Characteristic Analysis of Corrugated Offset Printing
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First, the characteristics of direct offset printing of corrugated cardboard
Corrugated board direct offset technology is maturing with the development of new fine corrugated board, special blankets and inks. Offset printing is the most popular and most mature printing method in China. The printing quality is widely recognized by everyone. It is believed that this direct printing method will become a very powerful processing method in the market. However, this new technology is currently only applicable to fine corrugated cardboard, especially G-type and F-type corrugated cardboard.
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 for corrugated box printing. The global demand for this technology shows that it is becoming more accepted in offset and flexo printing. Even in the future, the printing quality that can't be achieved by flexo printing can be achieved in offset printing, because the relief printing has its limitations. The packaging industry continues to grow in print quality requirements. The packaging design further promotes the offset printing of corrugated cardboard in the performance of excellent product transportation and external packaging.
Pre-printing can be processed by printing methods such as flexo printing and gravure printing. This method can ensure high printing quality and overprinting precision, fast printing speed and high output, but it needs to be re-rolled to form a roll print after printing, and then corrugated cardboard. The production line is re-corrugated, so the cutting precision and requirements of the cutting device on the corrugated board production line are high, and the method is suitable for the same batch of products. If the product variety is large, and the batch of the single variety is not large, Pre-printing is not ideal.
China's corrugated box industry is already familiar with the first printing and then two types of corrugated box processing methods, and the application is also very common, but it is relatively unfamiliar for pre-printing and offset printing. However, with the gradual improvement of the market and the gradual maturity of the process, direct offset printing has a good market by direct offset printing of corrugated cardboard by virtue of the excellent quality of its four-color printing and the development of modern offset printing technology by the manufacturer in this field. prospect.
Offset printing can benefit from the following two aspects of direct color printing in corrugated board:
First of all, the successful development of the new corrugated board has made an important contribution to the direct offset printing of corrugated board.
Secondly, offset printing caters to the needs of color printing development of corrugated board, and fine corrugated board is also suitable for direct printing by offset printing machine. The stability of G-type and F-type corrugated board is good, and it can also be printed in the field. In particular, the offset press is now equipped with a flexo coating unit, which is no longer just for printing. This is also more conducive to the development of direct offset printing of corrugated cardboard.
Second, the advantages of direct offset printing of corrugated cardboard
With the development of offset printing 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 a corrugated paper directly printed with corrugated paper and offset printing and offset printing. As can be seen from Figure 1, the direct offset printing quality is better than the flexo printing, and the cost is relatively low. The combination of quality and cost seems to be that the direct offset printing is between flexo and offset printing between the two processing methods.
Direct offset printing has obvious advantages over traditional color flexo printing:
1 Excellent printing quality, printing extremely fine text and lines.
2 printing cost is low, the cost of offset printing using conventional PS plate making is low, and the high standardization of offset printing helps to reduce production costs.
3 various special promotional information can improve printing performance.
4 installed version of the machine is short, the short version is more economical.
Compared with the processing method of offset paper with corrugated paper after offset printing, the advantages of offset printing directly on corrugated cardboard are as follows:
1 The cost of confrontation is saved, and the reduction of the process reduces the waste of materials.
2 paper is added less
3 Since the additional working process is not required, the entire printing processing time is relatively shortened, and the efficiency is improved.
Third, the problem of direct offset printing of corrugated cardboard and its solutions
Corrugated board direct offset printing should first consider the problem of uneven surface of corrugated board. Unlike ordinary board printing, corrugated board printing must be performed on uneven surfaces caused by corrugated waves and troughs. Offset printing is difficult for uneven printing, and printing quality is difficult to guarantee.
The unevenness of the substrate is a major challenge for corrugated board printing. The printing press must handle the structure of the grooves and the ridges corresponding to the slab structure. Another difficulty is that in fact the transfer of ink from the blanket to the corrugated paper requires a certain contact pressure in order to achieve a clear image in the grooved portion. This pressure is higher than the effective printing pressure on the smooth surface of the ridge, and it does not impair the structure and stability of the corrugated board. 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 blanket required for direct offset printing of corrugated cardboard should have a fairly good elasticity. It enables the printing process to use the highest printing pressure without causing too much pressure on the spine. This avoids excessive compression of the grooves. Thereby maintaining the color of the corrugated cardboard and the stability of the box type. Thanks to the optimization of the blanket, the ink can be transferred very well to the highest quality of corrugated board printing.
Another problem is that the printing needs to transfer the ink to the substrate with a certain pressure. In order to completely print the image of the corrugated paper surface relative to the corrugated trough, the printing pressure must be higher than the printing pressure required for the flat surface material, which inevitably generates a large pressure at the peak of the corrugated cardboard. This results in a decrease in the strength of the corrugated board.
In order to solve the above problems, a special blanket has been developed, and the elastic curve of the blanket is gentle. Therefore, even if a large pressure is applied during printing, the pressure is not greatly increased at the peak of the cardboard, which avoids the damage of the strength of the corrugated cardboard and ensures accurate overprinting and flattening of the corrugated cardboard. The emergence of such blankets has greatly promoted the development of direct offset printing of corrugated cardboard.
One of the most important conditions for direct offset printing of corrugated board is to optimize the ink to minimize the effect of the washboard. The development of the blanket was mainly for corrugated board printing, and its high compressibility compensated for changes in the printing pressure between the corrugated cardboard back and the groove. However, the remaining pressure difference can still cause ridge and recess dot enlargement and ink overprinting to varying degrees. This needs to be compensated by ink when printing corrugated cardboard. Printing tests have shown that optimizing the ink significantly reduces the effect of the washboard. It is printed in a wider color gamut and has proven to be the most suitable for corrugated board printing.
The successful application of offset printing machine direct printing corrugated board technology has made corrugated box packaging printing enter a new stage of development. Due to the high quality and low cost of direct offset printing on corrugated board, 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 also promoted the rise of offset printing machine direct printing corrugated board technology, and also established new printing quality standards for corrugated box packaging. Of course, this does not mean that only offset printing has the future of direct printing of corrugated cardboard. Thick cardboard boxes are still based on direct printing of flexo printing. Many thin cardboard boxes are still used in the long version because of the simple shape and design pattern. Similarly, high-quality corrugated boxes will also be used for offset printing and then the processing of the enamel. Despite various restrictions, offset printing of corrugated cardboard currently has a certain market share and will continue to grow.
Fourth, indirect offset printing of corrugated cardboard
The indirect printing method of corrugated cardboard is to first print the carton paper, and then paste the printed tissue paper onto the corrugated paper. Offset printing uses a conventional PS board. Since the resolution of the PS version is relatively high, it is possible to print very fine printed patterns. At present, most of the high-grade corrugated boxes used for selling packaging in China are offset printing. In the production process of corrugated boxes, offset printing is a pre-printing method, that is, printing on the opposite paper first, and then on the corrugated board. It is not much different from the general offset printing process, so it is not considered here. Its main features are simple analysis.
Offset printing corrugated boxes have the following characteristics:
1 plate making is easy, for the PS version of the regular plate.
2 can be surface finishing, such as film, glazing and so on.
3 printing costs are high.
4 It is not suitable for the use of cardboard linkage production line, only suitable for single-face corrugating machine, and the production efficiency is low.
The 5 sheets are limited and generally smaller than the flexo box.
6 printing products are very fine, the number of screen lines can reach 150-200 lines / inch. Printing quality is relatively stable.
7 The strength of the paperboard is reduced due to the large number of post-processes.
8 inks generally contain benzene, which has some pollution.
Direct printing on corrugated cardboard, due to the pressure of printing, the strength of the carton will certainly decline, which is a major drawback of direct printing of corrugated cardboard. The effect of printing on the strength of corrugated board is mainly reflected in the printed area and the printed position. In general, as the printed area increases, the strength of the paperboard decreases proportionally. Full printing is reduced by about 40%; horizontal strip printing is reduced by about 35% at a center width of 50mm; by about 30% at a width of 50mm at the lower edge; by about 37% at a width of 50mm on both sides; and on the side and end of the carton The central part is longitudinally printed by 50mm and is reduced by about 5%.
With the continuous development of printing technology and technology, the printing of corrugated cardboard will be further developed. There will be more competition between several printing methods for corrugated cardboard, and this competition also promotes the development of corrugated board printing. Several printing methods of corrugated cardboard will occupy a certain market by virtue of their own characteristics.