Today, with the rapid development of the market economy, the packaging of commodities is becoming more and more important. It has become a consensus that exquisite packaging can improve the taste and sales price of commodities. Therefore, the manufacturers of commodities have increasingly higher requirements on the quality of packaging and printing.
Large-area spot color is a kind of contrast and rendering method commonly used in product packaging design. It is an important form to reflect the image of commodity shelves, and it is also the difficulty of printing and copying and the key point of quality control.
In China, offset printing is one of the main ways of paper packaging printing. The process is mature and can replicate very fine products. It can cater to the mass consumer psychology of the Chinese market, so the penetration rate is very high. Sheet-fed gravure printing is a printing method that has emerged in recent years. It is unique in spot color and solid printing, and is quite flexible to use. According to business needs, our factory purchased the sheet-fed gravure printing machine produced by Beijing Zhenhengli Printing Machinery Co., Ltd., and used it with the original offset printing machine, and achieved good results in packaging printing.
This article intends to analyze the large-area field packaging and printing, and analyze which equipment is more suitable for the single-sheet gravure printing machine and the domestic two-color offset printing machine.
Due to the characteristics of the machine itself, the operation of the single concave machine is very simple. The paper conveying part and the receiving part are the same as the offset printing machine. Generally, anyone who can operate the offset printing machine can operate the single concave machine without special training. The main difference between sheet-fed gravure printing and sheet-fed offset printing is the printing plate and ink used.
From the point of view of the printing plate, at first glance, it seems that the cost of gravure printing is relatively high, but it is not necessarily the case. Because the durability of gravure printing plates is very high, the general platemaker's commitment is: at least one million prints, and the volume of packaging prints is generally relatively large, and often requires repeated printing. So for a long time, when printing large-area field packaging products, the difference between the plate-making costs of gravure printing and offset printing is not very big. In addition, the produced gravure printing plate rarely causes print quality fluctuations due to the influence of external factors during the on-press printing process, and the quality is very stable. The single-gravure machine is very convenient to install the plate. After the normal printing, as long as the ink viscosity is not too much deviation, the entire printing process will be very smooth, and the printed products can easily maintain the same ink color.
Judging from the inks used, gravure inks cost about the same as ordinary resin offset inks, but gravure inks have the characteristics of low viscosity and good fluidity. Due to the large amount of volatile organic solvents used, the printing ink layer is The infrared part of the drying part of the gravure printing machine can quickly dry under the irradiation, there is no problem of sticking of the printed matter, and the next color can be printed immediately after printing one color, or transferred to the next process for post-printing processing.
The offset printing process, if you use ordinary resin-based ink, the ink can not be completely dried on the printing press, you need to spray powder on the paper collection part to prevent the printed matter from sticking. A slight error in powder control will cause the printed matter to become dirty, leading to an increase in scrap rate and a decrease in production efficiency. Since the oxidative polymerization and drying of common resin inks takes a long time, the printed products cannot be immediately subjected to secondary printing or post-press processing. They need to be left for a period of time to be fully dried. Although the use of UV ink can eliminate various disadvantages in the drying process of offset printing products, the printing cost will increase a lot. Even if the cost of installing a UV curing device is not considered, only the cost of ink, UV ink is about 10 times that of ordinary offset printing ink.
The large-area field printed by the single concave machine has bright colors, saturated hue, and thick ink layer. If the single concave machine is used for water-based glazing or UV glazing, the color effect is better and the wear resistance of the ink layer will be better. . The large area of ​​the field is printed by the offset printing process. If ordinary resin-based ink is used, it is usually printed twice to barely meet the customer's requirements. However, the ink layer is thick and it is difficult to dry. As a result, the surface of the ink layer is rough and dull, and the brightness after glazing is difficult to meet the requirements. If anodized aluminum hot stamping is required in the subsequent process, it will cause difficulties in hot stamping. A large amount of powder spraying not only affects the printing quality, but also adds difficulties to the subsequent operations. In addition, the use of two-color offset printing is also prone to ink color differences, solid color lines and other problems.
The ink supply of Zhenhenli single concave machine uses an uninterrupted circulating ink supply system. As long as the upper viscosity of the ink is controlled, the viscosity of the ink will not be affected by external environmental factors during the printing of the entire batch of products. The ink color of the whole batch of products is stable before and after.
Due to the problem of water-ink balance in offset printing, it is difficult to achieve consistent ink color between the front and back prints. After all, the ink level and the water level are changing all the time. Especially when printing after shutdown, the ink color changes more, and the paper must be added frequently to adjust the ink color. With the gravure printing machine, there is no need to add the plate paper, and then stop printing before printing, you can immediately get the same ink color as the previous print. In this way, the pass rate of printed products will be greatly improved compared with offset printing, reducing paper consumption and naturally saving printing costs.
From the perspective of applicable paper, the single concave machine has wider adaptability, while the offset printing machine is not suitable for printing non-absorbent materials, such as gold and silver cardboard. Because the surface of gold and silver cardboard is very smooth, ordinary offset printing ink cannot adhere well on the surface, and the ink layer is prone to become thin and uneven, and the printed ink is difficult to dry; even if it is dried, the problem of ink layer peeling is difficult avoid.
With the fierce market competition, consumers are more and more picky about commodities, and the packaging of commodities has to be developed towards high-end to improve the competitiveness of commodities. The application ratio of gold and silver cardboard and glass cardboard is constantly increasing. The offset printing process has been difficult to adapt. Printing high-grade gold and silver cardboard packaging should be the first gravure printing.
From the above rough comparison, it can be seen that when printing large-area field packaging products, the overall cost of using a single concave machine and a domestic two-color offset printing machine is similar, but in terms of printing effect and production efficiency, a single concave machine is better than offset printing. The opportunity is better.
The following is a comparative example of a cigarette pack printing example to analyze the combined process of full offset printing and offset printing, see attached table.
Comparison of large field printing
Print: "Specially Made Good Cigarettes" cigarette packs of Jiangxi Gannan Tobacco Factory;
Models: Beiren J2204 offset printing machine, Zhen Henry four-color, single-color single concave machine;
Operator configuration: 3 domestic two-color offset presses and 2 sheet-fed gravure presses;
Printing materials: 250g /? White cardboard;
Printed sheet specifications: 540mm × 740mm, 15 small puzzles;
Printing process: full offset printing, combination of offset printing and gravure printing;
Ink: standard magenta, yellow, black ink, spot color red ink, coffee spot color ink, thermochromic yellow ink;
Glazing: The printed products are partially glazed with a glazing area of ​​0.294? / Sheet.
Through comparative analysis, the advantages of the offset-gravure combination process over the full offset printing process are summarized as follows:
1. The labor intensity is reduced, and the operation of the single concave machine is simple. The domestic two-color offset printing machine requires 3 people to operate, while the single concave machine only needs 2 people to operate. Based on the monthly salary of 1,500 yuan per operator, saving an operator will undoubtedly bring additional benefits to the enterprise.
2. Production efficiency is improved. It takes 15 minutes for the single-gravure machine to install the plate and 10 minutes for the proofreading, and then adjust the viscosity of the circulating ink in 5 minutes, and then it can be produced normally, which is 15% faster than the preparation of the offset printing. After normal printing, it can be continuously printed at the speed of 6000 sheets / hour. The single concave machine does not have problems such as cleaning the blanket, removing paper wool and white spots. The printing time saved per shift is 1.5 hours, and the total time saved when installing the plate is 1.7 to 2 hours. Each shift can increase the output by 6000 × 2 = 12000 (sheets), and one printed sheet is 15 pieces.
3. The waiting time of the next process is greatly shortened, the unit time can be used to increase the capacity to develop more new business, save time for equipment maintenance, save overtime costs during the peak season, shorten the product cycle, and further improve the competitiveness of enterprises in the market .
4. Single concave machine does not need to spray powder, the ink is dried by infrared ray, the required electricity cost is basically the same as the cost of powder material for offset printing. After water-based glazing with a single concave machine, the smoothness and abrasion resistance of the printed surface are improved.
5. Since the gravure ink layer is dried instantly, there is no sticky (backprint) phenomenon, so the waste products are reduced.
After converting the special-made Jiapin cigarette pack to the single-gravure machine to print the spot color red and coffee spot color, there was no sticky and dirty product, and the defective rate was greatly reduced, thereby increasing the economic benefit.
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