CR-7: 40mm fan duct to nozzle (ring type)

Printer CR-7 has no nozzle fan. I design this fan duct for setup the second fan to cold down target quicker.

Advantages:
1.Design for CR-7, only use one screw hole.
2.No need other screw to install fan.
3.Won't be fused by hot head.
4.Nozzle fan makes effective benefits on bridge test.

Disadvantage:
1.Cover the path. If you want to use foldback clip to fasten the flat, you have to clip it in the right side.
2.You have to put this duct in the "good" position exactly, o