In airless spray applications, the paint is pressurized between 5 atm and 35 atm and sprayed from the nozzle of the airless spray gun. As the spray pattern, which comes out of the nozzle in a thin curtain and at high speed, hits the stagnant air molecules outside the gun, it ruptures and turns into droplets.
The size of the droplets,
- As the paint output speed increases,
- As the paint pressure increases,
- As the paint viscosity decreases and
- The surface tension of the paint decreases as it decreases.
The size of the pattern depends on the hole size and shape. However, in airless spray applications, the atomization quality of air spray applications cannot be reached. While the diameter of the paint droplets sprayed from the nozzle of the spray gun reaches the range of 20-50 µm in air spray applications, this value is in the range of 70-150 µm in airless spray applications. On the other hand, as you go from the center to the edges of the spray pattern in air spray applications, the decrease in paint droplets allows smooth transitions between applications. Therefore, it becomes easier to make applications with homogeneous thickness. In airless spray applications, they do not give this chance because they do not contain air. It is more difficult to apply uniform thickness with airless spray applications.
In terms of application speed, airless spray applications provide faster application. However, on uneven, complex surfaces, it may cause the paint to fall thickly and to sag.
In airless spray applications, since there is no compressed air accompanying the paint droplets, the amount of solvent that evaporates before the paint reaches the surface is less. This causes the paint to fall more wet on the surface. For this reason, faster evaporating types should be used both in the selection of solvents in the paint formulation and in the selection of the application thinner.
Compared to air spray applications, airless spray applications have less bouncing effect and therefore less paint particles spreading to the environment. Therefore, the transfer efficiency is relatively higher.
There are also cases where air assisted but airless systems are used. In these systems, the pressure is more than the air pressure in the air spray systems and less than that of the airless system. In such systems, atomization is much better than the airless system.