During the proofing process of the gravure proofing machine, the impression cylinder presses the substrate on the surface of the plate by pressure. When separated, the substrate absorbs the ink in the gravure mesh to form an image.
The quality of the image transfer depends largely on the outermost rubber of the impression cylinder. The outer rubber hardness of the rubber cylinder of the gravure proofer is generally 65 Shore hardness, which is slightly lower than the hardness of the impression cylinder used by printing companies.
The pressure distribution produced by the impression cylinders of different hardness is different. The deformation of the cylinder with low hardness under the same pressure is greater than that of the cylinder with higher hardness. The elasticity of the rubber deformation can cause the substrate to elastically deform. This results in a larger area of ​​contact between the substrate and the gravure cylinder, attracting more ink to the surface of the substrate. The rigidity of the impression cylinder produces less deformation, and the contact area with the intaglio printing plate cylinder is smaller, so the ink absorbed by the printing material is less. The hardness of the rubber is not the same, and the difference in the performance of the printed products in the highlight part is also obvious, especially when the paper is proofed, blank spots will be generated in the highlight part. This phenomenon has a lot to do with the V-shaped structure of the electric engraving network.
The British machine added an auxiliary electrostatic ink absorption device during proofing, which can solve the problem of high light white point well. The registration device occupies a very important position on the concave prototype, first of all, it is required to have a good registration accuracy. Once the registration error is greater than 0. 2mm, the effect of the electric subdivision on the concave sample will be greatly affected. It is generally required that the first loop of the concave prototype does not have registration errors.
After each color is printed, a positioning stop under the impression cylinder will stop the impression cylinder at the position where it was last stopped. When the impression cylinder and the gravure cylinder are close again, their squeeze points are the same as the last time. The positions of the squeeze points are consistent, ensuring the registration accuracy of the proofing.
A big flaw of the domestic imitation machine is that it does not pass the registration accuracy. Secondly, the registration device is required to have great flexibility. The length of the gravure plate cylinder varies greatly, the short one is only 400mm, and the long one may reach 1600mm, and the registration line on the plate cylinder does not have a fixed position, some is on the pattern, and some simply does not have a registration line . As long as these plate cylinders can be installed on the proofing machine, accurate registration proofs are required. Therefore, the flexibility requirement of the proofing machine registration device is relatively high.
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