|Paint Spraying - Choosing a System
Paint Spraying Step by Step
Back to Spraying & Painting
In general, all spray systems perform the same tasks, therefore the type of system
to choose depends on what, how much and how fast you plan on spraying. Every set-up
has three essential components: a gun which sprays the finish, a cup or pot which hold
the finish and a power system (air compressor) which moves the finish through the gun
and atomises it at the tip.
Spray Gun Selection
Regardless of the variety and sizes of spray gun, they are basically the same – they contain inlets for air and fluid, fluid needles and tips and an air cap.
See: How Spray Guns Work
The airline/hose from the air compressor attaches to the gun and fluid enters the gun from a pot/cup mounted directly to the gun. Screws located on the back of the gun can adjust the fluid and air flow. There are two major types of spray gun: suction-feed and gravity-feed.
Suction Fed Spray Guns
There are several ways to identify this type of gun quickly.
The material container or pot is located below the gun, the lid to the container
will have vent holes and the fluid tip extends just beyond the face of the air cap.
Spraying is achieved by compressed air entering the gun and moving through it to
create a vacuum at the air cap. Outside air is allowed to enter through vent holes on
the pot lid. The difference in air pressure produces a siphon that draws material up
the fluid tube and into the gun. The material is drawn through the fluid tip where it
mixes with the air coming from the cap and is atomised.
See: How Spray Guns Work
Gravity Fed Spray Guns
These guns can be easily identifiable by the material cup, which is located at the top of the gun.
The force of gravity allows the material to flow down into the gun, eliminating the need for a fluid tube.
Like suction-feed guns vent holes allow air to pass through the top of the cap ensuring constant flow of material.
Since no atomising air is required to move material, gravity guns are more efficient than suction-feed and also
require less compressed air.
Suction-feed guns are ideal for small to medium projects and can be used in many different positions such as overhead spraying. Gravity-feed guns are lighter and give better balance, which takes the strain of the operator’s wrists.
Air Compressor - The Power Source
Reciprocating air compressors basically compress atmospheric air to a given capacity and pressure. The type of unit will depend on the spray gun selected and the number of guns to be used at any one time. For the hobbyist a complete spray system can be purchased including the spray gun, hose complete with connectors and the air compressor. Guns that are purchased separately will display the average air consumption in CFM (cubic feet per minute) and pressure in either Bar or PSI (pounds per square inch). A compressor can then be purchased ensuring the FAD (free air delivery) of the unit and the pressure is equal to or more than the air consumption of the gun.
Lubrication free compressors are better for paint spraying as there will be no contamination of the paint while spraying.
See: Choosing an Air Compressor
To connect the Spray Gun to the compressor you will need a selection of couplings, fitting and high pressure hose, quick release couplings should also be used, these allow the hose or gun to be disconnected safely without any loss of air from the system.
See: Airlines, Filters & Couplings
When spraying any material whether water or solvent based it is
important to wear a nose/mouth mask or respirator.
It is vital when purchasing these products to inform the vendor of
the type of material being sprayed as wearing the wrong masks is as
useful as wearing no mask at all.
Other equipment is optional such as overalls and shoes. Protective
goggles are advisable due to over spray especially for spectacles
wearers. In many cases the manufacture of the finishing material will
indicate the protective measures such as facemasks, gloves, goggles,
etc. However, if in any doubt the manufacturer should be contacted.