# Determining the Print Quality Due to Deformation of the Halftone Dots in Flexography
## 3 Methods  
The main goal of this research was to determine the print quality caused by the deformation of dots in flexography. To achieve the given goal, it was necessary to analyze the causes of certain types of deformations of dots on the printouts, determine the acceptability of the quality of the printouts thus obtained and find a solution to eliminate the problem. According to the characteristics of the flexographic printing process, it can be determined that there are many variable parameters that can disrupt the harmony of the dots and thus affect the visual impression of the reproduction. The research was based on the analysis of the imprints of two types of flexible labels in a roll, and the aim was to determine the most common dot deformations when printing this type of packaging. A Nilpeter FB4200 8-color flexo in-line printing machine with a max printing width of 450 mm was used for printing. Printing was performed using the principle \"from roll to roll\", with a printing speed of 120 m/min and UV ink applied. The optimal anilox line count for printing defined in cells per inch (cpi) or cells per centimeter (c/cm) was determined in line with the halftone screen and minimum dot size [26]. The anilox roller line count for the black color was smaller than for the other process colors. A smaller line count signified that a larger amount of ink could be transferred, which was determined by the volume of the anilox roller. This allows for a thicker ink film, which achieves a higher color density. This is especially important if higher coverage of a particular color in the print is required. The printing substrate is transparent, which means that the opaque white color is also used in printing. In order to achieve a higher opacity level of white color, an anilox roller of a larger volume and smaller line count is used [27]. Printing was performed on the back of a transparent printing substrate. Such printing is called reverse-side printing or back printing, and the order of colors in the print was reversed in relation to the printing on the front side, with the white color at the end. After printing, the graphic was legible on the front side of the printing substrate and not on the side of the printing substrate where the inks were printed. Table 1 shows the technical specifications of the entire printing process used in both experiments. \begin{table}
\begin{tabular}{l c} \hline \hline \multicolumn{3}{c}{**Plate-Making Process Specification**} \\ \hline Ctp device & Hell HelioFlex F1200 (LAMS technology) \\ Resolution & 2540 dpi \\ Photopolymer type & Flint nyloflex ACE, 62 shore A \\ Plate thickness & 1.14 mm \\ Base layer thickness & 0.125 mm \\ Line ruling & 133 lines per inch (lpi) \\ Screening type & Conventional AM, round dot shape \\ \hline \multicolumn{3}{c}{**Printing Specifications**} \\ \hline Flexo printing machine & Nilpeter FA-17 \\ Printing speed & 120 m/min \\ Process flexo inks & UV FoilStar LM yellow, magenta, cyan, black \\ White flexo ink & LightStar UV Opaque White Foil FCM ED405700 \\ UV curing & UV Lamp-Mercury Wavelength, 600 WPI output power \\ Printing width & 450 mm \\ Plate mounting tape & 3M E315, 0.38 mm thickness \\ Print run & 500,000 labels (experiment 1); 200,000 labels (experiment 2) \\ \hline \hline \multicolumn{3}{c}{**Anilox Roller Specifications**} \\ \hline Cyan & 440 c/cm (1020 cpi); 4.0 cm\({}^{3}\)/m\({}^{2}\) \\ Magenta & 440 c/cm (1020 cpi); 3.0 cm\({}^{3}\)/m\({}^{2}\) \\ Yellow & 440 c/cm (1020 cpi); 3.0 cm\({}^{3}\)/m\({}^{2}\) \\ Black & 340 c/cm (860 cpi); 5.7 cm\({}^{3}\)/m\({}^{2}\) \\ White & 120 c/cm (300 cpi); 8.6 cm\({}^{3}\)/m\({}^{2}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Technical specifications of the prepress and printing process. Many deformations of dots occur during the plate-making process [28] and the preparation of the printing machine. Some of them can be very easily spotted and effectively eliminated. However, when the dot deformation occurs during the printing process, often the error is not noticed in time.