irregular flow and cooling hexa fins

Hi,

Can anyone relate to irregular extrusion flow being a consequence of poor cooling of the Hexagon heatsink?

I manage to get some respectable prints with various material, but seems that after travel, or layer restart that first drop doesn’t come out properly or it comes too much.

I would like to think that it’s because of heat traveling a bit up the filament, therefore getting some irregular pressure.
But no way… this would be too easy to solve then :smiley:
It must be some kind of different sorcery. Something involving another 40 threads to be read :mrgreen:

Anyway, I made some custom cooling for fins, but seem to be getting a lot of back pressure from the fan. So it must be cooling the fins poorly… maybe due to my fan duct having sharp angles.

Would appreciate some thoughts on this

cheers

Do you habe a picture of your fan duct? Do you tried also this one? http://www.thingiverse.com/thing:845113
This fan ducts are not highly efficient from an aerodynamic point of few, but I will do some research and comparison to the original fan as soon as my TAZ 5 arrives…

Hi it’s somewhat similar.
Here is a video where you can see it. It’s only perpendicular rather then circular
https://www.youtube.com/watch?v=txij36kcCww

In your video, the print head is a single shiny white plane, I can’t see anything :wink:
But if it’s rectangular, that might make the air flow even worse. As a rule of thumb, you can say every change in flow cross section area is drag. If you reduce the flow area fast, it’s even worse with back flow in worst cases. Axial fans don’t like back pressure, thats why there is a radial fan in the stock design.

Maybe a fan duct for the original blower would be the best solution :exclamation:

So irregular flow can be a consequence of heat transfer to upper parts?
It wouldn’t just stop and it can happen that it gives some flow?