Duplicator D9 fan duct II

After switching to a bondtech extruder on my Duplicator D9 (400 MK2) I noticed an increase in heat-creep induced artifacts on my low-temp material prints. I was expecting this somehow since a few factors are handicapping proper hotend-cooling on this machine:

all-metal hotend
replacement of the aluminum extruder block by a plastic extruder block
printer in enclosure

So after I semi-failed on the part-cooling fan (https://www.thingiverse.com/thing:4044949), I decided to give up my previous approach in trying to use the given fan and started with shopping for the most ridiculously overpowered 24V radial fan I was able to get my hands on.

Here's that beast:
https://www.distrelec.at/de/radialluefter-dc-dc-51x15x51mm-24v-6m-rlf-35-ebmpapst-rlf35-14n/p/15421093

Finally I'm able to use my hotend as a hair dryer. But my actual goal was to never-again worry about heat-creep, and this one - although pretty pricey - does that job very well. A cheaper and more silent fan might be a better idea in most cases since this one draws more current than the printers mainboards can supply. A more sane fan-choice with a power rating that matches the original one will spare you tapping 24V directly from the PSU. Further downsides are an increased noise level (which isn't an issue since it's under a cover) and more weight (very close to the x-axis, so no big deal either).

To prevent the duct from leaking and causing drafts over your print I recommend lining the x-carriage with some sponge rubber. And this is the only thing you need except from the fan and the duct. Oh: and some tape or foil to cover that big hole right underneath the original fan. You can see it in one of my pictures as some yellow foil. The fan is mounted by clipping it into the duct and the duct is held in place by 2 screws that are already installed on the stock hotend. Just use these and maybe some shims.

That's it. Good luck.

Further plans: A slider to split the airflow and use it for extruder motor cooling or part cooling would be nice. And maybe make an adapter for the fan to suck air from outside the print chamber.