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(I) Gravure Printing Machine
Proofing operation sequence Install proofing material 10 Adjust the pressure of the proofing material → Insert the positioning pin → Adjust the ink → Check the ink viscosity → Install the plate cylinder → Set the squeegee pressure → Plate cylinder positioning → Apply the proofing ink → Monochrome and more Color proofing → testing proofing proofs
(2) When the gravure proofer proofing process is used for proofing, the impression cylinder presses the substrate on the surface of the printing plate by pressure, and the substrate absorbs the ink in the intaglio network cavity to form an image when the substrate is separated. The quality of image transfer depends to a large extent on the rubber on the outermost layer of the impression cylinder. The hardness of the outer rubber on the gravure roller of the gravure proofer is generally 65 Shore, which is slightly lower than the hardness of the impression cylinder used by the printing company. The pressure distribution produced by different hardness imprinting cylinders is not the same. The deformation of the cylinder with low hardness under the action of the same pressure is greater than that of the cylinder with large hardness. The elasticity produced by the deformation of the rubber can make the substrate elastically deformed. This results in a large area of ​​contact between the substrate and the gravure plate cylinder, which attracts more ink to the surface of the substrate.
The hardness of the impression roller produced by the large deformation is small, the contact area with the gravure printing plate cylinder is small, the ink absorption of the substrate is also less. The rubber hardness is not the same, and the difference in the performance of the printed product in the high light part is also obvious, especially when the paper is proofed, it will produce a blank point in the high light part.
This phenomenon has a lot to do with the V-shaped structure of the electronic engraving version. The British machine added an auxiliary electrostatic ink-absorbing device during the proofing, which can solve the high-light white point problem. The register device occupies a very important position on the concave prototype, first of all it requires a very good registration accuracy. Once the registration error is greater than 0.2mm, the effect of the concave pattern on the power map will be greatly affected. In general, the first circle of the concave machine must not have registration errors.
After each finish, a positioning stop below the impression cylinder will stop the impression cylinder at its last stopped position. When the impression cylinder is again close to the gravure cylinder, their squeezing points are the same as the last time. The position of the pinch points is the same, which ensures the accuracy of proofing. One of the major drawbacks of domestic imitation machines is that they are not accurate in terms of register accuracy. Second, the registration device is required to have great flexibility. The length of the gravure plate cylinder varies greatly, the short is only 400mm, the long one may reach 1600mm, and the platen lines on the plate cylinder do not have a fixed position, and some are on the pattern, and some simply have no platen line . As long as these plate cylinders can be mounted on the proofing machine, accurate proofs are required to be printed. Therefore, the flexibility of the proofer registering device is relatively high.
In order to perform multi-color registration and obtain color proofing effects, the following operations must be coordinated:
1, printing materials must be wrapped under a certain tension to the drum;
2. The first color plate cylinder is installed between the top of the two chucks or the swing arm bearing;
3, move the drum, close to the surface of the plate cylinder, turn to its locked position, using a pin to secure it in a safe state;
4. Rotate the plate cylinder and align the transverse gauge line of the Huai Town with the horizontal line of the surface of the roller;
5. The large drum relies on the printing plate roller and reaches a certain pressure;
6. Check the registration status and repeat until the gauge is fully aligned.
7. Adjust the squeegee to form an appropriate degree of parallelism with the roller surface, and then adjust the vertical direction so that the squeegee is good;
8. The ink is applied to the squeegee along the surface of the roller, and then the locking pin is set aside;
9, drive the drum, drive the driven plate cylinder rotation, through the squeegee, the formation of "imprint" in the contact between the drum and the plate cylinder.
Gravure proofer proofing process features
Gravure proofer proofing process features