In an effort to minimize the moving mass of the print head and because the noisy 5015 fang I was using was blocking precious airflow from the 30mm cold end fan's radiator I've created an air jet nozzle that connects to an external AIR COMPRESSOR!
First thing you'll need is the compressed air, and I recently gutted a dead 2005 Japanese massage chair and discovered a tiny super quiet 120v air compressor, so I now have some relatively low pressure compressed air available in my home. Since the goal is to get a jet of air aimed just below the hot nozzle, I figured I would generate a straight nozzle in OpenSCAD and then chop away in 3D Builder to get it in the right shape and mounted to the printer.
It works REALLY well. I tested the jets with a dish of water and it created perfect divots, and during printing bridging was perfect. I shut the air off during the print and edges started curling up, so definitely doing it's job. The main downside is the LOUD noise of the jets of air hitting the part, especially tubular objects. Just think of the hissing sound of a jet of air, escaping from a tire valve for example, and it changes and varies depending on where the jet is aimed on the part. You will have heard this sound to a lesser degree if you've used a good blower and fang type of arrangement.
The tubing I'm using from the chair is 9.5mm OD and 6.5mm ID. The air compressor found in old massage chairs that I'm using only puts out about 25psi, so if you connect this nozzle to your existing SHOP air supply, you'll probably need some sort of regulator / valve setup to adjust the pressure and flow. The chair had a bunch of 12v solenoid valves too, so I'll be working on having the printer's 12v fan output control them, possibly in a way that has multiple pressure levels, as well as connecting it to my delta so the one compressor feeds two printers.
I don't have the stock single extruder hot end, but if anyone has a need and measurements or knows of STL files of it, then I can create a version with a single nozzle.
0.2mm layers x 0.4mm nozzle
3D Solutech PLA
Setting the support angle to 90 degrees works for this print to keep Cura from making supports inside the air tube. PLA is fine for this part since it doesn't sit close to any heater, although PETG will hold up better in the long run if you have it.