UPDATE March 16, 2019: Included a shorter model to just use the bottom two screws like I do. Less wasted plastic, prints quicker. Have not tested it but no other changes were made so it should work fine. Filename: "FanDuct_Modified_v1_Short.stl"
"FanDuct_Modified_v1.stl" - Original remix (use all four fan screws or just the bottom two)
"FanDuct_Modified_v1_Short.stl" - Shorter/quicker version (use only bottom two screws, do not use the top two fan screws!)
This is a remix of the excellent fan duct designed by misterpepper, the "Ender 3 EZ Vent Upgrade"
The original design featured severe bridging at both air outflow ports which would cause sagging and ultimately deform airflow. In addition there were multiple horizontal design elements in the ducting itself which would cause bridging - these were removed. Vertical support blades were added inside both air outflow ports to A) eliminate bridging/sagging in these areas and B) improve directional airflow to the printer nozzle. This design prints great with no supports and only a skirt, and limits waste by not having to print a second one to get a quality duct (as suggested by the original duct design).
NOTE: When installing I recommend only using the bottom two screws, this helps keep the duct from being torqued toward the bed. Print with the fan duct sitting upright on your print bed (see photos, bottom of duct flat on your bed). Use a high temperature PLA/PLA+ (I used 3D Solutech Silver) or ABS/PETG for extra temperature security. I had the best luck with PLA. No supports are needed, and I printed mine with a skirt. When using this duct ensure your fan is set to 60% or higher after your first layer to prevent warping during long prints and improve overall print quality.
Planned updates include integration for a mini-LED to light prints, and potentially a version compatible with 5015 fans. If you have design suggestions let me know. I will also be experimenting with increasing the air outflow angle.
3D Solutech PLA
Print in a high temperature PLA, PETG, or ABS. I printed mine at .12 mm layer height with 3 walls/perimeters, 30% infill at 60 mm/s.
Photo of vertical support blades in each air outflow port to eliminate sagging and improve airflow.
Section analysis of the fan duct to show vertical support blades and removal of horizontal structures in the original duct design.