Hemera Heatsink Cooling

Discussion in 'HotEnds & Extruders' started by Thorinair, Jan 10, 2020.

  1. Hermes Hermera

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    It just never made sense to me, to have that type of fan blow onto a that heat sink design. I reversed it as soon as I found some longer screws.

    Blowing air over a surface of that makes a sudden 90 degree turn causes a lot of turbulence, a better laminar flow can be achieved if the air is pulled over a surface. Plus that type of fan doesn't provide the static pressure required to make that turn. Not a fluid dynamics engineer, but I have worked with a few and seen a one or two flow test performed.
    Then again I never performed an actual temp survey so I could be completely wrong, fluid dynamics can be a tricky thing.

    Someday I'll put a temp probe on it and compare it with a lower flow Noctua and see if there is a notable temp increase. My guess is at temps =/< 210c it will be negligible.

    Oh, and there's the added benefit of not getting air blowing in my face.
     
  2. Thorinair

    Thorinair Well-Known Member

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    The way how Hemera is designed with its heatsink actually captures the turbulent flows and stabilizes them. The flow comes out of the fan in a spiraly way, and this starts flowing along the spiraly design of the heatsink. It is designed like this for a reason. Also, it is meant to blow like that, so it doesn't blow air all over your print and cause warping. Just maybe don't have your face in front of it...?
     
  3. Spoon Unit

    Spoon Unit Well-Known Member

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    Not really sure where to put this, so this will have to do. I ran into a nasty jam during retraction with the Hemera, when trying to eject and change filament and it was the result of possibly a combination of things:

    Strength of Hemera
    Retracting too fast
    Using Bowden tube (as it was easy to hand) instead of a higher ID feeder tube, thus increasing the force required to push the filament out.

    From what I can gather, the following happened.

    Ejection starts
    Happens way too fast
    Hot plastic gets crushed between the hobs
    Plastic deforms and will no longer exit
    Plastic is pushed sideway and quickly cools in such a way you'll never get it out without dismantling.

    My ejection strategy is now encoded into a macro I can call. I'll probably tweak this further, but right now it's pretty fast and works well.

    G1 E28 F800 ; Push
    G1 E-28 F5000 ; extract filament into heatbreak
    G4 S5 ; allow filament to cool
    G1 E-30 F800 ; eject

    Hopefully it can help save someone else from some severe frustration.
     
  4. Thorinair

    Thorinair Well-Known Member

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    I actually had exactly the same problem. My tactic is to hold onto the filament when ejecting and pulling on it as soon as it clears the gears. This helps prevent such a clog. I do like your idea though!
     
  5. Spoon Unit

    Spoon Unit Well-Known Member

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    I was surprised at just how clean the end is using this method. No way it's going to jam or deform in the same way once it's cold.
     
  6. SchmartMaker

    SchmartMaker Active Member

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    I'm took some cues from the skinnydip approach to shape the tip before unloading PETG and I unload the filament at a lower temperature than the regular printing temperature. I have not found the ideal setting yet however. I'll try your macro to see how this pans out for PETG...
     
  7. Spoon Unit

    Spoon Unit Well-Known Member

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    Feedback would be great.

    Another thing I've done is to cut the feeder tube about 2cm above the collet. This way, there's less friction to push against during eject. I really need to order the right tubing too...
     
  8. SchmartMaker

    SchmartMaker Active Member

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    I've just tried your macro, and I'm getting a fairly stringy tip with PETG. For comparison, I've included a picture showing the results of my own (still imperfect) skinnydip-inspired macro. The first tip is the result of my code, the bottom tip is the result of yours. I'll include my macro in a separate post shortly.

    ED9C5F34-37D0-4D5D-9E93-4B1159DBCAA5.jpeg
     
  9. SchmartMaker

    SchmartMaker Active Member

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    This is the unload macro that I'm still working on. Note that I use a much lower temperature (at 200C) than my regular printing temperature of 240C and even let it cool off further during the unload procedure. Therefore, I'm using very slow extrudes and retracts.

    Code:
    G21            ; Use millimeter units
    M83            ; Set extruder to relative mode
    M109 S200      ; Wait for hotend to reach target temperature
    M104 S0        ; Disable hotend immediately
    G1 E20 F120    ; Extrude 20mm with a speed of 2mm/s
    
    G1 E-2 F600    ; Retract 2mm with a speed of 10mm/s
    G4 P1000       ; Wait for 1s
    
    G1 E-5 F60     ; Retract 5mm more with a speed of 1mm/s
    
    G1 E4.8 F60    ; Dip tip back in slowly
    G1 E-5 F60     ; Pull it out again
    G1 E4.8 F60    ; Dip tip back in slowly
    G1 E-5 F60     ; Pull it out again
    G1 E4.8 F60    ; Dip tip back in slowly
    G1 E-5 F60     ; Pull it out again
    
    G1 E-50 F3600  ; Retract 50mm with a speed of 60mm/s
    
     
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  10. Spoon Unit

    Spoon Unit Well-Known Member

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    I may try a cold pull macro too, as that then carries the benefit of removing most of the previous material from the nozzle, particularly useful if you're changing materials.
     
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  11. Spoon Unit

    Spoon Unit Well-Known Member

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    Here's a cold extrude macro to play with:

    Code:
    M104 T3 S120    ; Warm Tool To 120
    T3                ; Select Tool
    M302 P1    S110    ; Enable Cold Extrusion at 110
    G1 E-28 F800    ; extract filament into heatbreak
    G4 S1            ; allow filament to cool
    G1 E-30 F3600    ; eject
    M302 P0            ; Disable Cold Extrusion
    T-1                ; Drop Tool
     
  12. BennoDXB

    BennoDXB Member

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    Heya, did you link the right fan? Thats a 12v fan or are you using a buck converter?
     
  13. Thorinair

    Thorinair Well-Known Member

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    What makes you think that I use 24V?
     

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