Preparation before installing the printing plate

2022-09-19
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Preparation before installing the printing plate (plate)

before installing the printing plate, you should have prepared cushion materials with appropriate shape and size on hand. The lining material should be stone or polyester material rather than paper products, because paper is easy to absorb moisture and shrink. The width of the backing material should be the same as that of the printing plate or slightly narrow (such as 1//8 inch or 2/3 mm). If it is too wide, it is easy to absorb the liquid on the fountain roller. The backing material can be cut according to the size of the old printing plate

inspection and handling of printing plate

when handling the printing plate, hold the paper teeth and the edge of the tail of the printing plate to prevent damage to the protective layer of the blank part of the printing plate. Put it on a clean, dry, flat surface that is directly cooled by cold water, and check it against the standard version. The inspection contents include whether there are scratches or other undesirable defects

according to the manufacturer's instruction manual, you can make some small corrections to the printing plate by etching and gluing, or you can use a knife to scrape it and then apply ink or plate making ink to make small changes to the graphic and text parts. However, when making major changes, you should remake the plate. Determination of the backing material to determine the thickness of the backing material, we must first measure the thickness of the printing plate. A bench micrometer installed on the workbench is more suitable in the printing workshop, because it can measure both elastic and rigid objects. If there is no such micrometer in the printing workshop, it is better to use a paper micrometer, which is better than a mechanical micrometer. Because the surface of the former is larger, if the elastic object is measured, the value is more accurate

place the printing plate flat on a flat table, measure the thickness of at least three places and calculate the average value. If a paper micrometer or a mechanical micrometer is used, the printing plate should be flattened and pressed as much as possible to ensure the measurement effect. The thickness of the liner can be calculated according to the following method: the separation rate of the collet of the universal testing machine of the printing plate should be kept as constant as possible and the thickness should be within the range of the specified stress rate: the size of the roller anti rolling pillow (that is, the difference between the radius of the roller and its pillow, also known as the depth of the sink) and the height difference (the height difference between the highest point of the printing plate and the roller pillow on the printing plate cylinder after the printing plate liner). Some machine manufacturers believe that the printing plate should be flush with the roller pillow, but the usual practice is that the printing plate is slightly higher than the roller pillow. The sum of sink depth and roller pillow height difference is equal to the sum of plate thickness and pad thickness. The result of the depth of the sink plus the height difference of the roller pillow minus the thickness of the printing plate is the thickness of the backing

that is: liner thickness = sink depth + height difference - plate thickness

preparation of plate cylinder

the cylinder of most sheet fed printing machines can move circumferentially and laterally, and its plate fixture can also be adjusted in one or more directions. Therefore, before installing the printing plate, the drum and fixture should return to the "zero" position, and the drum must be kept clean

according to the instructions, position the printing plate circumferentially when necessary. First loosen the circumferential positioning fastening screw of the plate cylinder and return it to the zero position. (pay attention to tighten all screws after adjustment)

return the plate tail clamp to the zero position, that is, adjust the clamp to the lowest point (towards the barrel); Then move it to the center of the two roll pillows and tighten the fastening screws by hand. If the fixture of the printing machine is a decentralized device, that is, it is composed of several groups of sub fixtures, each sub fixture should return to zero according to the instructions. Return the main fixture to zero according to the instructions to determine the starting point of setting. Then position it in the middle of the printing cylinder, and then tighten the screws

use a suitable solvent to clean the ink, gum grease and lining material particles on the surface of the drum, and remove all rust. Apply a little more engine oil to prevent rust and facilitate the installation of gasket

plate installation

each printer manual has a detailed introduction to plate installation. The typical installation steps ti0.006 are listed below:

1 Before installation, cut off the ink supply and water supply system of the ink roller and the fountain roller to prevent pollution of the printing plate. Set the printer to the "onimpression" state and screw it for two weeks to ensure normal pressure

2. Put the tail edge of the printing plate into the main fixture. If there is a locating pin, align the plate side hole with the locating pin; If not, align the center line of the printing plate with the center line of the fixture. Tighten the fastening screw in the middle

3. Insert the calculated lining material with a certain thickness into the back of the printing plate, and be careful not to bend or exceed the edge of the printing plate. By adjusting the fastening screws on the main fixture, align the scribed line on the printing plate with the marking line on the printing cylinder

4. Grasp the printing plate and lining materials by hand, and manually screw the press fixture forward bit by bit until the printing plate is inserted into the tail fixture. The pressure between the printing plate and the rubber cylinder is in the "on" state, so that the printing plate moves forward along the cylinder. Only in this way can the printing plate and the printing plate cylinder reach full close contact

5. When the plate is inserted into the tail clamp, clamp the clamp. However, before fastening the fixture, slowly and manually adjust the printer to rotate forward until the tail of the printing plate just reaches the contact line between the printing plate cylinder and the rubber cylinder. The purpose of this is to put the printing plate into the fixture and minimize the lateral displacement of the fixture at the end of the printing plate. Tighten the fastening screws from the middle to both sides. If the printing machine is equipped with quick clamps with eccentric devices, they can be clamped directly to the printing plate. Refer to the operating instructions of the printing machine for the correct adjustment method

6. Fix the printing plate at right angles as far as possible through the middle fastening screws. Tighten the fixing screw, not the tightest, but also make it degree when pulling the edge of the drum groove

7. Tap the side of the drum body with your finger joint. If the printing plate is not closely combined with the cylinder, it will sound empty. If it does sound empty, it is necessary to tighten the screws of the tail clamp while tapping until the printing plate, liner and drum are closely combined. Then set the printer to "offimpression" state, and then manually turn it forward for two weeks

if any surface of the printing plate bulges, the installation is not straight enough. In this case, try to loosen the fastening screws of the tail clamp, push the tail of the printing plate towards the middle of the printer, and then tighten the fastening screws of the tail clamp. If this is not enough, you need to disassemble and reassemble

for whatever reason, when it is necessary to remove the printing plate, loosen the fastening screw of the tail clamp or the quick eccentric clamp, and then take the printing plate out of the clamp. Hold the printing plate and lining materials by hand to prevent scratches, and manually reverse the printing machine. Remove the clamp screw or quick eccentric clamp to take out the printing plate and lining material. (end)

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