XL Fan Shroud 360°

I came to the conclusion from user feedback and even Prusa that my previous duct had some room for improvement.  Inspired by the MK4S duct, I went through many iterations of the duct to distribute air evenly around the nozzle but to the naked eye, improvements were hard to spot. 

I could only discern cooling improvements under a microscope.   

Given the available airflow, my goal was to evenly distribute air around the nozzle.  The best metric I could find to verify iterations was the pin support challenge found here.  The radial airflow improvement is quite significant.

My old design and the stock Prusa ducts yield the lopsided dome on the right.  After many iterations, this latest duct yields a pretty symmetric print, output in orange. 

Here's a comparison from the side.

It's fairly easy to print.  It requires a 0.4mm nozzle set to 0.2mm layer height (structural) to print well.  I strongly suggest to use supports and seam control as setup in the 3MF file.
Orientation on the bed is also important as the slicer makes assumptions on where to put the seams.  Ensure that the duct is sliced with two perimeters as shown below.

I printed mine in PC-CF on an MK4.  The supports come right off.

I encourage you to print any of your prefered stress tests to validate any improvement gains over the stock duct.  The effect of the concentrated directional flow of the stock duct is evident in the warping of the gray print above.  Keep in mind that this may be a benefit to specific geometry you may be printing.