Newspaper flexo printing application
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Flexo printing for newspaper printing began in the United States in the mid-1970s. In 1982, the United States launched a newspaper-specific flexo press. Since then, flexo printing has begun to compete with offset printing in the field of newspaper printing. The San Francisco Observatory, the San Francisco Record, and the News and Observer have all used flexo printing. And achieved good results. Today, about 30% of newspapers in the United States use flexo printing; about 14 major newspapers in Europe use flexo printing; about 25% of newspapers in Italy use flexo printing.
In recent years, flexo printing has also developed rapidly in China, but in general, China's flexographic printing technology is still in its infancy. Among the total printing volume, flexographic printing only accounts for about 1.5%, and it is mainly used for printing paper boxes and corrugated boxes. Flexo printing has not been applied in the newspaper printing industry in China.
Offset printing problem
The basic requirement of newspaper printing is that the first is time-sensitive, and the newspapers are provided to the readers at the fastest speed. The second is to meet the quality requirements, the pictures are clear, the colors are bright, and the visual effects are good. The third is economic. Under the premise of meeting the basic requirements, the cost should be minimized. The fourth should be environmentally friendly. Under the conditions of increasing environmental protection requirements of the international community, the basic conditions for printing in newspapers should be met in accordance with environmental protection requirements. Below, we will make a brief analysis of the offset printing and printing, and talk about the problem of offset printing.
1. Adjust the structure of newspaper printing
At present, in China's newspaper printing, almost offset printing dominates the world, regardless of the size and quantity of printing, all use offset printing. Europe and North America broke the single pattern of offset printing in the 1990s. We should also choose the printing method according to the specific situation. For example, the cost of offset printing for tens of thousands of newspapers will be greatly increased. At this time, different printing methods can be selected according to different requirements.
2. The paper loss rate and the high rejection rate are prominent problems in offset printing.
In offset printing, controlling ink and water balance is an important issue, and achieving ink-and-wash balance in offset printing requires a process. Under normal circumstances, it takes about 15-30 minutes of adjustment and trial printing from start-up to stable operation, which will inevitably increase the paper loss rate. In the offset printing process, there are many factors that affect the ink and water balance, and most of these factors are changed. Even under normal printing conditions, waste products may occur due to changes in certain conditions. For example, the paper loss rate of a sheet-fed four-color offset press is generally as high as 7%-15%, and the web offset printing press has a higher paper loss rate than a sheetfed offset press. Therefore, from the economic point of view, offset printing is not the most ideal.
3. Offset printing does not have much advantage in the quality of printed products.
The high quality of offset printing is based on many conditions. If the surface properties of the printing material are high, the fine printing can be printed only when printing on coated paper with higher price and better quality. Printing on newsprint is prone to the following problems: (1) the use of dampening solution in offset printing, and the newsprint is very absorbent, the whiteness of the paper will decrease after water absorption; (2) the surface of the newsprint is very rough, which will affect the clarity of the graphic. (3) In the printing process, it is easy to be affected by external factors, the printing quality is poor in stability, and it is prone to malfunctions such as uneven ink color and dim color.
4. Offset printing is at a disadvantage in environmental protection
Offset rotary printing ink is a low-viscosity solvent-based ink. The solvent content of the ink is high. Without oxidation and decalization catalyst, it is directly dried by osmotic absorption and heating. The printed product is difficult to dry fully in a few hours, not only in the printing process. A dirty malfunction occurs, and when the reader gets the newspaper, the dry ink sticks to the hand. In addition, the solvent-based ink has a strong odor and is disadvantageous to both the operator and the reader. In addition, the volatile organic solvent in the ink is polluted by the environment. Therefore, the rotary offset ink is a polluting ink, and its use should be gradually limited.
5. Offset printing has certain requirements on paper
Offset printing has a high printing speed and uses dampening solution. If the paper is too thin, it may cause a paper break. Therefore, the paper used for offset printing should not be too thin, generally should not be lower than 52g/m2, which will also increase the cost of printing.
6. Offset printing has higher requirements on the operator's technical level.
Due to the complicated structure of the offset printing machine, the adjustment position is the most in all kinds of printing machines, and the control of the ink balance is difficult to master, so the operator's technical level, basic knowledge and skills are highly demanded. According to reports, in the offset printing workers, less than one-third of the basic requirements of the leader, it is difficult to train 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, newspaper printing only uses offset printing, which is not the best choice. The development trend of European and American newspaper printing has proved this point. In the future, China's newspaper printing should use flexographic printing technology on the basis of continuing to improve printing quality and reduce costs.
Application of flexo printing in newspaper printing
After years of development, flexographic printing has made remarkable progress. Especially in recent years, the key technology of flexo printing has made a major breakthrough, which has created extremely favorable conditions for the application of flexo printing in the newspaper printing industry. It can be considered that the flexographic printing technology has been increasingly perfected and has entered the stage of practical promotion in the field of newspaper printing.
1. Pre-press digital workflow application
The use of digital workflow is an important part of improving timeliness, reducing costs and improving quality. Its main contents and functions include open system, flexibility of production editing and final modification of documents, PDF language format, electronic file exchange, trapping, spelling Large version as well as digital proofing and RIP output. The use of this system not only greatly reduces the number of processes, shortens the working hours, but also eliminates the influence of subjective factors of manual operation and ensures the quality of prepress processing. China's newspaper industry has a good foundation for adopting digital processes. If we further improve and improve its standardization and standardization, it can greatly improve the technical level of pre-press digital workflow in China's newspapers.
2. Flexo CTP technology is mature
The traditional plate-making technology uses film to print, and it takes about 30 minutes to produce a color version, which is not only time-consuming, but also difficult to guarantee in quality. The use of CTP technology not only greatly simplifies the plate making process, but also shortens the plate making time (the time required to produce a set of color plates is only 1/3 of the traditional plate making time), and reduces the dot gain phenomenon, making the highlights and dark areas The loss of the network and the reduction of the grid are greatly reduced, which improves the copying ability of the printing plate.
At present, the world-famous prepress equipment and plate production company has successively launched practical CTP products. Representative manufacturers include Agfa, Heidelberg, Creole Angel, DuPont, Barco, Kodak Polyphoto, BASF. , Hell, etc., the introduction of flexographic direct plate making system provides quality assurance for newspapers using flexographic printing.
3. Flexo printing has advantages
Compared with offset printing, the use of flexographic printing in newspaper printing has obvious advantages.
(1) Equipment costs are lower than offset presses. Under the same conditions of printing material and printing capacity, the equipment cost of the flexo printing machine is about 1/3 lower than that of the offset printing machine.
(2) The printing speed is higher than the offset printing machine. At present, the printing speed of the flexo printing machine can be divided into three speeds: low speed (80-150 m/min), medium speed (150-300 m/min) and high speed (600-700 m/min). Since flexo printing is a light pressure printing, a sleeve printing plate can be used, the inertia unbalance force is small, the paper is not easily broken, and the running stability is good, so high-speed printing can be realized.
(3) You can use low-weight newsprint. Due to the stable running stability of the flexo press and the influence of the offset fountain solution on the paper performance, the flexo printing can use low-weight newsprint paper (40-45g/m2). If the thick paper is changed to thin paper, the average annual national newspaper printing paper can save about 18% (calculated by the annual printing 54 billion pairs).
(4) Flexo printing has a low rate of damage. Flexo printing and test time are shorter, so the paper loss rate is low, about 2%, which is nearly 9 percentage points lower than offset printing. If you add the amount of paper saved by using thin newsprint, only one paper can save about 27% of paper per year. According to reports, the US "San Francisco Observatory" saved $41 million annually because of the use of flexo printing, which is only one paper.
4. The use of ink and short ink path systems guarantees the wide application of flexo printing
(1) Ink. 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 waste ink can be recycled to be reused as an ink. Third, the ink is a fast-drying ink, and there is almost no smearing problem when printing.
(2) Short ink path system. The closed anilox short ink path inking system can quantitatively provide stable ink for the printing plate, and the inking performance is significantly improved. By changing the technical parameters of the anilox roll (the number of screen lines and the geometric parameters of the cells), the prints are given the required amount of ink.
The use of the closed reverse squeegee system not only keeps the ink clean during the printing process, but also maintains stable ink performance and ensures consistent ink color.
The ceramic anilox roll manufacturing technology has made a major breakthrough in processing anilox rolls of 1500 lines/inch or more, or high-line anilox rolls of 2000 lines/inch or even 2500 lines/inch. This not only greatly increases the service life of the anilox roll, but also creates conditions for high-speed, high-precision flexographic printing.
5. The quality of flexo printing is good.
The use of flexo printing in newspaper printing has the following characteristics:
(1) Newspaper printing mainly focuses on characters, lines and color blocks. Flexo printing has the advantages of embossing, clear graphics, clean and vivid picture, and bright colors. In this respect, flexo printing is superior to offset printing.
(2) It has good printing repeatability and can ensure the ink color of the printed products is consistent.
(3) The number of screen-added screens can reach 133-150 lines/inch. With CTP technology, the resolution can reach 1270dpi, which can meet the requirements of newspaper printing.
(4) It is convenient to realize multi-color group printing and play the long-term printing of spot colors.
It can be seen 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 has begun to enter a new era of flexographic newspapers. As a newspaper printing country, China's newspaper printing industry should also make due contributions to this.