Optimization of Powder Spray Process Parameters using Taguchi Methodology

Powder coating of metal product is essential to avoid corrosion and to improve surface properties. The coating thickness alone doesn't ensure the corrosion resistance. If surface is not covered completely, the microgaps can initiate rusting. Hence, microstructures should be observed for various coating thicknesses. This study aims to study the effect of powder coating parameters (gun stand-off distance and gun traverse speed) on coating thickness and microstructure. First, the range of process parameters in which desired values of coating thickness is found and then second experiment is carried out to optimize the powder spray process parameters. The experimental investigation is done using DoE, Taguchi design, L-16 orthogonal array. Obtained experimental results were analyzed using Minitab 16, statistical software, to study the effect of process parameters on response variables. To understand the effect of process parameters, the main effects, interaction and contour plots are obtained. The ANOVA results were studied to understand significance of process parameters on coating thickness. The results also show that F-value for gun stand-off distance is much higher than that of gun traverse speed. Hence, the gun stand-off distance is major parameter affecting coating thickness. The microstructure studies were carried out to see uncoated gaps for various combinations of process parameters. Powder coating at very close distance and at low gun speeds results in excess coating thickness and uneven surface structure. The second experiment was conducted to optimize process parameters.