High-visibility and performance Prusa MK4 fan duct

I created this model because I wanted a fan duct that could accomplish all the following things:

• Good performing cooling from all directions.
• Being able to easily observe the nozzle during printing from the front and from the left side, where my camera is mounted.
• Having the air blow (mostly) backwards so you don't get dry eyes when watching a print.

I made sure that this fan duct is compatible with my Automatic Nozzle Wiper and doesn't collide with the mechanism. This fan duct allows for easy observation of the wiping process and for easier alignment and troubleshooting.

The position, angle, and size of the fan duct openings are inspired by The Sweeper, which is a fan duct design that won this contest on the YouTube channel NeedItMakeIt.

Print settings

I uploaded a .3mf file for the door and the fan duct, which I recommend using because I have already marked the required positions for supports and custom seams. In general, I recommend using a 0.15 mm layer height for these parts.

For the door and fan duct material, I would recommend PC or PCCF (which I used) if you print with high-temperature materials. Otherwise, ASA is probably enough.
(I observed the fan duct printed from ASA slightly deforming when running a long PCCF print.) These two parts should be relatively stiff, so the fan duct openings don't have too much wiggle room.

You will also have to do a bit of post-processing on the fan duct:

• The opening supported by the support structures is intentionally 1 mm longer in the file than the other opening. This is because I recommend sanding or cutting the rough surface where the supports touched the part down a bit so that the surface is smooth.
• To allow for excellent cooling performance, the two openings are very low, so I also recommend sanding and/or cutting the parts of the fan duct that will be lowest when installed down to increase the gap between the printed part and the fan duct openings:

(Red marks the areas where sanding/cutting is required/recommended)

If you printed, post-processed, and installed the parts and feel like the fan duct openings are still too low, let me know in the comments, and I will create an additional version with raised openings.

Regarding the LoveBoard Cover, the only required modification is to cut out the corner where the raised print door would collide with it:

So realistically, you don't need to reprint this part, you can just carefully cut this out with a side cutter or something similar. If you break the part during this operation, or want it to look better, I also added the modified .stl of the LoveBoard Cover with the corner already cut out. This can be printed from PETG or PLA, since it's just a cover. Choose whatever settings you like the best here.

Required parts and assembly

The required screws are exactly the same as the original parts used, and the assembly can also be done in exactly the same order.

Performance

I'm aware that the fan duct The Sweeper was designed and tested with a stronger fan, so I don't expect it to have exactly the same performance.
I printed many parts with speeds up to 400 mm/s, general overhang tests, and my personal torture test, the Biblically accurate Benchy (see picture below). From that, I can say that I only had problems when printing steep overhangs at high speeds with thick layer lines, something other fan duct designs I tried also failed to do well.

Important note

This fan duct adds some resistance to the airstream, causing the print-fan calibration to fail if you have this mod installed, so if you need to pass the test, just unscrew the fan duct and reinstall it after running the test.

Inspirations

• The cover of the door for the fan cables is inspired by the Improved MK4 Fan Door.
• The splitter design for the airstream coming out of the fan is inspired by the Improved MK4 Fan Duct.