This is my design of a new part cooling nozzle for my Monoprice Maker Select v2. This is the Mk IV, Mk I, II, and III where the prototypes and were very ugly to say the least. A lot of learning came from those to make the Mk IV a reality.

The Mk IV is designed based on the inversion of an airplane wing to create a low-pressure zone on the inside of the circle, near the nozzle. This will draw in cooler air from above the nozzle and combine it with the air coming out of the cooler from the parts fan.

I say inverted airplane wing because in the ring I create a small venture effect to increase the air pressure, then direct the air out at an extreme angle to accelerate it. As the air accelerates, it starts to drop in pressure, which then requires more air to come in and fill the void. At the bottom of the ring, on the inside close to the nozzle, this new combined airflow is directed to a point about 2mm below the surface of the cooler. This should place the main bulk of the airflow right at the interface of the hot filament coming out of the hot-end and the already existing plastic of the part. The calculation for this was, well, none. I created a vapor that allowed me to observe what was going on.

The result is more air flow with less RPM of the fan and not having to get a massive fan to move more air for more cooling! The thought is to do more with what you already have by using science!

The air is designed to come out in a circle, that when it meets just below the nozzle, it will create a small circular swirl of the air to help move the now hot air away from the part and help cool faster.

The fan is moved to a horizontal mount above the plane of the mounting bulkhead. This is a direct result of me hitting the part cooling fan with tweezers and having to replace the fan because blades went flying. Pesky tweezers! Also, I didn't want to suck in the hot air coming right off the heated bed, so moving this to a horizontal position on top of the entire assembly brings the fan into cooler air away from the bed.

This is designed to be printed in one of two ways. If you are brave and good with supports, the Base-Shroud file is the entire base and shroud as one piece. You will need supports for the mounting bulkhead. The ring must be printed upside down. The inner part of the ring is about 2mm shorter than the outer part, this will lead to noodles from the filament instead of a nice part.

One thing to note is that the interface between the shroud and the base has a small "wing' in it to not only split the airflow going into the ring, but also allow for printing of this section without supports and crazy bridging. You can see this feature in the two cross-section photos.

Speaking of the cross-section, the upper part of the ring, the piece that is printed separately and upside-down is colored red to easily see why it needs to be upside-down and to distinguish it from the base assembly. You can also see what my though process is for the inverted wing.

All the screw holes are designed under-sized to allow for the use of an M3 tap to cut the threads. You can just use the screws to cut the threads, but this often leads to a stripped screw hole. If you have M3 inserts, you can use the holes as a pilot to drill the proper sized holes for your inserts and epoxy them in.

Otherwise, the base and shroud are separate, and the shroud is split in two to allow for printing with no supports. This will require a little more finishing and sanding to get everything to fit just right again, but if you wish to go this route the option is yours.

I am not making any scientific claims with this part or design, just my own observations and explanations of what is going on and why I made the design decisions I did. If someone wants to provide more of a scientific explanation and knows fluid dynamics much more than I do, please leave a comment.