Analysis of Gravure Printing Technology (I)

Gravure printing is one of the four major printing methods today. In contrast to letterpress printing, gravure printing has a lower graphic area on the layout than the printing plane. The depth of the surface of the printing plate is reflected in the shading of the original. If the graphic part is recessed deep and filled with a large amount of ink, the layer of ink left on the surface of the substrate after embossing is thick; the part of the picture is concave and shallow, the amount of ink contained is small, and The ink layer left on the substrate is thin. The amount of ink in the plate corresponds to the light and dark levels of the original text. During printing, the plate cylinder is first made to pass through the ink tank or the ink stick to fill the entire printing plate, and then the ink attached to the blank portion is scraped off with a squeegee to fill the ink in the hollow cavity. Under proper printing pressure, it is transferred to the substrate surface. Gravure printing has high speed (up to 300m/min), printing plate high resistance to printing force (up to 300 to 4 million printing), ink color thick, rich colors, clear and crisp, moderate contrast, vivid image, product specifications and diverse Etc. Can print on substrates such as paper, aluminum foil, plastic flexible packaging, thick paper containers, liquid paper devices, and trademarks.

With the development of science and technology, the range of gravure printing is increasing at home and abroad, and it is suitable for the printing of various materials, such as the preprinting of colored crates, and the cartons produced by gravure preprinting are of better quality than those produced by traditional methods. High strength, low cost; multi-color (up to 12 colors), high speed (300m/min or more), automation (registration automatic control and powerful control, etc.), online (continuous processing of intaglio printing and printing ) And other directions.

Gravure printing mainly includes: plate making, printing and quality control.

One, gravure plate making

At present, gravure platemaking mainly includes: direct corrosion gravure, electronic engraving gravure, laser engraving gravure, electron beam engraving gravure and so on.

The direct etching of the gravure is performed on dichromate-sensitized carbon paper. The gravure grid is first dried, and then the continuous positive adjustment image is printed. Then the image on the carbon paper is transferred to the drum and passed through. Develop, fill, and corrode to produce a printing plate. Since the direct etching of the gravure plate is mainly controlled directly by manpower, the stability of the platemaking, the uniformity of the density on the ground, the repeatability of reprinting, and the intelligibility of the characters are all poor. Generally, it is only used for ordinary plastic flexible packaging printing.
Electronic engraving gravure is the use of electronic engraving machine to directly gravure cylinder engraving. It scans the manuscript through the scanning head to obtain a density optical signal, which is photoelectrically converted into an electrical signal. After being processed by a computer, it is transmitted to the output end, drives an electronic engraving head, and carries out engraving on a copper cylinder. A gravure printing plate is made.

Laser engraving gravure is the use of laser engraving machine engraving gravure cylinder; and electron beam engraving gravure is the use of electron beam gravure engraving machine engraving gravure cylinder.

In order to ensure the quality of the electronic engraving gravure, the size and depth of the carved net holes are specified in the industry standard (see Table 1). However, the size of the cell site and the depth and random type (products of different companies), the number of network lines, the age of the cutter, the angle of the cutter, the thickness of the copper layer (hardness of the copper layer is 180 to 210) and the product quality requirements Impact, more variable factors, industry standards, only 70 lines / cm, 130 ° knife angle and the new knife as an example.

two. Gravure printing process

The gravure printing adopts the rotary printing method of the park pressure garden. Its characteristics are: the structure of the printing press is simple, the printing plate is resistant to the printing force, the printing speed is fast, the ink of the printed matter is thick, the layers are rich, and the cost is low when printing in large quantities. Gravure printing is classified in many ways and can be divided into three categories according to its purpose: book and gravure printing machines, flexible packaging gravure printing machines and hard-pack gravure printing machines. Books and gravure machines are used to print magazines, books and magazines, pictorials, etc., and are equipped with folding devices at the back; flexible packaging gravure machines are used to print packaging materials such as cellophane, plastic film, aluminum foil and paper, and can be equipped with composite, glazing, and molding. Cut the device. Plastics can be divided into two categories: sheet-fed gravure machines and web-fed gravure machines, most of which use web gravure machines. According to the printing color number classification, it can be divided into monochrome gravure printing machine and multi-color gravure printing machine. According to the arrangement of printing color group, it can be divided into a satellite gravure printing machine and a combined gravure printing machine. The satellite-type gravure printer shares several impression cylinders in several color groups. The combined gravure printing machine is horizontally arranged in each color group to form an assembly line.

Gravure printing, in accordance with the requirements of the work task list and proofs to receive ink, substrates; then install the printing cylinder; adjust the impression cylinder on the liner, so that the pressure on the various parts of the plate is consistent; and adjust the squeegee to India Edition angle and distance, power on the test. After the test proofs are qualified, they can be formally printed by signing the workshop supervisor and the customer. Here is a brief introduction to the printing process using a combination gravure printer as an example: