The five basic requirements of the printing plate cylinder, must do!


Published on:

2017-04-21

As the saying goes, the print "three points in the printing, seven points by the plate". What to pay attention to during the printing plate making process, how to choose and test the plate cylinder, is the premise of the quality assurance of printed products. This article will introduce the basic requirements for gravure printing cylinder selection and processing, plate plating and cylinder grinding, for reference.

The five basic requirements of the printing plate cylinder, must do!

As the saying goes, the print "three points in the printing, seven points by the plate". What to pay attention to during the printing plate making process, how to choose and test the plate cylinder, is the premise of the quality assurance of printed products. This article will introduce the basic requirements for gravure printing cylinder selection and processing, plate plating and cylinder grinding, for reference.

1, gravure cylinder selection and processing

Gravure cylinders should be well selected and processed. Gravure cylinders have open hollow cylinder and closed solid cylinder, and the length and perimeter of the cylinder are determined according to the size of the gravure printing machine and the printed material. The best way to make the cylinder is to process it directly with seamless steel tubes, which can be seen from the inside of the finished product, which is smooth and free of interfaces.

The processing of the printing plate cylinder is divided into roughing, semi-finishing and finishing. Rough processing of the plate cylinder wall thickness to meet the provisions to ensure that the weight of each part is consistent. The centrifugal force generated during engraving and printing rotation is also the same. Semi-finishing is to keep the shaft concentric with the plate cylinder, some do not need to process the shaft parts, but the flange processing on both sides should be the same.

Finishing is to fine turn the outer circle of the plate cylinder to make it reach the design specified size. The processing accuracy of the plate cylinder is directly related to the service life of the plate cylinder and the plating and electro-engraving effect of the plate cylinder, up to the final product printing quality. After processing the plate cylinder, the wall thickness should be uniform and the indicators should meet the quality standards.

2, plate plating

Plate cylinder plating should be fine, copper layer to meet the standard, copper plating before the plating to carry out pre-treatment. First of all, the oil on the surface of the plate cylinder is removed by hand or electrolysis. Then the plate cylinder is pickled and the rust and corrosion oxide film on the surface of the plate cylinder is corroded with chemicals, and finally a layer of base nickel is plated on the surface of the plate cylinder. Then copper plating, copper plating is very important, copper layer is the engraving layer of the gravure plate cylinder, the printed part of the graphics on this layer completely by the electronic engraving machine engraving. Copper plating is directly related to the quality of engraving graphics.

3, cylinder grinding

The plate cylinder grinding process should be good. Copper-plated plate cylinder, the need for copper layer surface grinding, so that the surface finish of the printing plate cylinder to △ 8 ~ △ 10, only good grinding, the later plate cylinder finish can be guaranteed, especially when it comes to a large area of flat or excessive network, if the copper layer surface finish does not meet the requirements, it will show the printed products have spots, water lines, grinding channels, flush stubble and other problems.

4, electric engraving quality

The quality of the electrical engraving of the printing plate should be up to standard. In order to ensure the quality of electronic engraving gravure, the industry standard specifies the size and depth of the engraving cavity. However, the size and depth of the cavity is affected by the model (different companies' products carve out different cavity shapes), the number of wires, the newness of the engraving needle, the angle of the engraving head, the thickness of the copper layer and product quality requirements, there are more variable factors, with 70 lines / cm, the angle of the wire is 30 degrees, using a new 120 degrees engraving needle as an example, the test engraving cavity width: 34~36um for high light and 175~178um for dark tone. 175~178um.

This value is slightly smaller for the black version if fine text and clues are encountered. General conditions under the magnifying glass, absolutely no net wall missing or net cavity incomplete phenomenon, if any, the lines are not real, there are false edges, flat net field blistering, etc.

5, chrome layer quality

The hardness of copper is generally in HV90 ~ 180, printing ink scraper is easy to scratch the printing plate. Due to the high hardness of metal chromium, in HV800 ~ 1000, wear resistance and good, so when the printing plate cylinder graphics production is complete, but also in the copper layer surface chromium plating to improve the printing resistance. Printing occurs in the chrome will not only damage the printing plate, but also bring a lot of scrap to the printer, resulting in losses. Therefore, in the inspection of the printing plate cylinder to pay special attention to the plate whether there is the phenomenon of chromium off the skin, once found immediately returned to repair, do not use.