In recent years, flexo printing has also developed rapidly in China, but overall, China's flexo printing technology is still in its infancy. In the total printing volume, flexo printing products accounted for only about 1.5%, and mainly used for printing paper boxes and corrugated boxes. Flexo printing has not yet been applied in the newspaper printing industry in China.
Problems with Offset Printing
The basic requirements for newspaper printing are: first, to be time-efficient, to provide newspapers for the majority of readers at the fastest speed; second, to meet quality requirements, to have clear graphics, bright colors, and good visual effects; and third, to be economical, Under the premise of meeting basic requirements, minimizing costs should be minimized. The fourth should be environmental protection. Under the condition that the international community is increasingly demanding environmental protection, the basic conditions for meeting the requirements of environmental protection should be printed. Below, we will make a brief analysis of offset printing and talk about offset printing.
1. Adjust the structure of newspaper printing
At present, in the printing of newspapers in our country, it is almost the world of offset printing. Regardless of the size and amount of printing, all use offset printing. While Europe and North America broke the single pattern of offset printing in the 1990s, we should also rationally choose the printing method based on specific circumstances. For example, the cost of offset printing for newspapers with tens of thousands of copies will increase significantly. At this time, different printing methods can be selected according to different requirements.
2. Excessive paper loss rate and scrap rate is a prominent problem in offset printing
In offset printing, controlling the ink-water balance is an important issue, and achieving a water-ink balance in offset printing requires a process. Under normal circumstances, it takes about 15-30 minutes to adjust and test the printing stage from the time of starting up to enter a stable working state, which will inevitably increase the loss rate. In the offset printing process, there are many factors that affect the ink-water balance, and most of these factors are changed. Even under normal printing conditions, waste products may appear due to changes in certain conditions. For example, the loss rate of sheet-fed four-color offset presses is generally as high as 7%-15%, and the loss rate of web offset printers is even higher than that of sheetfed offset presses. Therefore, from the economic point of view, offset printing is not the best.
3. Offset printing does not have much advantage in printing quality
Offset printing is of higher quality and is based on many conditions. If the surface properties of the printing materials are high, fine prints can only be printed when higher-quality, higher-quality coated paper is used. Printing on newsprint is prone to the following problems: (1) offset printing uses fountain solution, and newsprint paper is highly water-absorptive, and the whiteness of the paper will decrease after absorbing water; (2) the surface roughness of the newsprint will affect the clarity of the text. (3) In the printing process, it is easily affected by external factors, and the printing quality is poor in stability. It is prone to defects such as uneven ink and dull colors.
4. Offset printing is at a disadvantage in environmental protection
Offset rotary printing inks are low viscosity solvent inks. The solvent content of the ink is high. Without the oxidation of the conjunctiva catalyst, it is directly absorbed by evaporation and evaporated by heating. It is difficult for the prints to be fully dried within a few hours, not only in the printing process. Dirty troubles occur, and when the reader gets the newspaper, the ink will still stick to his hands. In addition, solvent-based inks have a strong odor, which is detrimental to both the operator and the reader. In addition, volatile organic solvents in the ink are contaminated by the environment. Therefore, rotary offset printing ink is a contaminating ink and its use should be gradually restricted.
5. Offset printing has certain requirements for paper
Offset printing has a higher printing speed and uses fountain solution. If the paper is too thin, it may cause breaks. Therefore, the paper used for offset printing should not be too thin, and should not be less than 52 g/m2 in general, which will also increase the cost of printing products.
6. Offset has higher requirements on the technical level of operators
Because the structure of the offset press is relatively complex, the adjustment position is the most among various types of printing presses, and the control of the ink-water balance is difficult to grasp. Therefore, the operator's technical level, basic knowledge and skills are all higher requirements. According to reports, in the offset printing industry, less than one-third of the basic requirements of the lead printer can be seen, it is obvious that it is difficult to cultivate a relatively good offset printing machine.
In summary, in the past 10 years, China's newspaper printing has achieved offset printing, and offset printing has played a significant role in the development and progress of China’s newspaper industry. However, with the rapid development of printing technology, the use of offset printing in newspaper printing is not the best choice. This trend has been proved by the development trend of European and American newspaper printing. In the future, China's newspaper printing should adopt flexographic printing technology on the basis of continuing to improve printing quality and reduce costs.
Application of Flexo Printing in Newspaper Printing
After many years of development, flexo printing technology has made remarkable progress. Especially in recent years, the key technology of flexo printing has made major breakthroughs, thus creating extremely favorable conditions for the application of flexo printing in the newspaper printing industry. It can be considered that the flexo printing technology has been increasingly perfected and has entered the stage of practical application in the field of newspaper printing.
1. The application of digital workflow before printing
Adopting a digital workflow is an important part of improving timeliness, reducing costs, and improving quality. Its main contents and functions include open systems, flexibility in making and editing and finally modifying files, PDF language format, electronic document exchange, trapping, and spelling. Large version and digital proofing and RIP output once. Adopting this system can not only greatly reduce the number of process steps, shorten the working hours, but also eliminate the influence of subjective factors of manual operation and ensure the quality of prepress processing. China's newspaper industry has adopted a digital process that has a good foundation. If we further improve and improve the degree of standardization and standardization, we can greatly improve the technical level of our country's newspaper prepress digital workflow.
2. Flexo CTP technology has matured
Traditional plate-making techniques use film for printing. It takes about 30 minutes to produce a color version, which is not only time-consuming, but also difficult to guarantee in terms of quality. The use of CTP technology not only greatly simplifies the platemaking process, shortens the platemaking time (the time required to produce a color plate is only 1/3 of the traditional plate-making time), but also reduces the phenomenon of dot gain, making the highlights and dark spots The loss of network points and the substantial reduction of grid connection have greatly reduced the ability of the printing plate to replicate.
At present, the world-famous prepress equipment and plate production companies have introduced practical CTP products. Representative manufacturers include Agfa, Heidelberg, Crosby Angel, DuPont, Barco, Kodak Polystar, BASF. , Hell, etc., the introduction of flexo direct plate system more newspapers to provide quality assurance with flexographic printing.
3. Flexo printing has advantages
Compared with offset printing, the use of flexo technology in newspaper printing has obvious advantages.
(1) The equipment cost is lower than the offset press. Under the same conditions of printing medium and printing capacity, the equipment cost of the flexo printing machine is about 1/3 lower than the offset printing machine.
(2) The printing speed is higher than the offset printing machine. At present, the printing speed of a flexo press can be divided into low speed (80-150 m/min), medium speed (150-300 m/min) and high speed (600-700 m/min). Since the flexo printing is light pressure printing, the sleeve printing plate can be used, the inertia unbalance force is very small, the paper is not easy to break, and has good running stability, so high-speed printing can be realized.
(3) Low weight newsprint can be used. Due to the stability of the flexo press, there is no effect of offset fountain solution on the paper properties, so flexo printing can use low weight newsprint (40-45g/m2). If thick paper is changed to thin paper, the average annual national newspaper printing paper can save about 18% (printing 54 billion yuan a year for opening calculations).
(4) The loss rate of flexo printing is low. The flexo printing machine has a shorter turnaround time, so the paper loss rate is low, about 2%, which is nearly 9 percentage points lower than that of offset printing. If we add the amount of paper saved by the use of thin newsprint, only paper will save about 27% of the paper annually. According to reports, the US "San Francisco Observer" has only used paper because of the use of flexo printing, saving $41 million annually.
4. Adoption of ink and short ink system provides guarantee for wide application of flexo
(1) Ink painting. Ink is an environmentally friendly ink that does not contain volatile organic solvents and can improve the printing environment. This is one of them. Second, the printed wastewater can be recycled after treatment, and all the waste ink can also be recycled and reused as ink. Third, the ink is a quick-drying ink, and there is almost no problem of dirtiness during printing.
(2) Short ink system. The use of a closed anilox short ink inking system can provide a stable ink for the printing plate quantitatively, and the inking performance is significantly improved. By changing the technical parameters of the anilox roller (the number of screen lines and the geometric parameters of the cells), the desired amount of ink is obtained for the printed product.
The use of a closed reverse squeegee system not only keeps the ink in a clean state during the printing process, but also maintains the ink's performance and ensures that the ink is consistent in color.
The ceramic anilox roller manufacturing technology has made a major breakthrough, can process anilox roller 1500 lines / inch or more, or 2000 lines / inch or even 2500 lines / inch high number of anilox roller. This not only greatly improves the service life of the anilox roller, but also creates conditions for high-speed, high-precision flexographic printing.
5. Good quality flexo printing
The use of flexo printing in newspaper printing has the following characteristics:
(1) Newspaper printing is mainly based on text, lines, and color blocks. Flexographic printing has the advantage of embossing, with clear graphics, neat and vivid images, and bright colors. In this regard, flexo printing is better than offset printing.
(2) It has good print reproducibility and can ensure consistent ink color.
(3) The number of screen printing screens can reach 133-150 lines/inch. With CTP technology, the resolution can reach 1270 dpi, which can meet the requirements of newspaper printing.
(4) Multi-color group printing can be easily realized, and the length of spot color printing can be utilized.
This shows that the quality of flexo printing can fully meet the requirements of newspaper printing.
In short, newspaper printing has taken a gratifying step forward from the era of offset printing and it has begun to enter a new era of flexographic printing. As a major newspaper printing country, China's newspaper printing industry should also make its due contribution.
Source: China Paper Network