The coating process involves applying a thin material layer to a surface to engender it with specific desirable properties or enhance its performance. In the production of print media (labels, packaging, printed textiles, and promotional materials), the standard functions of the coating process include visual decoration, which involves the addition of appealing colors, textures, and patterns. A pertinent issue in the printing industry is that at present, the predominant coating process uses printing and coating technologies (gravure, flexo, letterset, letterpress, screen printing, inkjet, and electrophotography) and lamination (i.e., attaching decorative layers of materials, such as films or fabrics). In this paper, we present a new method for testing the efficiency with which different-sized metalized printing elements (using gold foil) may be applied to paper substrates; to do so, we gradually vary the amount UV-cured inkjet varnish (or adhesive) that is applied. To test the effectiveness of this method in producing metallic visual effects, we utilize seven different thicknesses of UV-cured varnish with the aid of modular piezo inkjet heads (KM1024 iLHE-30) and three different printing speeds. Our research shows that to achieve optimal production of cold metalized foil, a 21 µm layer should be deposited, and the substrate should move at a speed of 0.30 m/s.

The new European Regulation (EU) 2025/40 includes provisions on modern packaging and packaging waste. It defines the use of image QR codes on packaging (items 71 and 161) and in personal documents, making line barcodes a thing of the past. The definition of a QR code is precisely specified in ISO/IEC 18004:2024. However, their implementation in printing systems is not specified and remains an important factor for their future application. Digital foil printing is a completely new hybrid printing process for applying information to highly precise applications such as QR codes, security printing, and packaging printing. The technique is characterized by a combination of two printing techniques: drop-on-demand UV inkjet followed by thermal transfer of black foil. Using a matte-coated printing substrate (Garda Matt, 300 g/m²), Konica Minolta KM1024 LHE Inkjet head settings, and a transfer temperature of 100 °C, the size of the square printing elements in QR codes plays a decisive role in the quality of the decoded information. The aim of this work is to investigate the possibility of realizing the basic elements of the QR code image (the profile of square elements and the success of realizing a precisely defined surface) with a variation in the thickness of the UV varnish coating (7, 14 and 21 µm), realized using the MGI JETvarnish 3DS digital machine. The most commonly used rectangular elements with a surface area of 0.01 cm² were tested: 0.06 cm², 0.25 cm², 1 cm², 4 cm², and 16 cm². The results showed that the imprint quality is uneven for the smallest elements (square elements with base lengths of 0.1 cm and 0.25 cm). The effect is especially visible with a minimum UV varnish application of 7 μm (1 drop). By increasing the amount of UV varnish and the application thickness to 14 μm (2 drops) and 21 μm (3 drops), respectively, a significantly more stable, even reproduction of the achromatic image is achieved. The highest technical precision was achieved with a UV varnish thickness of 21 μm.

The major objective of this paper consists in acquiring new knowledge and understanding the interaction between the printed metalized foil and the paper printing substrate. Since the Inkjet printing principle is often used for the adhesion of metalized foils (cold-hot process), it is necessary to investigate the influence of piezo Inkjet head settings on the final imprint. The light distribution on the halftoned metalized print depends on the optical properties of the paper and the metalized foil. Therefore, the problem of accurate reproduction is divided into the distribution of light in the paper and the reflection from the printed round metalized printing elements. For ImageJ software (gold dot imprint photographs), two physical quantities were analyzed (realized edge parts and anisotropic scattering of light from the printed surface = dot gain), which ultimately achieved a change in the realized dimension of print elements. In this paper, the authors present a new method for testing the efficiency of halftones (50% TV surface coverage) created with four diameters of gold foil printing dots (0.100 mm; 0.250 mm; 0.500 mm; 0.750 mm) applied to matte fine art cardboard. The experiment involved a gradual variation of the amount of UV-cured Inkjet varnish used, which played a crucial role in the production of metallic visual dot samples. To assess the effectiveness of this method, three different thicknesses of UV-cured varnish (29 µm, 43 µm, and 58 µm) were used in conjunction with modular Konica Minolta Jetvarnish 3DS machine (piezo Inkjet heads KM1024 iLHE-30), and constant printing speeds of 0.30 m/s. The research findings indicate that a 29 µm layer thickness of UV varnish and the substrate moving in cross-direction are optimal for producing cold metalized foil lines. However, the results also show that a more significant application of varnish offers a better chance of reproducing the dot and achieving a better contrast. The results show that elements smaller than 0.250 mm cannot be realized and that the print optimum will be achieved with UV Inkjet varnish application settings greater than 29 µm and less than 43 µm.

The origin of dot gain comes from two primary contributions: optical and mechanical, and therefore two functions describing these contributions have been tested. These contributions are reflected in the asymmetric shape of the Line Spread Function (LSF), which is a critical parameter for analyzing the quality of printed images. This paper uses a robust iterative method to fit LSF curves, incorporating multiple single peak functions to increase measurement accuracy and enhance understanding of the phenomenon. High correlation results demonstrate the plausibility of separating these contributions and determining their percentage share within the profile. Optical dot gain, modeled using a Lorentzian function, accurately reflects its dependence on substrate properties. Mechanical dot gain, on the other hand, is described by a Gaussian function, capturing its link to printing techniques. The high correlation (R > 0.97) between experimental and modeled data validates the robustness of this method, enabling precise determination of the percentage share of each component. The results indicate that optical dot gain contributes approximately 30 % of the total, a much larger share than previously assumed. This highlights the importance of substrate selection and treatment in achieving print quality. In the context of electrostatic printing, a third, previously undetected contribution was identified. Although minor, this additional mechanical component (Gauss1) is reproducible and directly linked to the operational state of the printing machine, adding complexity to the dot gain phenomenon.

Lattice structures are extremely useful geometric structures that can exhibit a broad range of desired mechanical properties, allowing them to be tailor-made for specific purposes. However, manufacturing of such structures using traditional methods is difficult or even impossible. 3D printing technologies enable vastly easier production of such structures, allowing for easy and fast production of mechanically tuneable materials. While such structures can have any density, low-density variants provide certain properties that can be desirable in a broad spectrum of applications. This paper explores the tuning and production of one such type of lattice structure using desktop FDM 3D printers, with a special emphasis on lowest possible density that can be achieved. Lattice structures are derived from modified selected parametric infill patterns available in the slicer software. Structures are produced using Acrylonitrile Styrene Acrylate with optimised manufacturing parameters that allow for low-density lattice production.