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In automotive refinishing, a spray gun that produces an uneven fan pattern—especially spraying heavier on one side—is a clear indication of airflow imbalance or internal blockage. Even when using a high-performance LVLP Spray Gun Multi-Purpose Long-Lasting or a standard air spray gun, this issue can occur if maintenance or setup is neglected.
Root Causes of One-Sided Spray Pattern
The most common cause is a partially clogged air cap. The air cap contains multiple precision-drilled holes that control atomization symmetry. If even one side is blocked by dried paint or debris, the airflow becomes uneven, resulting in a distorted spray pattern.
Another possible cause is damage to the fluid nozzle. A dent or irregularity in the nozzle opening disrupts paint flow distribution. Additionally, improper fan control adjustment can also create asymmetry.
Step-by-Step Diagnostic Method
Start by removing the air cap and performing a visual inspection. Look for any blocked holes or dried coating material. Soak the air cap in cleaning solvent and use a soft brush to clean it thoroughly. Never use metal objects, as they can enlarge or damage the holes.
Next, rotate the air cap 180 degrees and perform a test spray. If the spray pattern flips direction, the issue lies in the air cap. If it remains the same, the problem is likely in the fluid nozzle or internal passages.
Inspect the fluid nozzle for wear or damage. Replace it if necessary, ensuring compatibility with the needle.
Professional Adjustment
After cleaning and replacing components, reassemble the spray gun and adjust the fan control. Ensure the fan pattern is fully open and balanced. Perform a test spray on a panel to confirm uniform distribution.
Preventive Measures
Regular cleaning is essential. Always flush the spray gun immediately after use and periodically deep-clean the air cap. Use filtered air to prevent contaminants from entering the system.
Conclusion
A spray gun that sprays on one side is not a random issue—it is a precise mechanical imbalance. By following proper diagnostic steps and maintenance routines, you can restore perfect spray symmetry and maintain professional-quality finishes.
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