Optimization of flexo process parameters to reduce the overall manufacturing cost

The flexo process parameters play an important role in ink transfer and will lead to wastage of inks, substrate, solvents and printed stocks if not monitored and controlled. The work focuses on optimizing the flexo process parameters for 40 microns 3-layer polyethylene (PE) film with Blue Nitrocellulose (NC) ink to reduce overall manufacturing cost while maintaining the print quality for diaper application. An experimental design was conducted for the response Ink GSM (grams per square meter), ?E and Print Mottle with factors such as ink viscosity, anilox volume, plate dot shape and substrate opacity. The data was analyzed through Main Effect, Interaction Plot and Analysis of Variance (ANOVA). The regression models were developed for the response to validate the predictive ability of model. The process optimization resulted in reduction of Ink GSM, ?E and Print Mottle by 18%, 52% and 1% respectively. The ink consumption reduced by 18.26% with minimized print defects, thereby reducing the overall manufacturing cost.

The effect of paper coatings containing biopolymer binder and different natural pigments on printability

Paper is an environmentally friendly, recyclable material whose main material is cellulose, which can be obtained from all kinds of trees and plants, used as writing, printing and packaging material. Due to its structural properties, papers are not resistant to temperature and humidity, as well as problems with ink transfer with its porous structure and experienced negative printability properties. In recent years, especially the growth of the packaging industry has increased the demand for papers with improved printability properties. In order to obtain better printability properties from papers, some processes can be performed in paper production, as well as some surface treatments after production. These processes are paper coating, sizing and calendering. Paper coatings are generally water-dispersed coating solutions with one or more pigments, binders and certain additives to improve the desired properties. With these processes, by filling the gaps between the pores of the paper, a shapely and smooth surface is obtained and good printability is obtained together with the optical and physical properties of the papers. In this study, the interactions and printability properties of different types of pigments with xanthan gum binder were investigated by preparing paper coating formulations using calcium carbonate, barite and talc pigments and xanthan gum as binder. As a result, xanthan is a good coating binder and CaCO 3 {\mathrm{CaCO}_{3}} from the compared pigments is the most suitable compared to the other 2 pigments, considering all the studied areas.

Effect of Temperature on the Ink Transfer of sublimation Printing Process

The effect of temperature on the ink transfer of sublimation printing technology was investigated. The ink transfer was conducted by the colour density of single solid inks and the ink trapping of overprinted solid inks. The experimental results indicate that the amount of ink transferred from the colour ribbon to the substrate is determined by the thermal characterization of dye materials. The densities of single colour inks as well as the ink trapping coefficients obtain the highest values at the temperature corresponding to the endothermic peaks of the dye materials. This is the optimum operating processing temperature.

One-step photonic curing of screen-printed conductive Ni flake electrodes for use in flexible electronics

Photonic curing has shown great promise in maintaining the integrity of flexible thin polymer substrates without structural degradation due to shrinkage, charring or decomposition during the sintering of printed functional ink films in milliseconds at high temperatures. In this paper, single-step photonic curing of screen-printed nickel (Ni) electrodes is reported for sensor, interconnector and printed electronics applications. Solid bleached sulphate paperboard (SBS) and polyethylene terephthalate polymer (PET) substrates are employed to investigate the electrical performance, ink transfer and ink spreading that directly affect the fabrication of homogeneous ink films. Ni flake ink is selected, particularly since its effects on sintering and rheology have not yet been examined. The viscosity of Ni flake ink yields shear-thinning behavior that is distinct from that of screen printing. The porous SBS substrate is allowed approximately 20% less ink usage. With one-step photonic curing, the electrodes on SBS and PET exhibited electrical performances of a minimum of 4 Ω/sq and 16 Ω/sq, respectively, at a pulse length of 1.6 ms, which is comparable to conventional thermal heating at 130 °C for 5 min. The results emphasize the suitability of Ni flake ink to fabricate electronic devices on flexible substrates by photonic curing.

Anilox Cell Geometries For Printable Electronics and Flexible Packaging

Flexography is a major high-volume printing process used extensively for flexible packaging. The heart of flexographic press is the anilox roll, which meters the flow of ink to the image carrier (plate) by virtue of the engraved cells on the surface. The anilox was original engraved mechanically using a stylus to peck at the surface. This limited the size and profile of the engraved cells. However, laser engraving has enabled much more control with a variety of shapes and aspect ratios. Much has been claimed by the manufacturers for these new designs – improved ink transfer, higher volumes of ink transfer and better half tone reproduction – on the basis of industrial field trials. The objective of the research reported in this thesis has been to quantify the ink release from the anilox to the plate for both traditional cell profiles and the open channel designs.Previously, the ink release was mostly determined by examining the optical density of the print products. The optical density is a qualitative indicator of the ink release from anilox cells. These studies were limited to closed anilox cells with a low ink viscosity, as typically used for graphic prints. This study explores an extended range of anilox cell shapes, including open channel geometries, and the ink viscosities. The ink released from the anilox cells has been be directly measuring and quantified.Experiments were performed printing directly to glass and on flexible packaging at a commercial printers to establish the current industry position. A laboratory scale printability tester was then used to study ink release using three inks: UV Cyan, Carbon and Silver. These represented a link to the graphic experiments in previous published studies, while the Carbon and Silver were highly viscoelastic functional inks used in printed electronics. Four cell geometries were used: laser engraved closed cells, extended hexagonal and wavy channels together with mechanically engraved conventional closed pyramid cells. The laser engraved anilox afforded the opportunity to vary key parameters of cell width, depth, profile and volume. A brief exploration of print speed was also undertaken with exemplar anilox of each cell type. The main study considered ink transfer to a 100% solid plate, as this would allow the ink release to be studied without influence of the plate distorting into the cells thereby extracting more ink. A limited study was then undertaken with a half tone plate to establish the impacted on ink transfer.The amount of ink transferred was highly dependent on the absolute volume of cells, i.e. the amount of ink available on the anilox. The anilox cells with wider, shallower and smaller depth-to-width ratio released a higher proportion of the ink. The ink’s physical characteristics of viscoelasticity and extensional viscosity also determine the proportion of ink transferred.The anilox hexagonal closed cells (typically used in the flexographic printing process) performed best with the low viscosity ink. The information gaining from this study would aid in the design of anilox cell geometries and development of ink characteristics to enhance its capability for functional print applications such as printable electronics. The anilox wavy channels released the greatest proportion of the ink with high viscosity, elastic modulus, and filament breakup time. The anilox wavy channel has the potential to be used for the functional print as it increased the release of paste-like ink. Additionally, it improved the ink lay-down. The anilox engraving technique affected the ink release. The anilox cells, which were engraved by the laser technique, gave greater ink release comparing to the anilox cells, which were engraved by the mechanically engraving technique. The increase of the dot coverage increased the ink release out of the anilox cells because of the increase of the receiving area. However, the increase of the ink release plateaued after the dot coverage of 50% for UV Silver because of its large filament breakup time.The characteristics of ink influenced the ink release out of the anilox cells. Unlike previous work which examined only the ink viscosity, this studied included ink elastic modulus and filament breakup. The ink with high viscosity and elastic modulus, but small filament breakup time gave greatest ink release for all anilox shapes.When the printing speed increased, it decreased the ink release due to two factors; reduction of engagement time between the anilox cells and the plate (reducing time for ink to transfer) and enlargement of the filament extension rate (reducing the amount of ink transfer). The decrease of ink release was affected by the ink characteristics and the anilox cells shapes. The decrease of ink release was significant when UV Cyan ink (small viscosity and elastic modulus) was used with the anilox open cells and wavy channels. Contrarily, the decrease of ink release was insignificant when UV Carbon and Silver inks (large viscosity and elastic modulus) was used with the anilox open cells and wavy channels.The experimental data was analysed and the critical parameters in releasing the ink of the anilox cells were identified. The depth of anilox cell was the most critical parameter; the shallower cell depth released a higher proportion of the ink. The ratio of depth-to-width was the second most important parameter in determining the ink release. The smaller depth-to-width ratio released more ink. The width of anilox cell could not be used as a parameter predicting the ink release because the wider anilox cell did not always release the higher proportion of the ink.

Investigation of anilox roller cell clogging

One vital component in the flexo inking system of high-line screen engrav-ing technologies is anilox rollers. These deliver a precise and consistent amount of ink during the process of flexography, making it possible to produce high-resolution prints of exceptional quality. However, as print quality continues to improve, printing houses are experiencing more fre-quent problems with anilox rollers, such that ink transfer during printing operations is being unpredictably reduced. Due to the lack of research into anilox rollers there is insufficient objective information on how to maintain them at peak performance and condition. This study investigates the clogging of anilox roller cells (without assessing cell wear) in a num-ber of printing houses in the Baltic States. Cell clogging of anilox rollers was determined depending on cell size, ink type and washing method.

Investigation of Roll-to-Roll Gravure Printing for Printed Electronics with Fine Features

Gravure printing is known to be cost competitive in manufacturing of printed electronic devices due to its capability to mass produce at lower costs. Current standard of gravure printed feature sizes is in a range of around 50 μm down to sub-10 μm, predominantly through small scale setups and specialized engraving. However, reliance on gravure cell design limits the scalability of printing over a large area due to the setup cost. In this study, ink viscoelastic behavior was modified to improve replication of gravure printed features over a large printing area of 300 mm web-width without a reduction in gravure cell dimension. Fine lines were printed using a high viscosity ink with a good replication of the nominal line width. Control over the printed features was performed through the variation of printing speed and the alteration of ink viscosity. The effects of ink viscosity and printing speed on the printed ink particle distribution and size were also examined. New methodologies of characterizing ink transfer were also developed to help understand the ink transfer processes: mass transfer and particle transfer. A deeper understanding of the thixotropic effect and shear recovery behavior of inks was achieved through simulations of shearing conditions.

Predicting Ink Transfer Rate of 3D Additive Printing Using EGBO Optimized Least Squares Support Vector Machine Model

Ink transfer rate (ITR) is a reference index to measure the quality of 3D additive printing. In this study, an ink transfer rate prediction model is proposed by applying the least squares support vector machine (LSSVM). In addition, enhanced garden balsam optimization (EGBO) is used for selection and optimization of hyperparameters that are embedded in the LSSVM model. 102 sets of experimental sample data have been collected from the production line to train and test the hybrid prediction model. Experimental results show that the coefficient of determination (R2) for the introduced model is equal to 0.8476, the root-mean-square error (RMSE) is 6.6 × 10 (−3), and the mean absolute percentage error (MAPE) is 1.6502 × 10 (−3) for the ink transfer rate of 3D additive printing.