Modern printing machines are generally composed of plate-setting, ink-coating, embossing, paper feeding and other mechanisms. When it is working, the text and images to be printed are first made into a printing plate, which is installed on a printing machine, and then the ink is applied to the place where the text and images are on the printing plate by a person or a printing machine, and then directly or indirectly transferred Printed on paper or other substrates to reproduce the same printed matter as the printing plate.
The printing presses are divided into letterpress, planographic, intaglio and stencil printing machines according to the form of the printing plate; according to the plate mounting and imprinting structure, they are divided into flat press type, round press flat type and round press round press.
The letterpress printing machine is the oldest printing machine. The graphic part of the surface of the printing plate is convex, and the blank part is concave. When the machine is working, the rubber roller coated with ink rolls over the surface of the printing plate, and the convex graphics and text are covered with a uniform layer of ink, while the concave blank part is not stained with ink. The pressure mechanism transfers the ink to the surface of the printed matter, so as to obtain a clear imprint and reproduce the required printed matter.
There are three types of letterpress printing machines: flat press, round press and round press. Flat press letterpress printing machine is also called flat press printing machine. The plate platform and the imprinting mechanism of the printing plate are flat. When working, the printing plate is in full contact with the imprinting plate. The total pressure the machine bears once is relatively large, and the relative imprinting time is relatively long. This printing machine requires that the printing plate and the imprinted flat plate are flat, and the printing format is not large; the circular flattened relief printing machine, also known as the flatbed printing machine, is equipped with a flat plate for the printing plate, and the imprinting mechanism is a circular cylinder . When the machine is working, the printing plate reciprocates, and the printing speed is limited, so the output is not high; the circular pressure relief printing machine is also called a rotary printing machine. The printing plate and the printing mechanism of the printing plate are circular cylinders. When the machine is working, the impression cylinder moves with the printed matter and contacts with the plate cylinder. The impression cylinder and the plate cylinder continuously and rapidly rotate, so the productivity is high.
The graphic part of the printing plate surface of the lithographic printing machine and the blank part are almost on the same plane. It makes use of the principle of water and oil repellent to make the graphic part resistant to water and oil, and the blank part to resist oil and hydrophilic without sticking to the ink. Under pressure, the ink in the ink part is transferred to the surface of the printed matter to complete the printing process.
After adopting the indirect printing method, lithographic printing machines have developed rapidly, and there are many varieties, such as office micro-offsets, large-scale, multi-color, high-speed book and magazine offset printing presses, used for flat sheets or webs, Single-sided or double-sided lithographic printing machine. Among them, monochrome offset presses and web offset presses are representative. Lithographic printing machines have widely adopted electronic computer control devices, which are becoming more and more advanced in technology. Plate-making equipment has also been developed to use electronic color separation machines, and pre-coated photosensitive plates are widely used.
The main feature of the gravure printing machine is that the graphics and text on the printing plate are concave, and the blank part is convex, which is exactly the opposite of the layout structure of the relief printing machine. When the machine is printing monochrome, the printing plate is first immersed in the ink tank and rolled, and the entire printing plate surface is coated with ink layer. Then, the ink layer belonging to the blank part on the surface of the printing plate is scraped off, the convex part forms a blank, and the concave part is filled with ink. The deeper the concave part, the thicker the ink layer. The machine transfers the ink in the recessed part to the printed matter by the action of pressure to obtain the printed matter.
When printing multi-color, the overprint method or indirect partial ink coating method is used to make inks of various colors be distributed on the relevant parts of the printing plate surface as needed. The basic printing principle of multi-color printing is the same as that of monochromatic printing. There are two main types of printing plates used in gravure printing machines, one is photogravure, that is, photocopying plate; the other is engraving plate. The engraving of the engraved version includes manual engraving, mechanical engraving and electronic engraving.
The screen printing machine belongs to the more representative printing equipment in the stencil printing machine, and its printing plate is a silk screen which is woven by materials such as silk and has a crisscross pattern with distinct warp and latitude. We have produced a variety of screen printing machines such as plane, curved surface, forming, printing and dyeing, printed circuit and new type rotary. Among them, the speed and productivity of the new rotary screen printing machine is relatively high. Its characteristic is that the screen is installed on the cylinder, and the ink is poured into the cylinder. When the machine is working, the cylinder rotates, and the rubber squeegee quickly prints the pattern onto the printed matter.
Besides silk, nylon wire, copper wire, steel wire or stainless steel wire can also be used to make wire mesh. The principle of stencil printing applied to screen printing machines originated from ancient stencil printing. There are many forms of stencil printing, such as transcript printing, hollow printing and silk screen printing.
Screen printing was initially performed manually, at the time there was only one plate holder, one screen plate and one template. It was not until the 1950s that screen printing was mechanized and automated. The cylinder screen printing machine has a large amount of ink during printing. It is suitable for printing thick printed materials. It can be printed on a variety of paper, glass, wood, metal, ceramic, plastic or cloth. A variety of inks can be used, including conductive Metallic ink.
Modern printing machinery is further developing towards high speed, high efficiency and high quality. Large-scale, multi-color, multi-function, as well as automated, linked, serialized models and models are also increasing day by day.
For example: on the basis of the original main type, combining the same type of unit can make single-sided and monochrome printing into single-sided and multi-color printing, and can also change double-sided and monochrome printing into single-sided and double-color Printing; combining different types of units, it can be recombined into various combined printing machines such as offset printing, gravure printing and embossing printing according to needs.
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