Anycubic i3 Mega (S) Mainboard/Stepper Fan Duct - 50mm and 40mm

thingiverse

Remixed this fan duct to work with the stock 50mm fan, using M3 screws with slots for nuts to attach the fan easily. Then I made a version with the original hole size for the Noctua rubber mounting things, as well as 40mm versions of both. I also took out the cutout on the shroud, moved the air hole on the end piece and extended the mounting bracket on the end piece so that it could be pressed right up against the side of the case. I found the easiest way to install it is to slide the long part of the duct under the needed wires sideways, and then rotate it into place. With the duct pushed up against the power supply, you can rotate the end piece into place and then slide the duct until the mounting hole matches up. You can always remove the power supply if you're having trouble.