First things first, this is a mix from popular Anet A8 Fan Duct Spaceship edition V3 made by paul0.
To make this work I printed 4 versions and measured…. and measured again, there is no room to add a decent fan duct on Anycubic 4Max, everything is in the way, the belt, X and Y rods, Y carriage and X carriage. I don’t want to use zip ties or weird looking constructions.
The separator right after the fan in the duct is needed otherwise the air will only go through front pipe.
I had to butcher a lot to use original fan duct mounting points and get it fit there, the OEM one was also leaking air just where the fan connects to the duct, in my model you can push the fan on the duct and then use the original bolt and nuts to mount the fan on the duct.
I had to modify the pipes on paul0’s model to center the blowers with the nozzle and get it little higher from the bed.
So my apologies if you see weird shapes or flaws, this all I can put out with Tinkercad.
When printing use supports with “Touching Build Plate option”, if your printer suffers from overhanging at the fan opening where fan get mounted, add your own supports in Cura. If you don’t know how to add your own supports, search for “Adding Manual Support in Cura” on Youtube.