The Effect of UV Flexo Ink Viscosity, Anilox Cell Volume, and Press Speed on Print Density and Dot Gain

Tests were conducted with a 10-inch Comco Captain press on a polyester substrate to determine the effect of UV ink viscosity, anilox cell volume and line count, and press speed, on print quality and dot gain. Ink viscosity varied from 600 to 4,800 cps., press speed varied from 100 to 300 fpm, and cell volume varied from 1.5 to 8.0 BCM at 250, 400, and 700 lpi. Ink pigment concentration was constant, so that it was possible to make comparisons solely on the basis of ink viscosity. In general, print density decreased with increased ink viscosity, particularly for viscosities greater than 2,000 cps. A significant decrease in print density occurred when press speed was increased from 100 to 300 fpm. The decrease in density with speed was less for the 700 line anilox than the 400 or 250 line anilox rolls. Without exception, dot gain decreased as cell volume increased. Also, for a 70 percent screen, dot gain decreased as ink viscosity was increased from 600 to 2,000 cps. For the same cell volume, dot gain was less for the 700 line anilox than the 400 line anilox roll.