Improvement of the Transfer Efficiency of the Atomized Powder Coating System by Increasing the Conveying Air Speed

This paper deals with improvement of the transfer efficiency of powder coating by increasing the conveying air speed using the atomized powder coating (APC) system. In addition, the details of the powder-mass-flow-rate sensor, which forms the basis of the APC system and realizes sensor-based full automatic control of the system, are described. Usually, for most of the conventional powder coating systems, the conveying air of approximately 80 L/min has been recommended as the empirical standard to avoid decreasing the transfer efficiency and to specifically prevent blowing off a part of the powders deposited on the object. By contrast, for the APC system, the coating thickness in the recessed area was clearly increased with the increase of the volume of the conveying air. Thus, the increase of the volume of the conveying air from 80 to 120 L/min has yielded a 13% increase in the average coating thickness. Such an increase in the coating thickness can be ascribed to the increase of charge density on the powder particles sprayed from the gun.