Printing unit
The printing unit is the core of the printing machine. It directly determines the quality of the printed products. The paper feeding and receiving parts serve the printing unit. No matter from the perspective of design, processing, installation and debugging, the printing unit is a very critical part. Therefore, it is of great significance to comprehensively master the debugging principle of the printing unit to improve the printing quality.
1. Composition of printing unit
The role of the printing unit is to complete the transfer process of ink to the printed sheet, more simply, this completes the printing process. What kind of structure should we have to realize this process? The following takes the stamp as an example to analyze the composition of the printing unit.
To stamp on a piece of paper, first of all, there should be certain content on the stamp, such as the name of the person and the name of the institution, etc. Second, the paper should be placed on the surface of the table or other objects, and finally the stamp with the dye stuck on it Press hard on the paper, and the result is that the stamp content is transferred to the paper. When the strength does not change, the clarity of the stamp is also different; after a few chapters are covered, the content of the chapter becomes more and more unclear. If you want to continue to cover, you need to use the stamp to re-stick the dye. When the seal is finished, seal the seal. Each time the stamp is stamped, the content of the stamp remains unchanged, and the stamp is called a printing plate. The paper must be placed on the table or the surface of other objects, otherwise it will not form pressure, and the table supporting the paper is called the imprinting platform. It is possible to transfer the dye to the paper only when the stamp is placed on the paper. This is actually a compression process. This mechanism is called a compression mechanism. When there are many stamps, the dye needs to be replenished constantly, so it must be equipped with a mechanism to convey the dye, that is, an ink infusion mechanism. After the stamping is completed, the seal should be sealed up. This is actually a decompression process, and this mechanism is called the decompression mechanism. Sometimes the strength of the stamp is different, but I always hope that the pressure can be kept constant. The mechanism that makes the pressure constant and at the same time can change the pressure according to the specific situation is called the pressure regulating mechanism.
It can be seen from the above analysis that a stamping process is actually the simplest printing process, which includes: "inking mechanism", "printing plate", "imprinting platform", "clutch pressing mechanism" and " Pressure regulating mechanism ", this is the structure of the original letterpress printing machine. However, people found that when stamping with hard stamps, although the contents of the stamps were very clear, sometimes discontinuous phenomena appeared, and later people began to use rubber stamps. Because the rubber stamp is relatively soft, it can be in close contact with the surface of the paper when you apply force, so there will be no disconnection. This is what led to the invention of the offset press.
Offset printing presses are relatively more complicated in structure than letterpress printing presses. First: It uses a discontinuous printing method, that is, using a blanket as an intermediate medium to transfer ink, thus increasing the mechanism for installing a rubber. Second: Because it uses the principle of ink repellence to transfer ink, a set of water delivery mechanism must be added. The speed of stamping is far from meeting people's needs, so the printing machine was changed from the original manual platform type to the mechanical rotary type. In summary, the printing unit of a modern offset press is generally composed of an ink delivery mechanism, a water delivery mechanism, a plate cylinder, a rubber cylinder, an impression cylinder, a clutch pressure mechanism, and a pressure adjustment mechanism. Although there are many types of printing presses, they are inseparable, and as long as they are analyzed in detail, these major parts can be found. Mastering the working principle of each part and the mutual cooperation between each part, debugging the printing unit will be handy.
2. Roller part
The cylinder part is one of the most basic components of the printing press. The most basic structure of the offset press is three cylinders, namely the plate cylinder, rubber cylinder and impression cylinder. The ink is transferred from the printing plate to the rubber cylinder, and then transferred from the rubber cylinder to the impression cylinder to complete the printing. The rubber cylinder used in the middle actually only plays a role of transferring ink, so this kind of printing is usually called indirect printing. This is the most obvious feature that distinguishes offset printing from other printing methods. Although the basic composition of the three cylinders has not changed, it has evolved to produce various printing machines.
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