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.
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...?
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.
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!
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.
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...
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...
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.
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
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.
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
