The development course and application of preprinting equipment

Pre-printing is the pre-printing of the desired pattern before making corrugated cardboard. Broadly speaking, according to the form of printing materials, it can be divided into sheetfed and web preprinted in two ways.

Sheet-fed preprinting is not only traditionally used for offset printing on single-carton face paper, but also uses a veneer machine to bond the good faced paper with corrugated paper and die-cut into various box shapes. Its main features are: exquisite printing, low plate-making cost, adaptability to different quantities of orders, but it also has the following deficiencies: slow production efficiency, low strength of the carton, a certain color for different batches and products of different manufacturers. Differences, etc.

The web preprinting is performed on the web and is still taken up as web material after printing; the web is then printed directly into the corrugated paper production line as corrugated cardboard and then cut into boxes. . Its main features are: beautiful printing, high production efficiency, the production of cardboard boxes with high strength and economy, more suitable for large quantities of products. The printing method can be divided into gravure and flexographic preprint.

With the growing maturity and expansion of the Chinese consumer market, traditional sheet-fed carton production methods have been difficult to meet the carton users' requirements for color boxes, and domestic gravure printing technology is quite mature. In 2001, the company's company was the first in China to launch the pre-printing gravure printing machine, which made our country's pre-printing technology have made great progress. Many well-known companies have adopted pre-printed packaging products such as Bright, Yili, Sanlu and Mengniu.

In the 1980s, due to the birth of the "Globally-unified logo and brand" theory, almost all multinational companies insisted that their branches and products sold around the world use completely consistent packaging. The meaning of "completely consistent" is that the structure, color, and content of the package are exactly the same. This “completely consistent” and high-quality printed images are used to attract the attention of customers and ensure the loyalty of customers to their brands. Therefore, these multinational companies require their packaging suppliers to provide corrugated cartons produced using pre-printing processes. Preprinting has become popular in the United States and Europe. In these developed countries, due to the more mature flexographic technology and higher requirements for environmental protection, preprinted equipment is mainly based on wide-format satellite flexographic printing presses. Its main features are: simple structure, higher printing speed, accurate color registration, and stronger adaptability to paper.

After the 1980s, China also imported some flexographic printing presses from abroad, but most of them were used in the field of flexible packaging (printing format, small repeat length). At the same time, due to the high prices of imported equipment and imperfections of related supporting equipment, wide satellites Flexographic printing presses are difficult to open in China; domestic manufacturers can only produce narrow-format flexographic printing presses (most of which are within 600mm), so flexographic preprinting has not been popularized in China. Two are using such imported equipment.

After the author's company launched gravure preprinting equipment, it did not stand still but continued to aim at the international advanced level to perfect the existing technology. In order to introduce advanced foreign equipment into the country, it is actively seeking cooperation with foreign manufacturers while developing its own equipment. Through cooperation with well-known foreign flexographic printing press manufacturers, we have produced wide-format satellite flexographic printing presses.

The satellite type flexo press is mainly composed of unwinding and inputting sections, printing sections, drying sections (dry and final drying in color), cooling sections, output and winding sections, and main transmission and control sections. The use of a common central impression cylinder for multiple printing units is a major feature of the satellite flexographic printing press. Printed materials are tightly applied to the center cylinder during the printing process, and the material removal path is shorter, so its overprint accuracy is higher. Flexo printing machine is more adaptable to printing materials. After simple adjustment of tension and other printing parameters, it can be used to print materials including paper, plastic film, aluminum foil, etc. to achieve a multi-purpose machine; satellite type flexographic printing machine is relatively intaglio. The simple structure of the printing press and the small number of control points make high-speed printing possible. The printing speed is between 250m/min and 350m/min. At the same time, the water-based ink used in the satellite flexo printing machine is more pollution-free and more environmentally friendly. The request.

For the printer, there is still a certain difference between flexo printing and offset printing and gravure printing. Therefore, we must pay attention to the technical support of the flexographic printing industry. We must not apply the experience of offset printing or gravure printing, and only understand and master the experience. The characteristics of flexographic technology can give full play to the strengths of flexographic printing. In the use of the need to pay attention to the following things.

In order to restore the rich levels and colors of the original in the printing plate, the plate should be as thin as 1.7mm and 1.14mm. Since the flexible plate will be distorted during printing, the use of fine lines and text should be minimized when designing the pattern.

In the case of a sufficient flexo printing machine, the same color screen and field version should be divided into two productions, because the screen printing needs thinner ink layer, while the field and line version require a thicker ink layer. However, under certain special circumstances, it is necessary to print the same color network lines and field images on the same plate. Under this circumstance, on the one hand, when choosing the anilox roller for printing, it is a trade-off consideration. Generally, it is necessary to give priority to the printing requirement of the cable screen version at the expense of the thickness of the ink layer in the field; on the other hand, it is necessary to master the difference in plate making. Exposure time to ensure the quality of the same plate version of the Internet and field parts. Therefore, several sets of anilox rollers should be used during the use to meet the printing needs of different products.

When choosing the ratio of the number of printing screens and the number of anilox roller screens, different proportions should be selected according to the degree of fineness of the product. The reason is that the most difficult problem to be solved when printing a gradation version with a flexographic printing press is to expand the network points and use a network with a higher number of screen lines. The roller, the ink layer is thinner, and the dot expansion and deformation are easier to control. For fine prints, the ratio is approximately 1:4.5 or 1:5. If it is found that the ink color is not strong enough during printing, a water-based ink with a higher color concentration may be used to ensure the quality of the printed product.

When doing equipment purchases, you should also pay attention to some auxiliary but crucial equipment, such as: high-precision plate sensors. If you use Shuanglian single-joint (dry one, two-up) printing plate in production, you can effectively save the cost and difficulty of plate making. But the premise is to have a high-precision paste machine, to ensure the overprint between the left and right color sequence. If there is no sticker machine or the precision of the sticker is not high, the two-up pattern needs to be made on the same sheet, that is, single-linked and double-linked, which increases the difficulty of plate making and plate-making costs.

With the domestic flexographic printing supporting technology, the domesticization of satellite flexographic printing equipment, the acceleration of integration with the world printing and packaging technology, and the deepening of people’s understanding of flexographic printing, it is believed that flexo printing will have a long way to go in China. development of. Although there are many advantages in flexographic printing, it will still be the case in which it coexists with offset printing and gravure printing. There is no replacement of who. For printing companies, only by fully understanding the various printing methods and the composition of their own products under the premise of choosing their own printing methods in order to obtain greater development.