Magnetic Printing Technology and Mechanical Exploration--Flexo Printing (I)

Third, flexographic printing

(a) Basic features of flexographic printing

Compared with other printing methods, the flexographic printing method has the main features of versatility and economy.

1. The printer's specifications are complete

Flexographic presses have many specifications and can be selected based on the intended use of the printed matter to make the use of substrates more extensive. It is generally possible to print strips that are as small as a few centimeters and substrates that are approximately several meters wide.

2. Wide applicability

Flexible printing plate making is convenient, the cost is low, the plate loading is convenient, the printing press has high speed, and the operation is simple; the printing materials are widely selected.

3. high productivity

According to production needs, it can be printed in front of multiple colors, but it can also print in front of and behind multiple colors at the same time; the printing plate has a high printing rate. All these have created favorable conditions for increasing productivity and reducing production costs.

(B) The basic principle of flexographic printing

The printing plate used for flexo printing has the same structure as that of a relief printing plate, in which the graphic part is raised (that is, the graphic text is higher than the non-graphical text part) in the same plane, and both are directly printed.

After the plate cylinder is loaded into the machine, a controlled thickness of ink is evenly coated on the plate graphic portion, and then the ink layer of the graphic portion is transferred under the effect of the printing pressure (given by the impression cylinder). The surface of the substrate, forming a clear printed copy of the text. Therefore, flexographic printing is a direct printing method using a rubber plate or photosensitive resin plate and a fast-drying liquid ink.

The transfer process of the flexographic printing ink is similar to that of the gravure printing: the transfer roller is directly placed in the ink tank. When the transfer roller rotates, the ink adhered to the surface is transferred to an anilox roller dedicated to transfer the ink, and then the web The roller coats the ink layer evenly on the surface of the printing plate graphic portion for printing at a controlled thickness. Since the ink does not need a uniform ink transfer process, the structure of the flexographic printing press is relatively simple. The principle of flexographic printing is shown in Figure 2-38.

(III) Types of Flexible Plates

Flexible printing plates are mainly non-photographic rubber plates, solid photopolymer plates and liquid photopolymer plates. Non-photographic rubber plates are mainly used for packaging and wallpaper printing. Solid photopolymer plates are mainly used for package printing, and liquid photopolymerization plates are mainly used. For newspapers and packaging printing.

(d) Flexo printing machine

1. Classification of flexographic printing presses

Most flexographic printers are multi-colored, ranging from two-color to eight-color. According to the arrangement of printing units, it can be divided into three types: co-embossing, cascaded and tandem.

(1) Co-imprinting Press Co-imprinting flexographic printing press, abbreviated as CI printing press, also known as satellite printing press. As shown in Figure 2-39.

The main features of a co-imprinting printing press are that each group of printing cylinders rotates together around a large-diameter central drum, and each center drum serves as an impression cylinder to complete the printing process.

In the entire process of co-imprinting printing machine, the substrate is covered on the surface of the impression cylinder, the flatness is good, the color registration between the color groups is high, and the printing is easy to stretch, wrinkled paper, plastic film, metal processing Color prints of paper and other materials. However, the distance between each printing unit of the co-imprinting printing press is short, the intermediate drying apparatus is simple, and the printing speed is relatively slow.

(2) Laminated printing presses As shown in Figure 2-40, the printing presses of the laminating printing press are independent from each other and form a printing unit and are stacked vertically. The distance between the printing units can be changed and the intermediate drying device can be conveniently placed.

The substrates of the laminating printing press are serially interposed between the impression cylinder and the plate cylinder of each printing unit, and the graphic transfer is completed by the printing pressure between the plate cylinder and the impression cylinder.

It is more convenient to exchange and install the plate cylinders of each printing unit of the stacking printing machine. When changing or installing plate cylinders, it does not affect the combined position of other printing units. It is easy to operate, with high mechanical precision and strong print adaptability.

Laminated printing machine overprint color number, and change the series of substrates, can be printed on one side, can also be double-sided printing, use more convenient and flexible.

(3) Tandem printing press A tandem type flexographic printing press, also known as a modular or seat type flexographic printing press, is similar in appearance to a combined gravure web press, as shown in Figure 2-41.

Each printing unit of the tandem printing press bears one color version of the printing, and the printing cylinder and the printing drum cooperate with each other to complete the printing process. Each printing unit is arranged in a horizontal line. Combination of multiple printing units can complete color printing. The tandem printer can not only print web material, but also sheet (single) material. Commonly used in printing stickers trademarks and news newspapers, sheet corrugated cardboard packaging materials, etc., have unique advantages. In addition, there are features such as good attachability and strong variability. For example, it can be matched with a group of gravure printing machines (a group or groups) according to needs, and die cutting is added at the rear part of the printing unit; the guide system of the additional web material, the ink circulation system, and the electrostatic treatment device for the plastic film are increased. The surface performance and decorative effect of the substrate can be printed, as shown in Figure 2-42.

(4) Broad shelf type flexo printing machine Co-imprinting printing machine narrow range of printing substrates; stacking printing machine can print wider width substrates, but can only print roll materials, and series The function of the printing press is more flexible. It can not only print the web material, but also print the single sheet material. The width of the printing web is also wide. However, there are also certain limits. If there is a wide range of substrates, only other printers can be used.

A wide-format bookshelf press is a special type of flexographic printing press.

The main feature of the wide-shelf bookshelf flexo printing machine is that it can print papers, plastic films, metal foils and other substrates of 1.6 to 4 meters or even more than 4 meters wide, and is generally equipped with automatic loading and unloading of substrates. s installation. Broad-width bookshelf flexo printing press can also be linked with laminating machine, folding machine, slitting machine, rewinding machine and other required machinery in series to process the substrate for post-processing, so that the substrate is suitable for the needs of commodity packaging.