The article considers the rheological characteristics of printing inks and substantiates the need to measure the ink viscosity in a wide range for the high-quality printed products manufactured. It carries out the analysis of viscosimetry methods for researching of the ink rheological properties used in the printing industry. The structures and the operation principle of the most used viscometers for determining the printing inks viscosity of different printing methods are considered. The structural features of cup viscometers used following international standards are analyzed. The dependence of kinematic viscosity on the time of fluid leakage is studied for standard viscometers models that are built based on empirical equations for calculating the conditional viscosity. The reasons for significant differences in measuring time values for cups with different geometries and nozzle diameters at the same ink viscosity are indicated.
The rotational method of measuring viscosity is considered. It is determined that rotary viscometers with coaxial measuring systems are used for liquid flexographic and gravure printing inks, and rotary viscometers with cone-plate measuring systems are provided for inks with high viscosity of offset printing method. Based on the presented mathematical formulas for determining the torque of a moving element, a simulation model of a rotary viscometer in Matlab-Simulink is constructed, which reproduces the relationship between the geometric parameters of a moving element and viscosity. According to the modeling results and two-factor analysis, the conditions of using the shafts and cones by their geometric dimensions are determined.
Keywords: printing inks, viscosity, cup viscometer, rotary viscometer, coaxial cylinders, cone-plate, simulation model.
doi: 10.32403/0554-4866-2022-1-83-21-35
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