Lithography of printed matter 1

Section I: Lithographic Offset Presses Lithographic presses now use an indirect structure that is printed on an intermediate-rubber roller for printing. Therefore, lithographic printing presses are often referred to as offset printing presses.
Lithographic offset presses, except for round press proofers, are all circular presses, but there are many types. There are manual feeds and automatic feeds; there are single-sided presses and double-sided presses. Printed; Monochromatic, but also multi-color; There are sheets of paper printed, but also a web printing; There are full-open, open, and four open; In addition, some lithographic offset The machine is also equipped with a drying device and a folding device.
No matter what kind of lithographic offset printing press, as shown in Figure 9-4, it consists of five parts: feed mechanism, ink supply mechanism, wetting mechanism, and delivery mechanism.
(1) Paper feeding mechanism. Consisting of paper storage and paper feeders.
(2) Printing organization. Including plate cylinder, blanket cylinder, impression cylinder. Figure 9-5 shows the configuration of each roller in a sheet-fed offset press, and Figure 9-6 shows the configuration of each roller in a web offset press.
(3) Ink supply mechanism. It consists of ink fountain, ink adjustment screw, ink output adjustment plate, ink fountain roller, ink transfer roller, ink distribution roller, ink string roller and reel roller. The arrangement is shown in Figure 9-7.
(4) Wetting mechanism. Including the bucket, the bucket roller, the water transfer roller, the uniform roller, and the water roller, as shown in Figure 9-8.
Section II: Preprint preparation for lithographic printing. The lithography's own characteristics determine the complexity of its printing process. Therefore, it must be fully prepared before printing. Prepress preparation includes: paper cutting, school edition, edition, water supply, ink supply, and paper. The first is the preparation of paper. Due to the need of printing size, the printed paper must be cut as required.
In order to reduce errors that may occur after the printing plate is on the machine, the printing plate must be rechecked before printing. The contents mainly include: the blue color, the specification, the printing stone, and the printing color.
After the proof plate, it can be fixed on the plate cylinder. In order to ensure the quality of the printed matter, it is necessary to grasp the tightness of the upper version when it is operated on the upper version. Too loose will result in inaccurate overprinting, and too tight will cause the printing plate to burst.
In the prepress preparation process, the selected ink will be loaded into the ink fountain, and the inking device is adjusted so that the ink is uniformly transferred. In the process of applying the ink to the water, we must maintain a balance between water and ink to prevent water and ink from becoming large. Here are some highlights of prepress preparation:
1. Preparation of Printing Plates In order to reduce errors that may occur after printing plates are placed on the machine, the plates must be reviewed before printing. The contents include: printing plate thickness, printing plate type, color type, color tone, and printing plate Distance, whether or not there are bumps on the layout, and whether there is any foreign matter on the back of the plate. Special attention should be paid to the inspection of color and tone.
2. Preparation of printing ink The ink used for lithographic printing must have the characteristics of easy printing, that is, it can be smoothly drawn from each ink fountain and passed through the ink roller and printing plate to the rubber roller and printed on the surface of paper or other substrates. Offset printing is indirect printing, and has the presence of fountain solution. When the ink is transferred from the blanket cylinder to the paper surface, the amount of ink must be reduced. Therefore, the offset printing ink should have sufficient adhesion to the paper surface, acid resistance, and insolubility. Water, strong anti-emulsification, bright color, strong gloss, no discoloration after drying, no discoloration, etc. The inks used in offset printing are as follows:
A, bright offset ink has a high gloss, bright colors, clear dots, good wear resistance, is a high grade resin type offset ink. It is suitable for the printing of coated high-grade paper such as coated paper and glass powdered paper.
B. The quick-fixing offset printing ink has a good gloss and good fixing characteristics, which can reduce scratches, shorten the printing cycle, and increase the printing speed. Suitable for printing high quality paper and general paper.
C. Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset
3, fountain solution preparation In addition to special circumstances, the dampening water used in offset printing is not pure water, but contains a variety of electrolytes, surfactants and hydrophilic colloidal dilute solution. In order to distinguish it from the general water phase, we call the aqueous solution used for the wet-printing surface in the offset printing process a fountain solution, or water fountain solution. In order to make the fountain solution ratio and easy to use, the traditional method is to according to the provisions of the formula and the preparation method, a relatively high concentration of the solution is prepared, called fountain solution.
When used, dilute the original solution with a fountain solution. Dampening reduction liquids are also often used directly to erase the dirt that is present on the blank part of the printing plate, or to overcome the drawbacks of "burning paste." Due to the gradual commercialization of offset printing raw materials, there are bottles (cans) of dampening stock sold on the domestic and foreign markets. For the convenience of transportation, sales, and use, there is also the sale of each group into tablets or powders.
Many printing factories in China are still using the zinc plated-based gravure plate. The hydrophilic part of its blank part is a polar inorganic salt, a zinc phosphate layer. It is not wear resistant and has poor chemical stability. And due to a variety of physical and chemical factors, in the printing process, the graphic part may tend to expand, resulting in "burn"; and the blank part of the hydrophilic properties will be reduced, resulting in "dirty version."
In order to overcome the drawbacks of “burning” or “dirty printing”, one of the main technical measures is to wet the printing plate with fountain solution during the printing process so that the hydrophilicity of the blank portion remains relatively stable.
3. Formal Printing Before the formal printing, a process of adjustment is required. The contents of the adjustment mainly include: printing color, printing specification, tangent, angle line requirements, blemishes, film outlets have been removed, printing lines register, positive and negative overprint There are also specific projects requested by the customer or the Works Branch.
Before starting the machine, you should first wipe the paper powder on the plate with water, and then use fire water to remove the ink from the plate surface stone. Then, be optimistic about the pull gauge, adjust the double-sheet system and the blowing of the paper feeder. After the official boot printing, the first printout of the qualified and printed Deejay Sheets will be submitted to the competent person for signing and approval. (to be continued)