30mm fan guard with anti-backwash

A fan guard (for the inlet side) with anti-backwash blades for 30mm fans. Helps prevent air spilling where it shouldn't.

The small size makes it a bit fiddly to print, but even quite rough prints seem to work very effectively. I printed it with 0.45mm width and 0.16mm layers. The holes take a #4-20 flat head thread rolling screw (or similar).

I use these for the fan on the extruder heat break with these fans

http://www.aliexpress.com/item/2-Pieces-Lot-12V-2p...