Analysis of the characteristics of corrugated cardboard offset printing
1. Characteristics of corrugated cardboard direct offset printing
Corrugated cardboard direct offset printing technology has gradually matured with the development of new fine corrugated cardboard, special blankets and inks. Offset printing is the most widely used and most mature printing method in China, and the printing quality is widely recognized by everyone. I believe this direct printing method of offset printing will become a very powerful processing method in China. But at present, this new technology is only applicable to fine corrugated board, especially G and F corrugated board.
Corrugated cardboard direct printing has the advantages of high production efficiency, low material consumption, low production cost, large product specifications, wide application range, high carton strength, neat appearance, and environmental protection. It is the main process of corrugated cardboard printing. The global demand for this technology shows that it is gradually being accepted more in offset and flexo printing. Even in the future, the printing quality that cannot be achieved by flexographic printing can be used in offset printing, because letterpress printing has its limitations after all. The packaging industry's requirements for printing quality continue to grow. The performance of packaging design in the transportation of excellent products and external packaging further promotes the offset printing of corrugated cardboard.
Pre-printing can be processed by printing methods such as flexo and gravure printing. This method can ensure high printing quality and overprint accuracy. The printing speed is fast and the output is high. The production line is re-corrugated, so the cutting precision and requirements of the cutting device on the corrugated cardboard production line are relatively high, and this method is suitable for a large number of products in the same batch. If there are many product varieties and the single-type batch is not large, Using pre-printing is not ideal.
The corrugated box industry in our country is already familiar with the two methods of corrugated box printing, printing first and then direct mounting and flexographic printing, and its application is also very common, but it is relatively unfamiliar with pre-printing and offset printing. However, with the gradual improvement of the market and the gradual maturity of the process, direct offset printing Relying on the excellent quality of its four-color printing and the manufacturer's research and development of modern offset printing technology in this field, corrugated cardboard direct offset printing presents a good market prospect.
Offset printing can enter the field of corrugated cardboard direct color printing due to the following two aspects:
First of all, the successful development of new corrugated paperboard has made an important contribution to the realization of direct offset printing of corrugated paperboard.
Secondly, offset printing meets the needs of the development of color printing on corrugated cardboard, and fine corrugated cardboard is also very suitable for direct printing by offset presses, of which G and F corrugated cardboard have good stability and can also be printed on the spot. Especially now the offset press is also equipped with a flexographic coating unit, which is no longer just for printing. This also contributes to the development of corrugated cardboard direct offset printing.
Second, the advantages of corrugated cardboard direct offset printing
With the development of offset printing direct corrugated board technology, it will replace flexo printing in certain areas of corrugated box printing. Figure 1 is a comparison of the quality and cost distribution of corrugated paperboard directly printed with offset printing, flexo printing and offset printing followed by corrugated board printing. As can be seen from Figure 1, the printing quality of direct offset printing is better than that of flexo printing, and the cost is relatively low. In terms of quality and cost, direct offset printing is between flexo printing and first offset printing between two processing methods.
Figure 1 Comparison of cost and quality of the three methods Compared with the traditional color flexo printing process, direct offset printing has obvious advantages:
â‘ Excellent printing quality, can print very fine characters and lines.
â‘¡The printing cost is low, the offset printing adopts the conventional PS plate making cost is low, the high standardization of offset printing helps to reduce the production cost.
â‘¢ Various special promotional information can improve the printing performance.
â‘£The time for installing and adjusting the machine is short, and the short version is more economical.
Compared with the processing method of cotton paper offset printing and corrugated paper mounting, the advantages of offset printing directly corrugated cardboard are:
â‘ The cost of mounting is eliminated, and the reduction of the process reduces the waste of materials accordingly.
â‘¡The amount of paper added is relatively small. â‘¢Since no additional work process is required, the entire printing processing time is relatively shortened, and the efficiency is improved.
3. The problems and solutions of corrugated cardboard direct offset printing
Corrugated cardboard direct offset printing should first consider the problem of uneven surface of corrugated cardboard. Unlike ordinary cardboard printing, corrugated cardboard printing must be performed on uneven surfaces caused by corrugated peaks and troughs. Offset printing is difficult to print on uneven substrates, and it is difficult to guarantee the printing quality.
The unevenness of the substrate is a major challenge for corrugated cardboard printing. The printing machine must deal with the structure composed of grooves and ridges corresponding to the structure of the three-dimensional plate. Another difficulty lies in the fact that ink transfer from blanket to corrugated paper requires a certain contact pressure in order to achieve a clear image even in the grooved part. This pressure is higher than the effective printing pressure on the smooth paper of the ridge, and it will not weaken the structure and stability of the corrugated cardboard. This condition is the starting point for direct offset printing of corrugated cardboard. Many corrugated paper suppliers have provided the necessary material quality to accommodate uninterrupted printing.
The blankets required for direct offset printing of corrugated cardboard should have fairly good elasticity. It enables the printing process to use the highest printing pressure without causing too much back pressure increase. This avoids excessive compression of the groove. So as to maintain the stability of the corrugated cardboard color and box shape. Due to the optimization of the blanket, the ink can be transferred well to the highest quality of corrugated cardboard printing.
Another problem is: In printing, the ink needs to be transferred to the substrate through a certain pressure. In order for the corrugated paper surface to be completely printed with respect to the corrugated wave valley, the printing pressure must be higher than the printing pressure required for the flat surface material, which will inevitably produce a large pressure at the corrugated cardboard wave crest, As a result, the strength of the corrugated cardboard is reduced.
In order to solve the above-mentioned problems, a special rubber cloth was developed, and the elastic curve of this rubber cloth is very gentle. Therefore, even if a large pressure is applied during printing, the pressure will not be greatly increased at the crest of the cardboard, which avoids the damage of the strength of the corrugated cardboard, and ensures that the overprinting is accurate and the corrugated cardboard is stacked flat. The appearance of this blanket greatly promoted the development of corrugated cardboard direct offset printing.
One of the most important conditions for corrugated cardboard direct offset printing is to optimize the ink so as to minimize the effect of the washboard. The development of blankets is mainly for corrugated cardboard printing, through its high compressibility to compensate for the change in printing pressure between the corrugated cardboard spine and groove. However, the remaining pressure difference can still cause the dots of the ridges and recesses to expand and the ink to overprint to varying degrees. This needs to be compensated by ink during corrugated cardboard printing. Printing tests showed that optimizing the ink significantly reduced the washboard effect. It completes printing in a wider color gamut and proves to be the most suitable for corrugated cardboard printing.
The successful application of the technology of corrugated board printing directly on offset presses has made corrugated box packaging printing enter a new stage of development. Due to the high quality and low cost of corrugated cardboard direct offset printing, the printing and packaging industry can no longer ignore this technology.
The design concept and market demand for displaying products and promoting products through storage and transportation packaging have also promoted the rise of direct printing corrugated cardboard technology for offset presses, and also established a new printing quality standard for the field of corrugated box packaging. Of course, this does not mean that only offset printing has the future of direct printing of corrugated cardboard. Thick carton is still mainly based on flexographic direct printing, and many thin carton long-form jobs will still use flexo printing due to the relatively simple shape and design patterns. Similarly, high-quality corrugated boxes will also use offset printing first, and then the mounting method. Despite various restrictions, offset direct printing corrugated board currently has a certain market share and will continue to grow.
4. Indirect offset printing of corrugated cardboard
The indirect printing method of corrugated board is to print carton facial paper first, and then mount the printed facial paper on corrugated paper. The conventional PS board is used for offset printing. Due to the high resolution of the PS version, very fine printing patterns can be printed. At present, most of the high-end corrugated boxes used for sales and packaging in China are printed by offset printing. In the production process of corrugated boxes, offset printing is a pre-printing method, that is, printing on the facing paper first and then laminating on the corrugated cardboard. It is not much different from the general offset printing process, so it is not considered here. Do a simple analysis of its main features.
Corrugated cardboard boxes with offset printing have the following characteristics:
â‘ Easy plate making, it is the conventional plate making of PS version.
â‘¡Surface finishing can be carried out, such as coating and glazing.
â‘¢ High printing cost.
â‘£It is not suitable for the use of cardboard linkage production line, only suitable for single-sided corrugated machine, and the production efficiency is low.
⑤ The format is limited, generally smaller than that of flexo carton.
â‘¥The printed products are very fine, and the number of screen lines can reach 150-200 lines / inch. The printing quality is relatively stable.
⑦Because of more post-processes, the strength of the cardboard is reduced.
⑧Ink generally contains benzene, which has some pollution.
Direct printing on corrugated cardboard, due to the effect of printing pressure, the strength of the carton will definitely decline, which is a major disadvantage of direct printing of corrugated cardboard. The effect of printing on the strength of corrugated cardboard is mainly reflected in the area and location of printing. Generally speaking, as the printing area increases, the strength of the cardboard decreases proportionally. Full printing is about 40% down; horizontal band printing is about 35% down at the center width 50mm; about 30% down at the bottom width 50mm; about 37% down at the upper and lower sides of the 50mm width; and at the side and end of the carton The central part of the vertical printing of 50mm is about 5% down.
With the continuous development of printing technology and process, the printing of corrugated cardboard will be further developed. There will also be more competition among several printing methods of corrugated board, and this competition will also promote the development of corrugated board printing. Several printing methods of corrugated cardboard will occupy a certain market with their own characteristics.
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