Виявлення впливу швидкості флексографічного друку на появу підстрибуючого ефекту (bouncing effect) на відбитках

The paper studies the influence of flexographic printing speed on the manifestation of the bouncing effect and imprint quality indicators. Printing was carried out on an Optima 2 flexographic machine (Soma Engineering, Czech Republic) on a white polypropylene film with a thickness of 20 μm. The study was carried out using a test printing form containing solid fills, raster areas (25%, 50%, 75%), linear elements and gradients. The geometric parameters of the lines were analyzed using an electron microscope. Spectrodensitometric studies of optical density and dot gain (TVI) in three zones across the width of the web were also conducted. The appearance of vibration defects in the form of banding and doubling of elements was observed at printing speeds of more than 400 m/min. It was found that with an increase in printing speed from 100 to 600 m/min, the TVI value decreases on average by 15–25% depending on the tone. Based on the results obtained, second-order regression models were constructed that describe the dependence of TVI on printing speed and position on the web. Based on these models, the corresponding response surfaces were synthesized and analyzed. For a tone of 75%, a pronounced nonlinear nature of the process is observed (R2 = 0.93), for 50% – moderate nonlinearity (R2 = 0.88), for 25% – almost linear dependence (R2 = 0.81). The adequacy of the models was confirmed by the Fisher criterion, and the homogeneity of the experimental data – by the Cochran criterion. It was found that the position on the web is a significant factor determining the distribution of TVI, which indicates the spatial heterogeneity of the printing process. The results obtained can be used to optimize high-speed flexographic printing modes and reduce vibration defects during the manufacture of packaging products