Application and comparison of gravure proofer

(1) Gravure proofer proofing procedure Sequence of proofing installation 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 Proofing ink → Monochrome and multicolor proofing → Detecting 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 in 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.

The ink is transferred from the ink hole through the pores to the surface of the printing material (in some cases, the proofer also uses an electrostatically assisted ink transfer device). The drum rolls to the end of its circumference to get the largest sheet. After the rotation is completed, the large drum leaves the surface of the plate cylinder, and the plate cylinder can be cleaned and disassembled. The color proofing after the second color is repeated after the previous color is dried and the same process as described above is repeated.

Flexible packaging materials will cause the printing material to expand and contract during printing. When the printing company is making a version of the drum, there is a requirement for increments between the colored building drums, which will bring certain difficulties in proofing. Experienced operators can pass through the gaps of the outlets. Make proofs with high registration accuracy.

The Japanese machine's ink transfer is to transfer the ink to the substrate by pressing the impression roller through the gravure plate cylinder. The machine speed is generally about 30m/min, but the impression cylinder is separated from the gravure cylinder from the start to the end. The speed is not the same, because the substrate is tightly wrapped in the surface of the drum, under the inertia of the drum, resulting in faster speed, the second lap speed will be faster than the first lap.

The British machine completes the transfer of ink by pressure on the impression cylinder to drive the plate cylinder. The speed of the impression cylinder itself is kept constant. The speed of the substrate that is wrapped in the impression cylinder is the same from beginning to end. This solves the problem of the inconsistency in the rotation speed of Japanese machines.

In the proofing process, the substrate is firstly wrapped on the impression cylinder, and then the proof is printed in the printing sequence according to the characteristics of the printing and the surface printing of the platen cylinder.

The printing plate in the plate is generally transparent, and the color is first played in the proofing process, and then light colors are created on the basis of the previous color. For example, only the four-color electric image and the white plate are printed. Usually, the black version is used first. , and then hit the educational version, the magenta version, then the yellow version, and finally play the white version on the basis of these four colors. The printing sequence of the table printing plate is the opposite of the printing plate in the plate. Most of the substrates for the printing plate are opaque, and proofing is performed from the light-colored version to the dark-colored version. When proofing, you must also pay attention to the important factor of proofing ink.

The gravure proofer does not have an ink tank. When the impression roller is in close contact with the gravure plate roller, the ink to be dispensed is manually poured onto the gravure plate cylinder. Because the speed of the proofer is not high, it is determined that the viscosity of the ink used for proofing should not be too low, otherwise it will cause a paste plate.

High-speed gravure printing machine can be opened to 160m/min under normal circumstances, the ink viscosity is about 16s, but the ink viscosity used in gravure printing should be adjusted to about 20s. The slow speed of proofing, the large viscosity of the ink and the low hardness of the rubber on the impression cylinder are all conducive to the full transfer of the ink to the substrate, and the color of the proof is relatively bright.

If the proofing does not add ink to dilute the ink, it will make the printing company suffer too much, because the printing company is difficult to print a very bright and bright color effect. It is necessary for the platemaking company to dilute the ink when proofing, so that the printing company will be much easier to do color proofing according to the gravure proofs. In the entire gravure platemaking process in which electric sculpture has achieved no film engraving, the department with the most human influence factors is the gravure proofing workshop.

The dilute of the proofing ink, the difference in dilution, the different pressure between the gravure plate cylinder and the impression cylinder, the angle of the blade, the installation method and the different pressure, the distance between the blade and the embossing point will be different. This kind of effect has an effect. In the proofing process, the relevant parameters should be adjusted according to the different substrates, surface printing and in-print characteristics, so that the perfect gravure proofs can be produced and the professional production level of the plate-making company can be played.