QiDi Max4 (X-Max 4) Aux Fan Nozzle

From the factory, the Aux Fans on the QiDi Max4 do nothing.  They blow almost directly upward to the top glass, instead of sending supplemental cooling air across the print area.  The first place I became aware of the issue was in a YouTube video by Crizs Creations (video at the bottom, to keep text tidy, and thanks to the creator who reached out to jog my memory as to where I had seen the issue reported first).  This was before I had my machine, and before I was able to perform my own tests.  We came to different conclusions about the root cause of the issue, but after performing brief testing on my machine I was able to confirm the findings present in the video.  However, regardless of the root-cause diagnosis, the solution would be the same: an air ducting nozzle.  Not seeing any solutions yet, I felt that it was in need of fixing.

The problem arises from the fact that the aux fan housing just dumps all airflow out of a cut-open corner, with only a bevel along the back corner to help turn the air.  Air doesn't flow like that, so the jet of air is just a wild blast blowing 60º up and out.  This nozzle dams the air along the top of the housing, forcing it to flow out and across the print area.  In order to keep things from spilling downward, it also dams against the housing along the bottom of the cut, and juts slightly forward of the upper wall.  The profile of this jut follows the face angle of the pillar supports to aid in printability.  Some air does still spill downward, due to the fairly short guide path dictated by the relief required for the print head along the side.  This could possibly be resolved by adding an upward taper to the top edge of the nozzle, but I'm moving on.  EDIT: A person could also try re-profiling the lower lip to remove the slope and add a reverse-bevel to the bottom.  It's likely that the slope at the exit is pulling the air stream downward.  THIS IS CONFIRMED - it's been bugging me that I didn't just test this myself, so I took the lower lip off with a belt sander.  The downward draw of the air stopped.  The angle on the lower lip is acting as a spillway that the airflow is sticking to and partially diverting.  It wasn't a huge draw, but it was undesirable.  Either flattening or knife-edging the bottom edge of the outlet solves the problem.  This poses a challenge, as the front face is very thin (2mm - the maximum space allows), the bottom section of the pillar notch is required for the bottom air dam tabs, and removing the bottom lip also makes printing more challenging due to less surface area as well as edge thickness issues with high-temp materials.  Tricky, but not impossible.  I'll leave it as a tweak for others to integrate - this version of the design works for my purposes.  /EDIT

The example in the pictures was printed from ASA with supports on the cut bevel surface.  There is a version without this bevel cut, which does not require any supports to print.  However, the non-cut version does obscure some of the camera view - specifically, it obscures the area where the print head parks over the waste chute (pictured).  If you don't watch the camera in Fluidd, the non-cut version functions slightly better along the forward-edge of the print bed and is easier to print.  For printing, the easiest and simplest way is to orient the part with the front face (air exit) on the bed.  If you're a wizard with support tuning, you could orient the part with the front face upward as the final print layer, to get a nice surface on all visible areas.  Additionally, be sure to print in a material capable of withstanding the very high chamber temperatures these printers can reach (65ºC isn't actually the limit, especially on long, hot prints).  ABS is the bare minimum.  Be sure to record your shrink scaling in your slicer before printing the whole thing.

Strong supplemental air can be felt for the first third of the print area, tapering off to a light breeze at the far end.  With some rework this could likely be improved a little bit, but not a ton.  To improve bed reach much more would require designing a new back panel for the fan housing to properly guide the air into turning 90º before hitting the nozzle.  I put five support ribs in each long nozzle section purely because that was the first number to pop into my head.  Fewer support ribs could also improve airflow a bit, by reducing the small restriction they cause.  Give it a shot!

Fitment should be snug.  Depending on the exact placement of the pillar mounts on your machine, you might need to adjust the location of the locating notches by half a millimeter or so in either direction - easy enough to do in pretty much any CAD/modeling software, just be sure to do it symmetrically.  Currently, the notches are spaced equi-distant which should work with most builds, maybe with some slight hand-finishing.  Removal should require taking the small screwdriver that came with the printer (or any tiny screwdriver, really) and wedging it behind the notch face plates, in front of the pillar mounts (see pic).

I'll likely begin working on a new back plate for the aux fan housing in the near future, mostly because I need to retrieve a gauge I dropped back there by accident.  I sincerely hope somebody else beats me to it.

I'm releasing this under an non-commercial license because I want people to come up with their own respins and share them just as freely.  The basic geometry is there, now get to tweaking!  STEP files are included for importation into your favorite CAD software.  Fix my oversights and uncreative aesthetics!