# Determining the Print Quality Due to Deformation of the Halftone Dots in Flexography
## 5 Conclusions  
Through this research, the problem of dot deformation on concrete examples was presented. Experiment 1 involved the influence of a print run size on the dot deformation in the print. The measurements from experiment 1 showed that the dot coverages on the polymer plate were changing during the printing process, and these changes influenced the transfer of the ink on the substrate. The dot diameter was measured in five selected halftone areas in the midtones and light tones, and based on them, the coverage as a percentage was calculated. The measurement results showed that the changes in dot coverages in the midtones were linear throughout the entire print run, while in the light tones, they were more logarithmic. In the first fifth of the print run, the relative percentage deviation related to Stage I was 6.3% in the midtones and up to 52.6% in the light tones. In the remaining part of the print run, the percentage deviation in relation to Stage II was 17.5% in the midtones and up to 7.4% in the light tones. Therefore, significantly higher dot deformation appeared in the light tones (82%) in the first fifth of the print run in relation to the midtones (25%). An analysis of a graph of the ink density showed a much more homogeneous shape of the dot and greater dot sharpness at the beginning of the print run.  
The main problem with flexography is the loss of tones on the print in the highlight and shadow areas. While the loss of tones in shadows results in a reduced print contrast, the loss of tones in highlights results in a sudden interruption of the tones below the minimum printable dot value (cut-off tones effect). Deformations are much more noticeable on flat tones and gradients in relation to colorful visuals and images. The goal of every packaging manufacturer is to eliminate such anomalies or at least to minimize them. By analyzing the topographic view of the dots from experiment 2, it can be concluded that it is important to determine and maintain the minimum size of the dot and choose the right anilox line count accordingly. The smallest dot on the printing plate must be larger than the cell of the anilox roller. Based on the analysis of the results, in accordance with the sizes of the minimum dot, the optimal ratio of the anilox line screen and plate line screen was defined and amounted to 5:1 for 3%, 6:1 for 2% and 8:5:1 for 1% dot coverages.  
When processing an image for flexography, it is often necessary to compromise on the method of prepress for 1% coverage. Inadequate specification of the printing process for 1% coverage can make a dirty print that looks much darker than that at 2% coverage. This is the most common problem with the black channel. Therefore, a \"bump-up\" curve is applied in prepress, which ensures a minimum dot on the printing plate and also in printing. In practice, the 2% coverage is often set as the minimum dot, thus significantly reducing the requirements for a high line count int the anilox roller while still keeping the plate line screen unchanged.  
These results are of great interest for graphic reproduction, as they provide insight into the stability and endurance of the polymer plates during the printing process, as well as defining the size of the print run with the optimal print quality.  
Data curation, D.V.; Investigation, L.V.; Methodology, K.H.; Visualization, R.G. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The authors declare no conflict of interest.