Easily removable fan mount to facilitate bed leveling, z-height adjustment, and nozzle changes.
The collar is for retrofitting a duct, if desired.
Created in TinkerCad, this part requires 2 8mm x 3mm neodymium magnets, epoxy, 2 1 1/2 inch 6-32 machine screws, 6 #6 nuts, and a 40mm fan. Use the images for assembly instructions. Supports shouldn't be necessary.