In the offset printing process, often encounter the phenomenon of false color printing, printing on the printing part of the field is mainly spotted or made false or incomplete text lines, image halftoning reproducibility or dot loss. There are many reasons for the ink printing process is not true, the factors involved there are many, including the performance of the paper, the performance of the ink, printing quality, printing blanket quality, printing pressure, printing machine performance and printing technology.
If in the printing process, stable performance of paper and ink, printing plate making quality to meet the requirements of printing, printing machine work performance is relatively stable, there is a color printing false phenomenon, the main reason is the printing pressure problem. In offset, the printing pressure depends on the size of ink transfer in the printing process, if the printing process of local uneven pressure, will lead directly to the printing ink is not real.
In the offset blanket, the compression deformation is the fundamental guarantee of the printing pressure, deformation of the printing ink transfer blanket is compressed. Therefore, the printing pressure size and uniformity and used in offset printing blanket has a direct relationship.
Coated in the roller blanket, also influenced by tension and printing pressure, with the increase of rolling times, blanket compression deformation stress accumulation, the blanket will become stiff, loss of flexibility and high elasticity of the original, even in the blanket surface will appear bright or crack traces, which leads to the printing process local printing pressure is not uniform.
另一个方面,由于橡皮滚筒安装在印版滚筒和压印滚筒之间,橡皮布上的每个微小单元每旋转一周,都要分别和两个滚筒各接触一次.因此,其受力是周期性变化的, 正是由于橡皮布受力的周期性变化,会导致橡皮布产生内耗,导致橡皮布的老化,影响印刷压力的均匀性,可能导致橡皮布的报废.特别在现代高速胶印机上, 橡皮布受力周期的频率较高,橡皮布产生的内耗更大,橡皮布的寿命会更短,对印刷压力的影响也会越大.
On the other hand, because the rubber roller is installed between the plate cylinder and impression cylinder, each small unit on the rubber blanket per rotation, are respectively and two cylinders each contact at a time. Therefore, the force is periodic, it is because of the periodic change of blanket stress, causes the blanket of internal friction of rubber blanket, lead to aging, affect the uniformity of the printing pressure, may cause the blanket scrap. Especially in the modern high-speed printing machine, rubber blanket by high frequency cycle internal friction force, produce bigger blanket, the blanket of life will be shorter, the effect of printing pressure will be greater.
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