Offset technology: teach you how to avoid offset defects

According to statistics, the most common printing defects in the offset printing process are not paper inks and other materials, nor the operation method, but the printing machinery failure. Even if a new offset press is produced, it will malfunction during work due to some defects in design assembly and installation and commissioning.

Domestic offset printing machine parts are not up to standard

An offset press consists of tens of thousands of parts, and the manufacturing precision of each part is extremely important. Due to the limitations of the working machine and operating technology of the machined parts, some parts do not reach the advanced level, which also causes mechanical failure. A factor.

Processing quality of the main parts of the offset press

Some offset printing machines, such as the gears and rollers in the main machine, have good processing quality, but the technical performance of the matching parts is poor, which will also bring trouble to normal printing. For example, some vacuum water tanks equipped with water dispensers and water can not meet the vacuum requirements. Automatic watering often fails, resulting in water bucket and plate surface water shortage. The operator does not pay attention, and the dirty paste on the printed product will be faulty.

It is also important to install and commission the offset press.

Many plants ignore ground strength and hardness issues when they are working on a foundation before installing a machine. Now the medium and high speed offset presses have extremely high requirements on the level of the machine base: the horizontal allowable horizontal error cannot exceed 0.08/1000, the horizontal horizontal error cannot exceed 0.04/1000, and the horizontal level of the machine base is used to adjust the foot screw. For example, there are 8 correction screws under the base of J2108, and the contact point of the screw is 200px square iron. After correcting the level, use the nut to fasten the base to prevent the foot screw from moving. The problem is: the base of the machine is not on the ground. Supported by 8 foot screws, because the oil pan is to be placed below, it is impossible to seal with cement. Therefore, the surface strength of the foundation is required to be high, and the specification uses 200 cement, and the actual use of 400 cement is better. And the steel bar is rolled on the upper layer of the foundation, otherwise the cement is easily damaged or cracked after the ground screw is touched, and the machine loses its level. In particular, the roller journal and the bushing wear quickly, which may cause printing failures such as ghosts and bars.

Machine aging wear

After the machine has been used for a certain period of time, various faults will occur due to the wear and tear of the parts and the decrease in accuracy. The wear and tear of the parts is slow and slow. In addition to the factors of poor maintenance, it is also related to the materials used in the machine parts and the manufacturing process. For example, the paper feed ball made of glue wood is easy to wear into an oval shape, causing the paper to be skewed. Another example is that the universal joint shaft and the fork joint with uneven force will cause paper feed failure after wear. Embossing the shaft swinging rod and the ball, due to the large uneven force, the push pin is loose, broken, and the ball bearing is broken, resulting in inaccurate overprint or equipment accident.

The surface of the drum is also worn. For example, the impression cylinder of the imported Roland four-color machine is made of ductile iron with good wear resistance. However, after printing the same specification, the surface of the impression cylinder will occur at the edge of the paper. The linear wear and depression, so that when the product of larger size is reprinted, a white bar appears on the mark, which affects the quality of the product.

Offset printing machine maintenance is critical

The offset press should be cleaned, maintained and refueled frequently to work properly. If the maintenance is not good, the fuel is not working, and more faults occur. If the roller of the offset printing machine of a factory is full of ink and glue to dry the dirt, it becomes a "contact roller" during the pressing process, and the roller is stretched open, causing serious wear of the roller journal and bushing. The ghosts, bars, greasy and other faults occur at the same time; some offset printers do not clean the teeth, do not refuel, the paper piles are piled up, the rust is streaked, the single bite paper rusts and bites, loses the bite force, and the printing is not printed. Quasi-, "peeling" faults are concurrent.

Mechanical wear or seizure failure caused by oil cuts is common in offset printing plants. Some factories have a refueling system, but they do not implement it. They have broken out the oil and killed the machine. Some of the offset printing machines have a pile of iron powder that is unmanned; the tubing inside the casing is broken or Equipment failure caused by insufficient oil delivery is also caused by lack of inspection. In general, equipment maintenance is not good, the system is not perfect, or the implementation is weak due to the system, which is the direct cause of many printing failures. (Editor: Zhang Wei)

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