Wanhao duplicator i3 extruder assembly reference
thingiverse
Here are a few quick and dirty Solidworks models for the lower extruder assembly. This should be sufficient to enable you to create your own fan shroud around the existing geometry. This is currently a work in progress, and may differ to your extruder assembly slightly due to location of the heat block and it's orientation. but you should be able to adjust that in the assembly file to suit. Please point out any changes i can make. And feel free to improve upon these models by adding further detailing where required.
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