Papers by Keyword: Offset Printing

Abstract: The quality and chemical composition of water have a significant impact on the stability and efficiency of printing processes. Water is the basis of dampening solutions, used for washing blankets in offset printing and for cooling equipment. Ordinary tap water has an unstable composition, in most cases a high total hardness value, and contains calcium, magnesium and iron salts. The use of such water is unacceptable, as it can lead to printing technology malfunctions and cause defects in printed copies. It has been established that in order to ensure stable print quality, it is advisable to implement a multi-stage water treatment system for printing production. The proposed system includes mechanical filtration using titanium membranes to remove solid particles, softening and desalination of water using complex action columns or reverse osmosis technology, and disinfection to eliminate biological contamination. To restore the technologically necessary level of total mineralisation of water, the hardness is increased again. The paper calculates the required volumes of purified water used in offset printing depending on the volume of printed products. This allows the necessary productivity of filtration and softening units to be estimated. The paper calculates the required volumes of purified water used in offset printing depending on the volume of printed products. This allows assessing the required performance of filtration and softening units, as well as determining the feasibility of using closed or partially closed water circulation systems.

Abstract: This article explores treatment method of waste fountain solution from sheet-fed offset printing. First calcium chlorate is used to have a oxidation treatment for the waste water, then it is dealt with composite coagulants polyaluminium chloride (PAC) and cation polyacrylamide (CPAM) under different pH value. The results show that quality of the waste fountain solution could reach the national second-grade standard of sewage comprehensive discharge through the above treatment (GB 8978--1996) when treating with 0.7 g/L calcium hypochlorite and then sinking with PAC 4.0 g/L, CPAM 75.0 mg/L under the pH value of 8.0 for about 10 minutes. With the optimum treatment conditions removal rates of COD, ammonia nitrogen, phosphate and hexavalent chromium are above 90%, 94%, near to 98% and above 99% respectively.

Abstract: In order to improve the printing quality and know the process of ink transferring well, ink flowing among ink rollers is simulated by using CFX. Firstly ink transferring characteristics between two rollers are analyzed. An experiment is carried out to test the accuracy of this simulation analysis. Then ink transferring characteristics among three and five rollers are analyzed respectively. The general characteristics of ink transferring among rollers are got by comparing the velocity of ink flowing, ink pressure and ink transfer ratio from those simulations. What is more, the accuracy of the simulation analysis is verified by experiment. And this research provides a reference to general characteristics of ink transferring in the actual printing process, and its important for the printing color quality control and has a better application prospect.

Abstract: In order to control digitally the print-through, the print-through criterion of offset printing was studied in this article. For 4 given paper samples, the paper properties including paper opacity and K&N ink absorbency were tested, and then print-through value expressed with ΔD and ΔE_ab^* was measured under 9 sets of printing condition. The results showed that lower printing press and higher printing speed were helpful to reduce the print-through. And under the same printing conditions, the print-through value of cyan ink print was slightly larger than that of magenta ink print. In addition, the print-through values of offset paper samples were a bit larger than that of newsprint samples. In particular, no matter what kind of conditions were, the print-through value expressed with ΔD and ΔE_ab^* were lower than 0.04 and 4NBS when the PTR value was larger than 72%. The criterion of print-through was firstly given, which was very helpful to choose paper during the offset printing.

Abstract: The principle of offset printing is the graphic part lipophilicity and the blank part oleophobic hydrophilic. Based on the ink-water balance theory, this paper mainly discusses the base paper and the coating formulations of paper-based printing plate. In this paper the properties of the paper-based printing plate of the different coating formulations were detected and evaluated, meanwhile these plates were tested in the offset printing. Based on the detection of print quality, plate coating performance and the number of copies printed, the base paper and coating formulations of this plate was be determined. The results of this study for this plate have some significance in the actual production.

Abstract: Rich mineral paper (RMP) has the advantage of being energy efficient, clean and creating no pollution during its production processes, with low production costs, and enjoying naturally complete biodegradability, fully compatible with the emerging demands for energy efficient carbon reducing features and the trend for environmentally green solutions, so if this media can replace traditional paper uses to become a new print media, tremendous environmental efficacy can be expected. So this study aims to discuss the print quality performance characteristics of RMP applications in large print run offset printing operations. The study deploys True Experimental Study methodology, with use of the digital printing test target of Graphic Arts Technical Foundation (GATF), with flat offset printing on traditional coated paper and eco-friendly RMP, printing 800 sheets of each, with systematic random sampling of 35 samples for the study. Quality determinations rely on X-rite i1 Pro for elucidation of the printing quality characteristics for solid ink density, TVI, contrast, gray balance, and color gamut measurement. The results of this study indicate the KCMY solid ink density and contrast of the eco-friendly RMP were less than traditional coated paper; TVI value was higher than traditional coated paper; color gamut performance was less than the traditional coated paper. Optimal gray balance combination for RMP was determined as follows: 7% tone with C7M3Y4, 30% tone with C30M28Y26, 60% tone with C60M58Y5, and 80% tone with C80M76Y66. The study suggests that ink particularly suitable for RMP uses remains in need of development. Additionally, the study found that use of RMP in the paper machinery indicated transverse and longitudinal tensile strength is slightly inferior to the traditional coated paper, resulting in unsmooth surfaces post-printing, for which it is recommended that RMP makers should consider paper machinery structural aspects when pursuing future research on modifying solutions for greater printing efficacy with RMP.

Abstract: Paper based printing plate is one of printing plates used in eight mo octave or specifically offset printing machine. In the printing process, the printed plate wants to keep its shape by the pressure, the friction and tension. It needs to have good dimensional stability and good ink-water balance of coating. This paper discusses the influence of different coating formulations and coating process on the mechanical properties of paper-based printing plate. In this paper, the wet strength of paper-based printing plate of different formulations and different coating amount were tested. The study provided the theoretical basis for ink-water balance coating formulations of paper-based printing plate and the plate production.

Abstract: In order to improve the quality of colorful offset printing and know the process of ink transferring, this paper adopts the method of theoretical analysis and experiment, the velocity and pressure of the ink flow field are analyzed when the rubber roller deforms and the two rollers rotate, and the effective ink layer thickness is extracted, then the ink transferring rate can be got. The rubber roller’s deformation and ink transferring rate under different conditions are got, and factors, such as rotation velocity, deformation of rubber roller, ink layer thickness between two rollers, which affect the ink flow and transferring rate are analyzed.

Abstract: In order to control digitally the print-through, the print-through standard of offset printing was studied in this article. For 4 given paper samples, the paper properties including paper opacity and K&N ink absorbency were tested, and then print-through value expressed with ΔD and ΔEab* was measured under 9 sets of printing condition. The results showed that lower printing press and higher printing speed were helpful to reduce the print-through. And under the same printing conditions, the print-through value of cyan ink print was slightly larger than that of magenta ink print. In addition, the print-through values of offset paper samples were a bit larger than that of newsprint samples. In particular, no matter what kind of conditions were, the print-through value expressed with ΔD and ΔEab* were lower than 0.04 and 4NBS when the PTR value was larger than 72%. The standard of print-through was firstly given, which was very helpful to choose paper during the offset printing.

Abstract: This paper analyzes the defect of some methods for controlling the ink key of offset printing machine, and presents the advantage of adaptive fuzzy control. Aiming at the problem that the processing curve of offset printing is changed by the environmental impact of production, this paper analyzes this non-real-time measurement and control system with time delay and less test data, and proposes the method of adaptive fuzzy control to amend the control table and adjust the slope of the control curve according to the detection deviations. Finally, the control rules are adjusted to meet the actual situation. By simulating the control arithmetic with the example of the control of printing ink keys under specific conditions using Matlab / Simulink, it is proved to be effective to achieve the expectative effect.