A spray gun is the "pen" of painting construction. A suitable spray gun with correct parameters can make the paint surface smooth and even; otherwise, orange peel, sagging, and particles will follow one after another. This article explains selection clearly from two dimensions: feed method and atomization technology, and provides the adjustment logic for air pressure, fluid output, and fan pattern.
In a nutshell: Gravity-fed/suction-fed determines material supply, HVLP/LVLP determines atomization efficiency; set the three major parameters (air pressure/fluid output/fan pattern) according to the coating, then combine with proper gun movement to get a good finish.
I. Feed Method: Gravity-fed vs. Suction-fed
Type
Principle
Features
Gravity-fed
Paint cup on top, relying on gravity + suction
Stable paint output, paint-saving, easy to clean
Suction-fed
Paint cup below, relying on airflow suction
Large capacity, suitable for prolonged operation
Figure: The difference in feed structure between gravity-fed (cup on top) and suction-fed (cup below) spray guns.
II. Atomization Technology: HVLP vs LVLP
HVLP (High Volume Low Pressure): High transfer efficiency (>65%), less paint rebound, eco-friendly and paint-saving, mainstream for repair.
LVLP (Low Volume Low Pressure): Requires less compressed air, suitable for small compressors, and friendly to delicate parts.
III. How to Adjust the Three Major Parameters
Air pressure: Refer to coating recommendations (clearcoat often 2–3 bar, basecoat lower); too high easily causes dry spray, too low causes sagging.
Paint output: Controlled by knob, matched with air pressure and gun movement speed, for even application.
Fan width: The larger the fan width, the wider the single pass; after adjustment, use a test spray panel to check whether the spray pattern is symmetrical.
Figure: After adjusting the three parameters, be sure to test spray—check that the pattern is symmetrical, edges are soft, and there is no center buildup.
Application key points: Each time you change paint or brand, re-test spray; use clean, dry compressed air (with oil-water separation); clean the spray gun immediately after use to prevent curing and clogging.
Summary
Spray gun selection depends on feed type (gravity/suction) and atomization (HVLP/LVLP); construction quality relies on air pressure, fluid output, and fan pattern matched to the coating and verified by test spraying. Only with clean air supply and timely cleaning can a stable orange-peel-free, sag-free finish be achieved.
Frequently Asked Questions (FAQ)
How to choose between HVLP and LVLP?
HVLP offers high transfer efficiency, saves paint, and is eco-friendly, making it the mainstream for repair work, but it requires a larger air source; LVLP consumes less air, making it suitable for small compressors and fine parts. Choose based on air source capacity and type of work.
Which is better, gravity-fed or siphon-fed?
Gravity-fed provides stable paint output, saves paint, and is easy to clean, suitable for fine touch-ups; siphon-fed has a larger cup capacity and allows continuous spraying for extended periods, suitable for large areas. Neither is absolutely superior—it depends on the working conditions.
What pressure should a spray gun generally be set to?
There is no universal value; follow the coating manufacturer's recommendation. Clear coats are often at 2–3 bar, while base coats are usually lower. Too high causes dry spray, too low causes sagging; always test spray first to confirm the spray pattern.
Why test spray every time you change paint?
Different coatings have different viscosities and solvent evaporation rates, requiring re-matching of pressure/paint output/fan width. Test spraying reveals issues like asymmetric pattern, dry spray, or buildup before working on the actual part, avoiding wasted pieces.
Why clean the spray gun immediately after use?
Residual coating will cure and clog the nozzle and needle valve, affecting next time's atomization precision. Especially two-component (2K) coatings become extremely hard to clean after curing, so they must be thoroughly cleaned with compatible solvent promptly after use.
Kexin New Materials · Automotive Coating Technology Library | This article is technical Q&A content, for reference in selection and construction
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