An Experimental Study on the Pickout of Scaled-up Gravure Cells

Abstract

Abstract An experimental study was carried out to investigate the pickout of scaled-up gravure cells. The pickout of a gravure cell is defined as the fractional volume of the coating solution transferred from the cell to the moving roller. Gravure cells of different sizes and combinations were examined. Dilute poly(vinyl) alcohol solutions was used as test fluids. It was found that the stability of the liquid bridge that connects the moving roller and the gravure cell is the most critical factor to determine the pickout. The most stable condition that yields the maximum pickout is that the moving roller just touches the gravure cell and the coating gap is zero. Either a positive or a negative coating gap will decrease the pickout. The pickout for a small gravure cell is lower than a larger one because the liquid bridge is less stable. The experiment on different cell combinations reveals that if the number of gravure cells in the coating direction is increased, the average pickout per cell will drop. The pickout decreases as the capillary number increases. A universal correlation was found between the modified pickout and the capillary number. This modified pickout is the product of the pickout and a shift factor which involves all the geometric parameters in gravure cells.