There are many factors that affect electrostatic powder coating, such as: equipment factors, operating factors, etc.. But the main factors are powder conductivity, powder particle size, spraying voltage, spraying distance (between the gun and the workpiece), air supply pressure, etc.
1, powder conductivity: the volume of powder particles must be moderate, volume resistance is too large, the powder charge is not easy to release, the workpiece surface charge gathered too much, the repulsive force is not thick film. Volume resistance is too small, charged powder is easy to release charge, attached powder is easy to fall off. So the volume resistance of the powder is generally in the range of 1010-1014Ω.cm the most appropriate.
2, powder particle size: particle size affects powder mobility, coating, and the gun blockage and film thickness, etc.. Particle size is too small, the charge is small, electrostatic gravitational force is small, the coating particles are easy to be thrown off, on the powder rate is low. The particle size is too large, self-reliance, charged, the repulsive force between the paint particles is also large, the powder rate is reduced.
3, spraying voltage: spraying voltage and electrostatic gravitational force is proportional to the general low voltage, with the voltage increases, the powder charged amount increases, the amount of adhesion increases, but reaches the saturation value, will produce electrostatic repulsion, play the opposite role, because the voltage is too high, will make the powder breakdown. General voltage control at 60-80KV.
4, spraying distance (gun and workpiece): the size of the spraying distance affects the size of the electric field strength. General spraying distance control in 200-300mm, powder deposition efficiency is the best, when the distance is too small, easy to produce a fire, the powder breakdown, affecting the quality. When the distance is too large, the powder deposition efficiency is too low, increasing the recovery of powder, so that the powder is contaminated with more opportunities.
5, air supply pressure: when spraying try to keep the air pressure and powder delivery air volume in the required minimum required amount, air supply pressure, powder kinetic energy increases, easy to cause the powder to rebound on the surface of the workpiece, so that the powder deposition rate decreases, therefore, the air supply pressure including - for powder air pressure, atomization air pressure, fluidization air pressure, the three pressures will affect the spraying efficiency and coating quality. Spray gun classification:
two kinds of corona type spray gun and friction gun
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