Basic principles of the most popular flexible corr

2022-09-22
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The basic principle of flexographic corrugated paper printing

flexographic printing is a kind of relief printing process, which uses a flexographic plate and transfers ink through a grain transfer ink roller. The printing plates it uses are all embossed with graphics and texts. During printing, a certain thickness of ink layer is evenly coated on the image and text part of the printing plate by the embossing roller, and then lechal is more suitable for the blind. Under the pressure of the embossing cylinder, the ink layer of the image and text part is transferred to the surface of the substrate to form a clear image and text. The inking mechanism of flexible corrugated paper printing machine is usually a two roller inking mechanism

(1) two roll inking system

the printing plate cylinder rotates on the side of the impression cylinder, and the linear speed is consistent with that of the impression cylinder. When the machine stops for a short time, the ink bucket roller and the wrinkle roller based on a large number of experiments move up and separate from the plate cylinder, while the ink bucket roller and the wrinkle roller continue to rotate in order to homogenize the ink and keep the ink on the wrinkle roller from drying. The ink bucket roll rotates on the side of the stripper roll, and its tangent speed is lower than that of the stripper roll. The purpose is to control the ink volume and prevent ink splashing. Most of the printing machines used for printing corrugated paper are combined flexographic printing machines. The units of this flexographic printing machine are independent and arranged in a horizontal straight line

(2) flexible plate material

flexible plate material can be divided into rubber plate and photosensitive resin plate: the plate material of rubber plate is natural rubber or synthetic rubber; There are many kinds of photosensitive resin plates, which can be divided into liquid photosensitive resin plates and solid photosensitive resin plates according to their forms. Seamless printing plate is made of plate-shaped solid photosensitive resin plate

the photosensitive resin flexo consists of a protective layer, an anti sticking layer, a photosensitive layer, an adhesive layer and a subbase

the function of protective layer and anti sticking layer is to protect the photosensitive layer; The role of the subbase is to support the photosensitive layer; The function of the adhesive layer is to closely bond the photosensitive layer and the subbase together. The photosensitive layer is the main body of the printing plate. After exposure and development, it is a flexible embossing plate. The photosensitive layer is mainly composed of high elastic unsaturated rubber polymer, photoinitiator, crosslinker, sensitizer, thermal inhibitor, etc

it should be noted that due to the rough surface of corrugated paper, thick flexible plates must be selected; If you want to print some high-grade products, you must choose a flexible version with high resolution and small scalability

(3) ink transfer roller

ink transfer roller is the core of flexographic printing machine. It has many types, such as chrome plated roller, ceramic roller, etc. no matter which one, its structure, function and principle are the same

1) structure of ink transfer roller. The surface of the ink transfer roller is provided with a concave groove line for controlling the ink transfer volume during printing. The surface grooves of the ink transfer roller are regularly arranged to form concave holes. The ink transfer performance of the ink transfer roller is related to the number of grooves, the shape of holes, and the arrangement of holes

① number of lines: the distribution number of points per cm in the direction with the shortest distance between points is the number of lines, which indicates the distribution density of points

the number of lines of the roller affects its ink transfer capacity: the larger the number of lines, the greater the hole density, the smaller the hole volume, and the less the ink transfer capacity. Corrugated paper printing generally uses a low line number of corrugated rollers (generally less than 65 lines/inch)

② acupoint shape: generally refers to the three-dimensional shape of acupoints. There are many kinds of cave shapes, which are basically divided into nuclear cone shape and pyramid shape

2) characteristics of the ink transfer roller

① the holes on the ink transfer roller are the same size and evenly distributed, which can effectively transfer and control the ink volume, making the ink film thickness uniform and the ink volume consistent. And it is less difficult to ink due to the poor viscosity of the printing ink

② with high precision, the corrugated roller can ensure the transmission of ink under a small pressure and reduce the ink blotting phenomenon at the edges of graphics and texts. The inking is uniform, and it is not easy to have a stiff edge

③ ink transfer by roller is adopted, and ink transfer failures such as ghosting or bar rarely occur, and ink flying rarely occurs in high-speed printing

④ the ink volume is easy to adjust by using the corrugated roller inking device. The thickness of the transferred ink layer is relatively thin, and the tensile test, pressure test, peel test, tear test and shear bending test are often uniform, making dot color printing possible, and the ink film density is consistent from the minimum point to the field

⑤ the corrugated roller has high durability and corrosion resistance. According to the selection and measurement range of materials, especially the application of laser engraving ceramic corrugated roller, the service life of the corrugated roller and the stability of ink transfer are greatly improved

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