Airless spray painting is a term commonly confused and compared with/to different forms of conventional spray painting.
Simply put, airless spray is the process of atomizing paint with pressure. With conventional spray, air is injected into the spray cap to atomize the paint. The conventional spray gun then needs to be setup and adjusted in order to achieve a desired spray pattern. In airless spray, an airless spray pump is used to pump paint at a high pressure to a spray gun where it is then atomized through a spray tip. As the paint emerges from the spray tip it is essentially a solid stream travelling at a high speed which is then broken down into small droplets by the resistance of the atmosphere. The process is similar to that of you putting your finger in front of a garden hose in order to create a spray effect. It is important to remember that factors like the viscosity of the paint and temperature will also play a role in atomisation. Airless spray tips come with set parameters which determine the spray pattern. In order to change the spray pattern, all that you will needs to do is swap the spray tip. For more information on how to select the correct spray tip for your application read our article ‘Spray tips – How to choose the right size?’
Paint being atomized as it leaves an airless spray gun
There are three different types of pumps that can be used for airless spray:
- Electric pumps (plug into a 220V socket)
- Petrol pumps
- Pneumatic pumps
Generally speaking, the pressure required at the spray tip in order to atomize paint is between 80 to 180 bar. Electric and petrol pumps can produce about 230 bar, while a pneumatic pump can produce up to 500 bar depending on the model.
Airless spray painting has many advantages. Because of its speed it is ideal for large projects and spraying large surface areas. Airless applications usually result in lower overspray and achieve a transfer efficiency of 60% to 90% resulting in a high DFT. With the high pressure of airless spray, high viscosity coatings can be atomised without costly solvent reduction. Airless sprayers produce an even coat of paint on all surfaces leaving a high-quality finish. Another advantage of airless spray is not having to adjust and setup the spray gun in order to achieve a certain spray pattern. A simple swap of a tip does the trick!
There are, however, a few setbacks of airless spray to take into consideration. Airless spray equipment takes time to flush and clean before it can be stored or used again. Airless spray equipment makes use of wearable parts that will need to be replaced at an extra cost. Although airless spray is great for floors, roofs, steel construction and other industrial applications, it is not ideal for fine finish applications. Conventional spray still produces a higher quality atomisation ideal for finer applications.