This is a Ender 3 Pro fan shroud compatible with 40x20mm cooling fans like the Sunon or Noctua offerings. This is a 100% stock replacement and utilizes the stock mounting screws as well as stock cooling fan and duct. I printed this out of PLA and have not had any problems with warping or melting so far.
with this design I did not want to have screws visible from the front side of the shroud. By doing so the 4 posts go inside the holes the can screws use. I would recommend using using as short of an M3 screw as possible to reduce the chance of breaking the posts when (do not over tighten). 1 screw and 2 posts is more than sufficient enough to hold the fan on.
I created this because I wanted to retain the factory look of the printer while utilizing a higher quality fan. I have included the F3d files as well as IGES and STEP files along side the STL.
This should be 100% compatible with the standard Ender 3.
March 2, 2019 Update
I reworked the model a bit. I changed the fan mounting so that a standard coarse thread fan mounting screw holds the fan on instead of dealing with the delicate posts. I also added a wing for mounting a BL Touch or any other bed leveling sensor. I have refined some of the openings and increased the thickness of a few mounting areas as well.
The BL Touch mount from https://www.thingiverse.com/thing:3148733 is compatible with this updated version of the shroud.
BL Touch Offsets
X offset is 47mm
Y offset is 13mm
Print with fan grill down. Support is optional but recommended for the 2 mounting tabs at the top.