Lithography of printed matter 2

In order to promptly discover the quality of the printed matter, every 200-300 pages in the printing process should be sampled once and the sample taken should be routinely inspected. After the printing of each sheet of the vehicle is completed, the personnel concerned must press the standard printing sample to recheck the inspection to ensure that the printing quality and quality meet the requirements. Section III: Development of the Rotary Printing Process One Rotary Printing Development Rotation printing has developed rapidly. In response to the requirements of the times, the Rotary Printing Department was set up, and rotary printing will gradually grow.
Rotary printing, also known as rotary lithography, is the use of webs for continuous lithographic printing. Rotary printing is a kind of printing method developed in modern times. Initially, due to the undeveloped science and technology, the rotary printing press at that time was bulky, complicated in structure, inconvenient in operation, poor ink drying, difficult to control paper tension, and expensive equipment, so the market was small, but with the rapid development of science and technology , The rotary machine has greatly improved in terms of speed quality and economic efficiency, and has greatly surpassed the potential for flat sheet printing. Specifically, the history of the development of rotary printing can be divided into the following stages:
In 1865, W.Bullock pioneered a web rotary press. This can be said to be the start of rotary printing, but it must be cut before it can be printed. In 1869, the London Times technician completed the first rotary press that had been printed and then cut. This was the prototype of the current rotary press. At that time, the double-sided printing speed reached 12,000 sheets/hour. In 1930, the invention of the thermosetting ink was officially used for commercial printing. At the same time, printing in the United States began to enter the newspaper printing system, and entered the stage of rapid development.
Domestic status: Although printing has originated in China, lithographic technology has been completely introduced from foreign countries, especially the introduction of rotary lithography. This is only a matter of recent decades. In general, domestic rotation printing starts from the newspaper industry, and commercial rotary lithography has only been introduced to the country for about ten years, and our company has not introduced the rotation machine infrequently. It can be seen that there is still much potential for rotary printing in China.
Development prospects: The development of today’s era is all reflected in the common progress of the economy and culture, and the demand for it is also increasing. In the face of such a large market, rotary printing has emerged, and it has shown its rapid growth since the early 60’s. Development momentum. For example, in the United States, there were only 228 commercial rotary presses in 133 printing plants in 1961, and in January 1969 there were 729 commercial rotary presses in 286 printing plants. The turnover increased from 200 million U.S. dollars to 27 trillion U.S. dollars. In particular, in recent years, rotary printing has become the fastest growing printing method in Europe, the United States, and Japan. In the United States, after 1980, all lithographic printing machine manufacturers mainly produced rotary lithographic printing machines. It can be seen that rotary printing has an important position in the printing industry with its obvious advantages of high efficiency, high quality, and low cost. We have every reason to believe that in the upcoming new century, there will be even more splendor in rotary printing. Prospects.
The structure of the second turn machine:
1. Paper supply unit Since the web press prints on a web, the paper supply system is mainly responsible for supplying paper, controlling the paper speed, tension, and edge position so that it can stably supply the paper to the printing unit. The paper supply system can be divided into two parts, one is the paper feed frame, and we can see in the figure that it is mainly used for the support and stability of the paper roll. The other part is the paper guide roller system, which is mainly used to provide the required tension of the roll paper and the left and right paper gauge positions.
2. Drying Units In commercial rotary printing, thermosetting inks are generally used. Thermosetting inks generally have high gloss and low viscosity properties. They need to be heated to a certain temperature to be dry, that is, most of the solvents in the ink evaporate when they pass through the drying oven. This allows the ink and the pigment in the ink to evaporate. Through the cooling roller fixed on the paper surface. Most of the current use of hot air drying, fuel for liquefied petroleum gas. At present, our company is using this drying method.
3. Cooling unit paper through the drying box, the temperature is high, the paper surface temperature up to 120-150 °C, the ink is still viscous at high temperatures, so after cooling and curing, so that the surface temperature is reduced to about 30 °C, generally The cooling roller is used to cool the circulating water, and the contact area between the roller and the paper is increased as much as possible to increase the cooling effect. In recent years, cooling cycle oil has also been used to reduce the temperature, because the specific heat of the oil is lower than that of water, and the cooling effect is small. Better. At present, our company's rotary machine uses cooling water to achieve cooling effect. 4. Folding Units The folding system used in commercial rotary printing has a large number of folding methods. Generally, it is determined according to the requirements of customers, and even some multiple folding machines operate simultaneously. According to commercial requirements, most can be more than three fold, including two fold and the third knife-fold and the third parallel fold. At present, our company mainly has 8K, 16K, 24K, 32K folding machines.
5. The printing unit The printing unit is the core of this machine. It is mainly wet, ink, printing plate, rubber four parts. Printing is accompanied by rotation. First, water is supplied and then ink is supplied. After the ink on the plate is inked, it is transferred to the blanket first, instead of being directly transferred to the paper. The rotation between the blanket cylinder and the plate cylinder is During the process, the blanket cylinder is also in contact with the roll, which transfers the text to the paper. In the printing process, the rotation of the machine is carried out at the same time, that is, some of the printing plates accept moisture, and some receive ink. At the same time, some transfer the ink on the blanket to the paper and repeat printing. We know that the transfer of ink can not be separated from the pressure, in the rotary printing, both sides of the rubber roller under pressure at the same time for ink transfer. In the actual operation, the above process is performed on all the rollers at the same time. Therefore, as shown in the figure, the paper passes through the middle and can be printed on both sides at one time, and the graphic and text can be transferred to the paper accurately and quickly.
Third, the characteristics of rotary printing:
1. Advantages (a) Printing speed, high productivity, and printing on both sides. The speed of rotary printing presses can reach 100,000 sheets/hour in newspapers and 80,000 sheets/hour in commerce. Although most of them are currently 3 to 50,000 sheets/hour, their speed is higher than that of Zhang Pingji (mostly Faster than 15,000 sheets/hour), it can also be double-sided printed and folded. (to be continued)