Fan duct/Fan shroud
Fan duct or Fan shroud help the fan to cool printed objects. With better cooling, objects tend to have less warping and have more attractive finishing surfaces. There are may model out there. Some look more fancy than others. So which one should you print?
Desi Quintans has conduct an experiment with different type of fan shroud with the fan by printrbot and an upgrade version. Here is the conclusion.
Without any modification from the Printrbot Simple Metal’s fan, the best option is to print the fan that is recommended by pintrbot site. Or even better, try the modified version by the auther, here
I found this model is the best. You can print everything out from any 3d printer and there is no need for extra fasteners or glue.