Air spray guns (pneumatic sprayer)
The paint is applied to an object through the use of an compressed-air pressurized spray gun. The spray gun has a spray nozzle, air cap & needle, and need air compressor about 4 – 7 bar. When the trigger is pressed the paint mixes with the compressed air stream and is released in a fine spray.
The conventional air spray gun is normally 4-7bar (60-100psi) pressure, and the air spray guns normally equip with one extra tank like 600ml, 1000ml, so you have to fill the tank when the paint is finished. but there’s a lot of paint was wasted because of its big output volume and the atomization is not so good. Compare to the HVLP or LVLP, it has less atomization and more waste.
Types of nozzles and sprays
Due to a wide range of nozzle shapes and sizes (tip size from 0.8mm to 2.5mm), the consistency of the paint can be varied. The shape of the workpiece and the desired paint consistency and pattern are important factors when choosing a nozzle. The three most common nozzles are 1.4mm / 1.7mm / 2.0mm in the shape of full cone, hollow cone, and flat stream. In a manual operation method the air-spray gun should be held by a skilled operator, about 6 to 10 inches (15–25 cm) from the object, and moved back and forth over the surface, each stroke overlapping the previous to ensure a continuous coat. In an automatic process the gun head is attached to a mounting block and delivers the stream of paint from that position. The object being painted is usually placed on rollers or a turntable to ensure overall equal coverage of all sides.
HVLP (High Volume Low Pressure) spray gun
This is similar to a conventional spray gun using a compressor to supply the air, but the spray gun itself requires a lower pressure (LP) for low overspray. A higher volume (HV) of air is used to propel the paint at lower air pressure. The result is a higher proportion of paint reaching the target surface with reduced overspray, materials consumption, and air pollution. A pressure regulator is often required so that the air pressure from a conventional compressor can be lowered for the HVLP spray gun. Alternatively a turbine unit (commonly containing a vacuum cleaner derived motor) can be used to propel the air without the need for an air line.
A rule of thumb puts two thirds of the coating on the substrate and one third in the air. True HVLP guns use 8–20 cfm (13.6–34 m3/hr), and an industrial compressor with a minimum of 5 horsepower (3.7 kW) output is required. HVLP spray systems are used in the automotive, marine, architectural coating, furniture finishing, scenic painting and cosmetic industries.
LVLP (Low Volume Low Pressure) spray guns
Like HVLP, these spray guns also operate at a lower pressure (LP), but they use a low volume (LV) of air when compared to conventional and HVLP equipment. This is a further effort at increasing the transfer efficiency (amount of coating that ends up on the target surface) of spray guns, while decreasing the amount of compressed air consumption.
LVMP (Low Volume Medium Pressure) spray guns
This is a new type spray gun which occured in the market in the recent years.
the LVMP medium pressure spray gun will generate better atomization than LVLP sprayer. but you have to attach it to one bigger horsepower compressor which would generate more compressed air for this spray gun