DeVilbiss HVLP Gravity Feed Spraygun Spécifications télécharger pdf (Page 11)

34. What is the proper technique

for spray gun stroke and

triggering?

The stroke is made with a free arm

motion, keeping the gun at a right

angle to the surface at all points of

the stroke.

Triggering should begin just before

the edge of the surface to be

sprayed. The trigger should be held

fully depressed, and the gun

moved in one continuous motion,

until the other edge of the object is

reached. The trigger is then

released, shutting off the fluid flow,

but the motion is continued for a

few inches until it is reversed for

the return stroke.

When the edge of the sprayed

object is reached on the return

stroke, the trigger is again fully

depressed and the motion

continued across the object.

Lap each stroke 50% over the

preceding one. Less than 50%

overlap will result in streaks on the

finished surface. Move the gun at a

constant speed while the trigger is

pulled, since the material flows at a

constant rate.

Another technique of triggering is

referred to as “feathering.”

Feathering allows the operator to

limit fluid flow by applying only

partial trigger travel.

35. What happens when the gun

is arced?

Arcing the stroke results in uneven

application and excessive over-

spray at each end of the stroke.

When the tip is arced at an angle of

45 degrees from the surface (see

figure 19), approximately 65% of

the sprayed material is lost.

Figure 19 - Spray Techniques

36. What is the proper spraying

sequence and technique for

finishing applications?

Difficult areas, such as corners and

edges, should be sprayed first. Aim

directly at the area so that half of

the spray covers each side of the

edge or corner.

Hold the gun an inch or two closer

than normal, or screw the spreader

adjustment control in a few turns.

Needle travel should be only partial

by utilizing the “feathering”

technique. Either technique will

reduce the pattern size.

If the gun is just held closer, the

stroke will have to be faster to

compensate for a normal amount

of material being applied to smaller

areas.

When spraying a curved surface,

keep the gun at a right angle to

that surface at all times. Follow

the curve. While not always

physically possible, this is the ideal

technique to produce a better,

more uniform, finish.

After the edges, flanges and

corners have been sprayed, the

flat, or nearly flat, surfaces should

be sprayed.

Remember to overlap the

previously sprayed areas by 50%

to avoid streaking.

When painting very narrow

surfaces, you can switch to a

smaller gun, or cap with a smaller

spray pattern, to avoid readjusting

the full size gun. The smaller guns

are usually easier to handle in

restricted areas.

A full size gun could be used,

however, by reducing the air

pressure and fluid delivery and

trigger-ing properly.

MAINTENANCE

37. How should the air cap be

cleaned?

Remove the air cap from the gun

and immerse it in clean solvent. If

necessary, use a bristle brush to

clean dried paint. Blow it dry with

compressed air.

If the small holes become clogged,

soak the cap in clean solvent. If

reaming the holes is necessary, use

a toothpick, a broom straw, or

some other soft implement (see

figure 20).

Cleaning holes with a wire, a nail or

a similar hard object could

permanently damage the cap by

enlarging the jets, resulting in a

defective spray pattern.

Figure 20 - Cleaning the Air Cap

2. Air Atomizing Spray Guns (Cont’d)

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