After having downloaded and printed many "possible" air support units... for our Scuola++ laser cutter I decided to make my "best one", perfectly compatible with our new Ortur Laser Master 20W.
Please consider that other laser diodes (7W, 15W) might not be compatible, given the different physical AND laser characteristics. The LU20W diode works best in a focal distance range between 30 to 40mm from laser base to object (LU7W is 80-100, LU15W is 70-80mm).
For the original 15W unit, that I modified and "upgraded", please refer to my friend Brian Dragtstra and his website.

The idea is that during engraving or cutting materials with the Ortur Laser Master 20, smoke is created and this smoke enters between the material to be cut and the light source, so that the light no longer 100% reaches on the surface to be cut. If the smoke is very thick, up to 70% of the light beam can be absorbed into the smoke, reducing the laser power by 70%.

An Air Assis system provides a continuous flow of air that, like the laser, radiates perpendicularly downwards, blowing smoke aside instead of rising straight up. As a result, no smoke is released into the light beam, and the laser retains its full power. Moreover far less material burns will be visible, producing better quality prints.

A small radial fan (model "5015", easy to buy and cheap), through the 3d printed unit, directly blows air below the laser beam. Because the beam must enter the head from above, there is also a small hole at the top, through which the light can enter. This hole looks as if it obstructs the airflow, but it is not. A small amount of air leakage on this side is even desirable, so that smoke that rises above the head is also blown away. This keeps the entire light path of the laser free from smoke.

Another important detail of this design is that space has been kept for the user to focus the laser.

The 3D printed unit is held in place with rubber bands (see the pictures).

The electricity used can be taken from the power supply of the machine. In my case I soldered a jumper on the top of the laser diode tower (see the photos), so to take the same 12V power that reach the existing laser LED fan and use for the new fan as well (absorbed power is very low). This way the fan only works when the original laser fan runs as well, probably the best option.
Using the jumper "trick" I can easily detach (or substitute) the new fan from the air unit.

Remember to put the spacer, as shown in the photo, so to allow the machine to correctly initialise the (0, 0) position, having the head touching the end-run pin. Otherwise the head on the Y axis would keep on going against the X axis.

Here a list of what you need to print and buy...

PRINT

• Air support unit, with fan interface
• Laser diode cap, with nice Ortur logo, to better manage the rubber bands
• Little spacer (you can use whatever object sized 10x10x3mm).

BUY

• A "5015" 50x50x15 12V coaxial brushless fan, that you can easily order on gearbest or amazon:
  Gearbest link
  Amazon link
• Eventually a Dupont crimper and jumpers to ease the fan attachment to the laser power (you need to know how to solder). You can buy a set on Amazon...