Air-Assisted Airless Spray System

Air-assisted airless spray systems were developed to offer the production capacity of an airless system along with the fine atomization that conventional air spray can provide. This system operates very much like an airless system. The difference is that the gun has a small compressed air line running to it. It appears like a conventional gun but the compressed air supplied completes atomization rather than creating it. The system is set up in a way that just enough airless atomizing pressure is created to make an incomplete spray pattern (one with tails or fingers at the edges). The compressed air stream (low 20 psi) is directed across the spray pattern right at the tip. This small curtain of air completes the spray pattern and provides for soft edges and a finer atomization of the paint without increase in pressure. The transfer efficiency is quite high (60 to 70 %) and the production rate is that of a typical airless system.

Typical Air-Assist Airless System

Advantages of Air-Assisted Airless

Fine Atomization: Very good atomization, almost as good as air spray and better than straight airless. Wood and metal finishers like the smooth breakup of the coatings.

High Production: Air-assisted airless can be set up to have the speed of a traditional airless or be set up (smaller tips and lower pressures) to act like a high production air spray system.

Good Transfer Efficiency: Because Air-assisted airless works generally at lower pressures than a standard airless, the penetration is better and rebound is less. Transfer efficiency can be as high as 70 %, although 50 to 60% is typical.

Adjustable Fan Size: some manufacturers have made the gun to have of an adjustable fan. By using the compressed air going to the air cap, the fan can be compressed to a smaller size by jets of air on either side of the airless tip. This adjustment can reduce the size of the fan approximately 50%.

Disadvantages Of Air-Assisted Airless

Safety: Because of the extreme high pressures (1000 to 3000 psi) created by the Air-assisted airless pump there is a danger of injection injuries. The pumps, lines, and guns must be manufactured to withstand these pressures. The guns themselves must be manufactured with trigger guards, trigger locks, and tip guards. The painter or finisher must also have complete safety training before using the equipment.

Expensive: The pumps, lines, guns and accessories are designed to handle and produce extremely high fluid pressures. For this reason the equipment has to be well made and strong. Typical Air-assisted airless systems are more expensive than air spray systems and the maintenance costs are higher.

Gun Controls: Even though some Air-assisted airless guns allow for some fan width control the gun is still a typical airless configuration. The trigger is still full on/full off and there is no feathering of the trigger possible. To change the fan size (dramatically) the tip must be changed. To increase or decrease fluid output the tip must be changed.

Tip Plugging: Tip orifice size can range from .009 inch to .065 inch. The typical or common sizes range from 11/1000" to 21/1000." The coatings used must be properly strained and the machine filters clean and the right size to prevent excessive tip plugging.