Application Analysis of Combination Printing in Screen Printing (I)

A printing method has its own special advantages and also has its own insufficiencies. This is a defect that can improve the quality of printed products and create new printing effects. In order to make up for the inadequacies of various printing methods, people are constantly improving equipment and researching new technologies and developing new materials. After research, it has been found that the advantages and disadvantages displayed by different printing methods are sometimes complementary. If they can be combined and applied, it is possible to learn from each other. In view of this, printers are dedicated to finding a printing method that can obtain a variety of printing process effects on the same product. Therefore, in recent years, a wide variety of printing processes have been widely used in online printing in combination printing. Compression printing is becoming more and more popular because people use printing and finishing as a holistic solution. The development of numerous related technologies has also made combination printing not only a reality, but also a good marketability and economy.

In recent years, the development speed of combination printing has been rapid, and a printing press can be arbitrarily combined into several different printing processing methods, so that products that can be printed and processed on multiple machines can be completed at one time. Practice has proved that the combination printing can indeed be as expected, not only can play a complementary role, but also can create new printing effects and expand the scope of printing.

First, the main features and types of combination printing

Combined printing is a production line consisting of various types of printing and finishing machines. Combination printing can use flexographic, silk screen, gravure, offset printing and other printing processes. Combination printing units are commonly screen printing, flexo printing, gravure, embossing and hot stamping printing units. The main purpose of combination printing is to make up for the defects of various printing methods and improve the quality of printing. The second is to add decoration and artistic effects to the printed matter so as to make the printed material unique. With the ever-growing prosperity of the printing market, modern people are increasingly demanding print products. Many new processing technologies continue to emerge, and printers are also trying their best to find a printing method that can achieve multiple technological effects on the same product. On the other hand, all kinds of printing processes have their own inherent advantages and disadvantages. The best characteristics of several printing methods are brought into full play and a perfect production line with comprehensive performance is the purpose and significance of combination printing. The current common printing methods are:

(1) Indirect stamping. Also known as letterpress offset printing, it is a printing cylinder that retains a rotary embossing in a letterpress offset printing system, a blanket cylinder in a rotary offset printing press, and an ink inking device thereof.

(2) Indirect gravure. Including letterpress gravure and gravure offset printing. Relief gravure is mostly used for multicolor stitch printing, so it is also called gravure gravure printing and is mainly used for printing of securities to meet the basic requirements of anti-counterfeiting.

(3) Embossing. In fact, it cannot be considered as a complete printing method. It does not use ink, but uses a specially-engraved concave stencil and inverted convex stencil, and uses an embossing machine to press out a concave-convex graphic on a surface of a printed matter or substrate that has already been printed.

(4) adhesive convex printing. Full use of offset printing has a good reduction, can realistically reflect the original features of the scene, soft colors, rich layers, strong sense of three-dimensional, clear text and the advantages of letterpress printing with bright colors, high gloss, real ink layer The advantages of thick and full, reflect the characteristics of the two printing methods on one printing surface at the same time, so that the print screen has a unique style.

(5) Cable embossed embossed printing. It is somewhat similar to embossing. Instead of a printing color plate, a pattern embossed and multi-layered embossed stencil is formed by embossing the surface of a stamp having a metallic luster texture such as electro-aluminum, gold-silver cardboard, or the like. It not only makes the prints rich in three-dimensional, but also due to the different angles and levels of the track to produce light scattering, thus showing a strange and colorful dynamic visual effects, improving the decorative product.

(6) Combination of flexographic and rotary screen printing. Full use of screen printing printing ink layer thickness, the ink layer can be adjusted, etc., and then with the flexographic printing press printing, making its application in the field of packaging and anti-counterfeit printing more extensive and enhance the attractiveness of the product.

Second, the main equipment, materials and other technical issues

Although combined printing can overcome the deficiencies of various printing methods and improve the quality of printed products, due to the use of two or more printing methods for combination printing, there are many printing methods encountered in printing. problem. In other words, since combination printing is a complex of multiple printing processes, its operation must take into consideration the various suitability of each type of printing and the influence of each other. Therefore, the difficulty is relatively large and generally requires attention. The following points.

(1) Due to the difference in printing materials, the order of the various printing has a great difference. In order to ensure the quality of printed matter and adapt to the combination of printing processes required for various types of printed matter, it must be ensured that the sequence of the units used in the combined printing press has sufficient variability to accommodate the combination of printing processes required for various printed matters. For example, in the combined printing of screen printing and flexo printing, when printing a color printing screen, whether the printing machine set is placed before or after the flexographic printing unit, or even in the middle, involves the consideration of the printer configuration. Each unit should be a fixed or variable decision. In general, the hot stamping unit is placed at the end of the printing unit.

(2) Since the ink compositions used in different printing processes are different from each other, the inks produced by different companies are not compatible with each other, and incompatibilities may even occur between different product lines in the same manufacturing plant. Different technologies are supported by different chemical principles. The use of inks in two different systems thus creates problems with overprinting and adhesion. For example, silicon-free UV flexo inks often cause problems with poor overprint performance on silicon-containing screen printing inks. Therefore, prior to printing, ink compatibility tests should be conducted and the manufacturer should be informed of the ink's technical data. If there is no test or other conditions, the ink can be adjusted by the operator on the printing machine. In addition, inks are sometimes incompatible with other post-print finishing processes such as hot stamping, inkjet, and laser printing. Therefore, before using inks and other consumables, it is best to clearly understand the performance characteristics of each consumable by the manufacturer and supplier, so that when printing, it is easy to know how to overcome such failures.

(3) The color matching of the ink in the combined printing must be trained in regular color matching and equipped with advanced color matching equipment such as spectrophotometers. Practice has proved that when people who have not been trained in the normal color matching of the factory or those that lack advanced color matching spectrocolorimeters, the errors in the assigned colors are considerable. Because the ink of the same color adopts different printing processes, because the manufacturer usually chooses the pigments of different substrates, this means that the oil can adapt to different processes (such as the screen printing ink and the flexo ink when color matching), its color Problems such as saturation, printability, etc. often occur.

(4) On combination presses, the printing speed is always controlled by the slowest one of the units. Therefore, set the printing unit speed according to the printing requirements. For example, a hot stamping machine or a round screen printing machine, the speed of the flexo printer can reach 300 feet per minute when using UV ink, and the speed of the online stamping machine is only 100 feet per minute. It is impossible to reach 300 feet/minute.

(5) Great care must be taken to train the operator in various printing processes. Because different processes require different types of operating skills. Many aspects of skills training are necessary measures to ensure that operators have a variety of process operations and fully understand the technical parameters of various processes. When the printing factory first used the combined printing process, another training goal was to sell the factory's sales personnel. This was not only to enable them to deal with the customer's supply department, but also to learn to interact with the client's creative designers. In the final product design process, they work closely together.

(to be continued)