Finish defects should be diagnosed systematically. Randomly increasing air pressure or adding thinner may hide one symptom while creating another. Begin with the coating, then check the air supply, spray gun condition, setup, environment, and operator movement.
1. Orange peel
Orange peel appears as a textured surface instead of a smooth film. Common causes include coating viscosity that is too high, insufficient atomization, excessive spray distance, fast solvent evaporation, or poor flow before the film begins to cure.
With a LVLP SPRAY GUN, confirm that the nozzle is suitable for the coating and that dynamic inlet pressure is within the approved range. Reduce viscosity only within the coating supplier’s limits. Keep the gun perpendicular, shorten the distance if the surface is receiving dry droplets, and verify booth temperature and airflow.
2. Runs and sags
Runs occur when too much wet material accumulates or the coating cannot hold on a vertical surface. Causes include excessive fluid flow, slow travel speed, close spray distance, too much overlap, or over-thinning.
Reduce fluid delivery in small steps and increase travel speed while maintaining a wet, continuous pass. Apply lighter coats to edges, profiles, and vertical panels. If one operator repeatedly creates runs, compare movement and overlap with the approved setup card before changing the equipment.
3. Dry spray and rough edges
Dry spray occurs when droplets partly dry before reaching the surface. It may come from excessive pressure, long spray distance, hot booth conditions, strong airflow, a fast thinner, or poor gun angle. The surface can feel rough and may show low gloss.
Lower pressure gradually, move closer within the recommended working distance, and select the correct reducer for the booth conditions. A correctly adjusted LVLP SPRAY GUN should produce a wet, controlled fan without high-velocity bounce-back.
4. Uneven or split spray pattern
A heavy top, heavy bottom, or split fan often indicates blocked air-cap holes, dried coating around the nozzle, a damaged fluid tip, or poor alignment. Rotate the air cap: if the defect rotates with it, clean or replace the air cap. If the defect remains in the same position, inspect the fluid nozzle and needle.
Use the correct cleaning brushes and avoid metal wire that can enlarge precision air holes. Tighten components according to the supplier’s instructions; overtightening can damage sealing surfaces.
5. Excessive overspray
Overspray raises coating cost, increases booth-filter loading, and can create a dusty finish. Common causes include excessive atomizing pressure, a fan that is wider than the component, poor transfer angle, too much distance, or a mismatch between fluid output and operator speed.
Reduce pressure to the lowest stable setting, narrow the fan for small parts, keep the gun square to the surface, and plan the spray sequence to avoid repeatedly coating open air. The transfer efficiency of a LVLP SPRAY GUN depends on correct technique as much as the gun design.
6. Fisheyes and contamination
Fisheyes are small craters caused by surface contamination such as silicone, oil, wax, or water in the compressed-air system. Inspect cleaning products, lubricants, gloves, rags, hoses, filters, and nearby maintenance activities. Drain air lines and replace saturated filter elements.
Do not rely on additives as the first response. Removing the contamination source is safer and more repeatable than continually modifying the coating.
7. Build a defect-response routine
Stop and label the affected batch.
Record coating, viscosity, temperature, humidity, gun, nozzle, and pressure.
Inspect the pattern on test paper.
Check air cap, nozzle, needle, filters, and hose.
Change only one variable at a time.
Approve the correction on a sample panel before restarting full production.
By documenting causes and corrective actions, furniture factories can turn recurring defects into controlled process knowledge. This improves first-pass yield, stabilizes coating consumption, and gives procurement teams clearer criteria when evaluating future spray equipment.
