Spray Painting Equipment

Use and maintenance of refinishing equipment, spray guns, cups, compressors, regulators, hoses, spray booths, respirators is of the utmost importance, for to create a perfect finish definitely requires a solid knowledge of surface preparation.
But even an extensive knowledge of surface preparation techniques and paint chemistry is not enough to assure a professional finish. It must still be applied by a spray gun and all of the variables of its use must be controlled. The equipment necessary to apply the finish; the spray gun, cup, regulator, hoses, compressor, etc. must all be matched to the job and to each other. The equipment must be used and maintained properly, with an appreciation of how it works and why is works the way it does.
The moment of truth for any finish is when the trigger is pulled on the gun.

Installation - Spray gun                                  

Important: To ensure that this equipment reached you in first class condition, protective coatings have been used.Flush the equipment through with a suitable solvent before use.

1. Attach air hose to connector. Recommended hose 8mm bore. The hose must be conductive and electrical bond from the spray gun to earth should be checked with an ohmmeter. A resistance of less than 106Ω is recommended.
2. Air supply should be filtered and regulated.

1.1 Operation

1. Mix coating material to manufacturers instructions.
2. Turn needle adjusting screw counter-clockwise until first thread shows.
3. Turn pattern valve counter-clockwise to fully open.
4. Adjust inlet air pressure to give 2 bar (29psi) as the gun inlet with the gun triggered.
5. Test spray. If the finish is too dry, reduce airflow by reducing inlet pressure. If finish is too wet, reduce fluid flow by turning needle screw clockwise. If atomisation is too coarse, increase inlet air pressure. If too fine reduce inlet pressure.
6. The pattern size can be reduced by adjusting valve.
7. Hold gun perpendicular to surface being sprayed. Arcing or tilting may result in uneven coating.

1. The recommended spray distance is 150-200 mm (6”-8”).
2. Spray edges first. Overlap each stroke a minimum of 50%. Move gun at a constant speed.
3. Always turn off air supply and relieve pressure when gun is not in use.

Air Flow Valve
If the airflow valve is fitted this can be used to reduce the inlet pressure through the gun. Screw the Adjusting Knob in to pressure.

1.2 Preventative Maintenance

1. Turn off air supply and relive pressure in the airline, or if using QD system, disconnect from airline.
2. Empty coating material into a suitable container and clean the gun and cup, preferably in a gun wash machine.
3. IMPORTANT- the cup must not be cleaned or rubbed with a dry cloth or paper. It is possible to generate a static charge, by rubbing, which if discharged to an earthed object could create an incentive spark and cause solvent vapour to ignite. Only use a dampened cloth or antistatic wipes if additional cleaning is required in a hazardous area.
4. Remove air cap and clean. If any of the holes in the cap are blocked with coating material use a toothpick to clean. Never use metal wire which could damage the cap and produce distorted spray pattern.
5. Ensure the tip of the nozzle is clean and free from damage. Building up of dried paint can distort the spray pattern.
6. Lubrication- stud-screw, needle and air valve should be oiled each day.

2.0 Air Atomizing Spray Gun
A spray gun is a tool which uses compressed air to atomize paint or other sprayable material and apply it to a surface. Air and the material enter the gun through separate passages and are mixed at the air cap in a controlled pattern.
Spray guns can be classified in various ways. One is by the location of the container. Figure 2 shows a gun with an attached cup. Figure 3 illustrates a gun using material from a container some distance away. The type of material feed system can also be a way of classifying guns, with the material either kept under pressure – a pressure feed gun (figure 3) or using the suction feed principle to deliver the material to the gun (figure 2).

Figure 2 : Suction Feed Gun with Attached Cup

Figure 3: Pressure Feed Gun with Remote 2 gal. Cup
A spray gun design in which a stream of compressed air creates a vacuum at the air cap, providing a siphoning action. Atmospheric pressure on the material in the suction cup forces the material to the air cap of the gun. The vent holes in the cup lid must be open. This type gun is usually limited to quart-size or smaller containers. It is easily identified by the fluid tip extending slightly beyond the face of the air cap. Suction feed guns are suited to many colour changes and small amounts of material, such as in auto refinishing.

Pressure Feed Gun
In the design of the pressure feed gun the fluid tip is flush with the face of the air cap (figure 4) and no vacuum is created. The fluid is forced to the air cap by pressure kept on the material in the system: a separate cup, tank or pump. This system is normally used when large amounts of material are too heavy to be siphoned from a container, or when fast application is required. Production spraying in a manufacturing plant would be a typical use of a pressure feed system.
Figure 4 : Pressure Feed Air Cap

Bleeder Type Gun
A bleeder type gun is designed without an air valve. Air passes through the gun at all times. It is usually used with small compressors of limited capacity and pressure which have no pressure-controlled device such as an unloader or pressure switch. In this type of gun (figure 5) the trigger only controls the flow of fluid.
Figure 5 : Bleeder Type Gun 

Non-Bleeder Type Gun
A non-bleeder type gun is equipped with an air valve to shut off the flow of air when the trigger is released: the trigger controls both air and fluid flow. It is used with compressors having some type of pressure control device.
Figure 6 : Non-Bleeder Type Gun

External Mix Gun
This type, as shown in figure 7 mixes and atomizes air and fluid outside the air cap. It can be used for applying virtually all types of materials and is desirable for spraying fast drying paints such as lacquer. It is also used when a high quality finish is desired.
Figure 7 : External Mix Gun 

Internal Mix Gun
This gun type mixes air and material inside the air cap before expelling them, as shown in figure 8. it is usually used where low air pressures and air volumes are employed or where slow drying materials are being sprayed. A typical example would be spraying flat wall paint or outside house paint with a 1/4 or 1/3 HP compressor. Internal mix guns are rarely used for refinishing when very fast drying materials are being sprayed.  
Figure 8 : Internal Mix Gun

Airbrush
This is a very small, lightweight spray gun used for painting very fine detail such as stripes. It has a paint capacity of ½ to 1 ounce and the spray pattern is adjustable up to about the size of a 5c piece.
Figure 9 : Airbrush