Advertisement
PRINCIPLES OF AIR SPRAY
Spray application is perhaps the simplest method of
coating where a sizeable area or volume of material
is involved or when intricate shapes and irregular
surfaces require painting. Spray will give the most
uniform film thickness making it easy to obtain a
smooth finish.
The air spray gun is a tool which uses compressed
air to atomize paint, or other sprayable material, and
to apply it to a surface. Air and material enter the
gun through separate passages, and are mixed at
the air cap in a controlled pattern. Air spray guns
may be classified in various ways. Two ways of
classifying guns are by the location of the material
container and the material feed system. Figure 1
shows a gun with a cup attached below. This is
called Suction Feed which draws material to the
gun by suction. Figure 3 is a gun with a cup attached
above. This is called Gravity Feed - the material
travels down, carried by gravity. Figure 4 shows a
material container some distance away from the
spray gun. This is Pressure Feed - the material is
fed by positive pressure. Suction feed is easily
identified by the fluid tip extending slightly beyond
the face of the air cap, as shown in Figure 2. Suction
feed guns are suited to many color changes and to
small amounts of material, such as in touchup or
lower production operations.
Figure 1 Suction Feed Gun with Attached Cup
Fluid
Tip
Figure 2 Suction Feed Air Cap
Air Cap
Figure 3 Gravity Feed Gun With Cup on Top
Gravity feed guns are ideal for small applications
such as spot repair, detail finishing or for finishing in
a limited space. They require less air than a suction
feed gun and usually have less overspray.
Figure 4 Typical Pressure Feed Gun With Remote
Cup
Figure 5 Pressure Feed Air Cap
A pressure feed system is normally used when large
quantities of material are to be applied, when the
material is too heavy to be siphoned from a container
or when fast application is required.
SB-2-001-F Page 3
Fluid
Tip
Air Cap
Advertisement
