Analysis of offset printing unit

Printing unit

The printing unit is the core of the printing press. It directly determines the quality of the printed product. The paper feeding and receiving sections serve the printing unit. The printing unit is a critical part from the point of view of design, processing, and installation and commissioning. Therefore, it is important to improve the quality of printing products by comprehensively mastering the debugging principles of printing units.

1. The composition of the printing unit

The role of the printing unit is to complete the transfer process of the ink to the printed sheet. More simply, this completes the printing process. In order to achieve this process, what kind of structure should be used? In the following, the composition of the printing unit will be analyzed with the stamp as an example.

To stamp on a piece of paper, first the stamp should have certain content, such as the name of the person and the name of the institution, etc. The paper should then be placed on the surface of a table or other object, and the stamp with the dye attached should be Press hard on the paper, the result is to transfer the contents of the stamp to the paper. When the strength does not change, the clarity of the stamp is not the same; after several chapters are covered, the content of the chapter becomes less and less clear. If you want to continue to cover, you must use the stamp to re-stick the dye. When the stamp is completed, the stamp is sealed up. Each time the seal is stamped, the contents of the stamp remain unchanged. The stamp is called a printing plate. Paper must be placed on the surface of a table or other object, otherwise it will not be pressure. The table supporting the paper is called an imprinting platform. Putting the stamp on the paper may cause the dye to transfer to the paper. This is actually a pressure-compression process. This mechanism is called a pressurizing mechanism. When there are many stamps, it is necessary to continuously add dyes, so it must be equipped with a mechanism for conveying dyes, that is, an ink transfer mechanism. After stamping, seals should be sealed. This is actually a pressure-relieving process. This mechanism is called a pressure-relief mechanism. Sometimes the strength of the stamp is not the same, but always hope that the pressure can be kept constant. The mechanism that makes the pressure constant while changing the pressure according to the specific situation is called a pressure regulating mechanism.

From the above analysis, it can be seen that the process of stamping is actually the simplest printing process. It includes: "ink transfer mechanism", "printing plate", "imprinting platform", "disengagement pressure mechanism" and " Pressure Regulating Mechanism" This is the structure of the original letterpress printing press. However, people find that when the seal is stamped with hard stamps, although the contents of the stamp are clear, discontinuous phenomena sometimes appear, and people later use rubber stamps. Because the rubber stamp is relatively soft, it can be in close contact with the surface of the paper when force is applied, so no disconnection occurs. This led to the invention of the offset press.

Offset printing presses are relatively complex in structure than letterpress printing presses. First, it adopts a discontinuous printing method that uses a blanket as an intermediate medium to transfer ink, thus increasing the installation of rubber. Second: Since it adopts the principle of ink repellency to transfer ink, an additional water delivery mechanism must be added. The speed of stamping is far from satisfying people's needs, so the printing press was changed from the original manual mechanical platform type, and now it is changed to mechanical rotation type. In summary, the printing unit of a modern offset press is generally composed of an ink transfer mechanism, a water delivery mechanism, a plate cylinder, a blanket cylinder, an impression cylinder, a clutch pressure mechanism, and a pressure adjustment mechanism. Although there are many types of printing presses today, they will never change, and as long as they are analyzed in detail, they can find most of them. Having mastered the working principle of each part and the mutual cooperation between each part, debugging the printing unit will be handy.

2. Roller section

The roller section is one of the most basic components of a printing press. The most basic structure of an offset printing press is three rollers, namely a plate cylinder, a blanket cylinder, and an impression cylinder. The ink is transferred from the printing plate to the blanket cylinder and then transferred by the blanket cylinder to the impression cylinder to complete the printing. The rubber roller used in the middle actually only plays a role in transferring ink, so this printing is often called indirect printing. This is the most obvious feature of the difference between offset printing and other printing methods. Although the basic composition of the three rollers has not changed, it has evolved and produced a variety of printing presses.