Material Consumption and Dry Film Thickness in Spray Coating Process

Abstract

Material consumption and dry film thickness are the two main indicators for identifying the efficiency of spray coating process. Using a proper spray condition, less material consumption could be obtained as per a given dry film thickness. This paper presents the influences of supplying- air pressure, spray time and nozzle size of spray gun on the weight of material used per shot and the dry film thickness obtained. A high- volume-low-pressure type spray gun was used to atomize and deliver a liquid solution of Teflon depositing on a flat work surface. The experimental results showed that low spray time, large nozzle size and low spray pressure were responsible for the increased material consumption and dry film thickness. The optimization was performed, where the material consumption was minimized and the dry film thickness was set within a specified standard. Based on the geometric interaction between the spray gun and work-piece, a spray coating model in this application, which is considered unique was also developed and discussed in this paper. Moreover, this paper demonstrates a determination of the coefficient of spray coating process (k) through a relationship between coating thickness and material consumption using data obtained from the experiment. As a result, a relationship among the dry film thickness and positions of the spray gun was established and it can be used to predict the coating thickness. In conclusion, the optimal conditions in the spray coating process was determined to minimize material consumption whereas the developed spray coating model predicts the coating thickness related to the position of the spray gun. This model will substantially reduce spray gun setup time during production in order to obtain required dry film thickness.