The Twin Turbofan is made to fit the stock CR-10/Ender 3 (MK8/MK10) hotend and the stock heat sink cooling fan. It simply requires two 5015 fans, four M3 x 20mm as well as four M4 x 20mm button head screws and one M3 x 8mm screw (preferably socket head). It also requires 4 M4 Nuts (preferably thin - approximately 2mm depth).
Default orientation of the STLs is best for printing.
RADIAL FAN BRACKET:
The actual fan bracket/fang is a very complicated part and should be printed solid as this is a structural part that needs to be strong.
PETG or ABS are your best options due to the fangs being so close to the hotend but PLA can be used. I actually printed mine in eSUN PLA+ as that's all I had at the time and it still works fine but if I had the option I would definitely use PETG.
Supports are definitely required and i found that Cura's experimental tree supports with a branch angle of 40 degrees worked quite well as they all attach to the print bed and not lower areas of the part (this could probably also be achieved with standard supports set to only touching the build plate). I also recommend using a brim for this part.
This part should also be printed slow (around 30-40mm/s).
MOUNTING BRACKET AND FAN GUARD:
The mounting bracket and front fan guard are totally fine to be printed in PLA, with the mounting bracket requiring simple supports and the fan guard requiring none.
You can print these pieces solid but you don't have to.
The top left edge of the left fan bracket (when looked at from the front) can potentially rub against the head of the screw on the metal bracket that the hotend attaches to. This manifests as quite a loud vibration during printing and can be eliminated by filing down that corner or as a more temporary solution, simply wedging a folded square of paper in there.
If you intend to run the 5015 fan wires through the radial fan bracket like in the above photos please read. To avoid making the same silly mistake that I did the first time around, DO NOT solder the fans in untill you are completely happy with all parts and the whole thing is assembled. Once the fans are soldered like this you will not be able to fit the fans through the gaps that the wires run through and to remove the fans from the bracket, you will have to destroy the bracket or cut the wires.
Please feel free to comment any suggestions or problems and I hope you enjoy!
eSUN PETG, PLA+