Changes in Thickness and Gloss of Dry Films According to Spray Methods of Water-Soluble Metallic Base Coat

—The distance between the object and the spray gun and the degree of coating overlap due to the spray distance must be optimized for achieving a uniform coating using a spray gun. Moreover, the paint sprayed from a spray gun is thicker at the center of the object to be painted and thinner toward the edges due to the difference in density. Therefore, the thickness of the paint according to the spray distance should be considered. In this study, a Three-Dimensional (3D) painting robot specially designed to spray paint under certain conditions was used to investigate the spray characteristics of the spray gun and the thickness and glossiness of dry films according to the spray distance and moving speed. Under the standard coating conditions for automotive refinishing, the optimum distance between the object to be coated and the spray gun is approximately 12–15 cm, and the speed of the spray gun is about 0.4–0.5 m/s. If the spray distance is small, the coating film will be thick, and the resin ratio will be high, with metallic particles embedded in the resin, resulting in low glossiness. The metallic particles are exposed on the coated surface at a larger distance, increasing the glossiness.