
• At this point, you have two options: a "hot pull" (quicker) or a true "cold pull" (perhaps better cleaning).
  • "Hot pull":
    • immediately pull the filament back out
    • cut off end with whatever dirt it brought with it, and repeat 5-20x
    • this method is much faster, because you don't have to wait for the nozzle to cool and heat up again.
  • "Cold Pull":
    • (continuing from above, after pushing nylon filament through manually)
      reduce nozzle temperature to 0
    • continue pushing as nozzle cools until you can't get any more through (130-140C for nylon)
    • as the soft/molten nylon cools and congeals back to solid inside the extruder,
      it will capture debris left from previous filaments
    • let nozzle cool to 60C or so. Spped up cooling by turning on the print fan:
      Settings -> Temperatures -> Fan Speed - 255
    • When cool to 60c, cycle power to easily turn off fans, then raise the temperature to 250 again,
      and pull as the temperature rises.
    • it will finally come loose about 95C
    • when it comes out, it will drag out debris with it that has been partially clogging extruder and nozzle
    • repeat; amount of debris dragged out will be less with each repeat; continue until clean

  • when done, it's recommended to do a Z-calibration

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• On MMU:
• Cold pulls are a bit more difficult on the MMU.
• Remove the multiplexer, preheat the nozzle, and feed filament manually into the PTFE tubing until it begins to extrude through the nozzle.
• Print the relevant gcode file. [not sure what this is...]
• Continue to apply downward pressure as the filament cools to ensure that the cooling filament retains the shape of the nozzle.
• When the printer beeps, pull the filament out.

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