Hitachi AA 2000 How the Air-Assisted Airless Spray Gun Operates, Select a Spray Tip and Air Cap

Operation

How the Air-Assisted Airless Spray Gun Operates

The air-assisted airless spray gun combines airless and air spraying concepts. The spray tip shapes the fluid into a fan pattern, as does a conventional airless spray tip. Air from the air cap further atomizes the fluid and completes the atomization of the paint tails into the pattern to produce a more uniform pattern. The pattern adjustment valve controls the width of the pattern.

Note that the air-assisted airless spray gun differs from an air spray gun in that increasing the pattern air reduces the pattern width. To increase the pattern width, less pattern air or a larger size tip must be used.

The spray gun has a built-in lead and lag operation. When triggered, the gun begins emitting air before the fluid is discharged. When the trigger is released, the fluid stops before the air flow stops. This helps assure the spray is atomized and prevents fluid buildup on the air cap.

Select a Spray Tip and Air Cap

The fluid output and pattern width depend on the size of the spray tip, the fluid viscosity, and the fluid pres- sure. Use the Spray Tip and Air Cap Selection Charts, on pages 18 and 19, as a guide for selecting an appropriate spray tip and air cap for your applica- tion.

NOTE:

DUsing a Fine Finish Spray Tip may improve the finish of certain urethanes, clearcoats, or light- weight air-dry enamels. Refer to the Fine Finish Spray Tip Selection Chart on page 19.

DIf you are applying a solid stream of fluid, such as mastics or sealants, refer to the Solid Stream Spray Tip Selection Chart on page 19.

DWhen spraying at fluid pressures below 500 psi (35 bar) or spraying light viscosity fluids, use optional fluid needle 220±413 (see page 20). The standard needle may not provide positive shut off at those pressures or for such fluids.

DWhen spraying acid catalyzed varnishes, use optional fluid needle 222±497 (see page 20). Using a standard needle may decrease needle life and leakage may occur.

Install a Spray Tip

WARNING

INJECTION HAZARD

To reduce the risk of a fluid injection injury, follow the Pressure Relief Proce- dure on page 7 before removing or

installing a spray tip.

Install a spray tip in the gun. The air cap and spray tip position determines the direction of the spray pattern.

Rotate the air cap (the spray tip rotates with it) as needed for the desired spray pattern direction. See Fig. 3.

Vertical Spray Pattern Horizontal Spray Pattern

Fig. 3

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