High volume/low pressure (HVLP) spray guns are designed to promote the atomization and material flow of paint materials such as water-based metallic colors and acrylic clear coats. To achieve a professional finish, HVLP guns must be adequately adjusted to optimize paint application. There are three different adjustments to consider.
Air Pressure
The small turning screw at the base of the spray gun handle controls air pressure. If the air pressure is too high, excessive overspray is created resulting in a rippled, orange peel-type finish. If the pressure is too low, the paint may not atomize correctly leading to spotting or a cobweb effect.
Width of Fan
The turning screw to the side of the spray gun next to the air cap controls paint fan width. If the paint fan is too narrow, paint is forced out at a higher pressure makings the crossing of coats more difficult. Often, a narrow fan results in runs and sags. If the fan is set too wide, cross coats may not join together suitably and this will lead to a dry, dust-like finish.
Volume Adjustment
The turning screw at the back of a spray gun controls material volume, instrumental in promoting adequate flow. If the screw is twisted too far inward, material flows slowly and the painting process takes long. This results in some sections of the paint curing while the rest of a vehicle panel is being painted, utimately ruining the final finish. If the screw is twisted too far out, excessive material is applied and, if the air pressure is not correct, this leads to the paint finish running.
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