Fine corrugated cardboard offset printing technology application

The characteristics of direct offset printing on fine corrugated cardboard

The direct offset printing technology of micro-corrugated board has gradually matured with the development of new fine and fine corrugated cardboard, special blankets and inks. Offset printing is the most popular and most mature printing method in China, and the quality of printing is also widely recognized. We believe that this direct offset printing method will become a very strong marketing tool in China. However, this new technology is only applicable to fine corrugated cardboard, especially G-type and F-type micro-corrugated cardboard.

The direct printing of micro-corrugated cardboard has the advantages of high production efficiency, low material consumption, low production cost, large product specifications, wide application range, high strength of the carton, neat appearance, and favorable environmental protection, and is a main process for corrugated box printing. The global demand for this technology shows that it is increasingly accepted in offset printing and flexo printing. Even in the future, the print quality that can not be achieved by flexographic printing can be achieved in offset printing, because the letterpress printing has its limitations after all. The packaging industry continues to increase its print quality requirements. The packaging design further promotes the offset printing of fine corrugated cardboard in the performance of excellent product transportation and external packaging.

Pre-printing can be processed by printing methods such as flexo and gravure. This method can guarantee high printing quality and overprinting accuracy. The printing speed is fast and the yield is high. However, after printing, the web must be re-formed to form a roll print and then finely corrugated. The corrugated paperboard production line is used for the cutting of fine-cutting corrugated cardboard production lines. The cutting precision and requirements are therefore high, and this method is suitable for large quantities of products in the same batch. If the product variety is large, the batch size of the single product is not large. When using preprints, it is not ideal.

Corrugated carton industry in China is familiar with printing methods for printing corrugated and flexo-printed corrugated cartons, and the application is common, but it is relatively unfamiliar to preprinting and offset printing. However, with the gradual perfection of the market and the gradual maturity of the process, direct offset printing is based on the excellent quality of its own four-color printing, coupled with the development of modern offset printing technology of the manufacturer in this field, direct offset printing of fine corrugated cardboard shows a good market expectation.

Offset printing can enter the field of direct color printing on micro-corrugated board, benefiting from the following two aspects: First, the successful development of new micro-corrugated cardboard has made important contributions to the realization of direct offset printing on micro-corrugated cardboard. Secondly, offset printing meets the need for the development of color printing on fine corrugated paperboard, while fine corrugated cardboard is also suitable for direct printing on offset printing presses, in which G-type and F-type micro-corrugated cardboard have good stability and can also be printed in the field. In particular, offset presses are now equipped with offset printing units and are no longer used for printing. This is also more conducive to the development of direct offset printing on fine corrugated board.

Fine corrugated paper advantage of direct offset printing

With the development of direct-printing micro-corrugated board technology with offset printing, it will replace flexo printing in certain areas of corrugated box printing. Figure 1 is a comparison of the quality and cost distribution of offset corrugated printing with direct offset printing of micro-corrugated cardboard with flexo and offset printing. As can be seen from Figure 1, direct offset printing is better than flexo printing and the cost is lower. In terms of quality and cost, direct offset printing is between flexo printing and offset printing between two processing methods.

Relative to the traditional color flexo printing process, direct offset printing has obvious advantages

â–  Excellent print quality, prints fine text and lines.
â–  Low printing cost, offset printing using conventional PS plates, low cost, and high standardization of offsets helps reduce production costs.
â–  Various special promotional information can improve printability.
â–  Short setup and adjustment time, more economical for short version.
Compared with the processing method of offsetting with cotton paper and corrugated paper, the advantages of direct printing of fine corrugated cardboard are:
â–  Eliminating the cost of counterfeiting, the reduction in the number of processes leads to a corresponding reduction in material waste.
â–  The amount of paper is small.
â–  Because there is no need for another work process, the entire printing process time is relatively shortened and the efficiency is improved.

Problems and Solutions of Direct Corrugation of Micro-Corrugated Cardboard

The first thing that should be considered in the direct offset printing of micro-corrugated cardboard is the uneven surface of micro-corrugated cardboard. Unlike the printing of plain paperboard, the printing of fine corrugated cardboard must take place on uneven surfaces caused by corrugations and troughs. Offset printing on uneven substrates is difficult to perform, and printing quality is difficult to guarantee.

Substrate irregularities are a major challenge for fine corrugated board printing. The structure that the printer must handle the grooves and backs corresponds to the three-dimensional plate structure. Another difficulty lies in the fact that in fact the pressure required for the transfer of ink from the blanket to the corrugated paper is 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 weaken the structure and stability of the fine corrugated cardboard. This condition is the starting point for direct offset printing on fine corrugated cardboard. Many corrugated paper suppliers already provide the necessary material quality to accommodate non-stop printing.

The blankets needed for direct offset printing on micro-corrugated cardboard should be quite flexible. 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 groove. In order to maintain the color of the fine corrugated cardboard and the stability of the box type. Due to the optimization of the blanket, the ink can be well transferred to the highest quality of fine corrugated board printing.

Another problem is that the printing needs to transfer ink to the substrate with a certain pressure. In order to make the corrugated paper surface completely printable relative to the corrugation trough, the printing pressure must be higher than the printing pressure required for the smooth surface material, which inevitably generates a greater pressure at the crest of the micro-corrugated cardboard. , resulting in a decrease in the strength of the fine corrugated cardboard.

In order to solve the above problems, a special rubber blanket was developed. The elasticity of the blanket was smooth. Therefore, even if a large amount of pressure is applied during printing, the pressure at the crest of the paperboard will not be greatly increased. This avoids the damage of the fine corrugated cardboard and ensures that the overprinting accuracy and the fine corrugated cardboard stacking are smooth. The emergence of such blankets has greatly promoted the development of direct offset printing of fine corrugated board.

One of the most important conditions for the direct offset printing of fine corrugated board is to optimize the ink so that the effect of the washboard is minimized. The development of the blanket is mainly for the printing of fine corrugated cardboard, compensating the change in the printing pressure between the back and the groove of the fine corrugated cardboard by its high compressibility. However, the remaining pressure difference can still cause the ridges and recesses to expand and ink overprint to varying degrees. This needs to be compensated by the ink during the printing of fine corrugated cardboard. Print tests show that optimizing the ink significantly reduces the washboard effect. It prints in a wider color gamut and has been shown to be best suited for the printing of fine corrugated cardboard.

The successful application of the direct printing of micro-corrugated board technology by the offset press has made corrugated box packaging and printing enter a new stage of development. Due to the high quality and low cost of direct offset printing on micro-corrugated cardboard, 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 direct-printing micro-corrugated cardboard technology by offset presses, and also established new printing quality standards for corrugated paper box packaging. Of course, this does not mean that only offset printing will have the future of direct printing of fine corrugated cardboard. Thick cardboard boxes are still printed mainly by flexo printing. Many long-lasting cardboard boxes will still use flexo printing because of their relatively simple shapes and design patterns. Similarly, high-quality corrugated cartons will also be offset-printed and then processed. Despite all kinds of restrictions, direct-printing micro-corrugated cardboard offset printing currently occupies a certain market share and will continue to grow.

Indirect offset printing of fine corrugated cardboard

The indirect printing method of the fine corrugated cardboard is to print the cardboard surface paper first, and then paste the printed tissue paper to the corrugated paper. Offset printing uses conventional PS plates. Since the resolution of PS plates is relatively high, very fine printing patterns can be printed. At present, most of the high-grade corrugated boxes used in sales packaging in China are offset printing. In the corrugated box production process, offset printing is a kind of pre-printing method. That is, the first paper is printed on the front and then on the fine corrugated cardboard. It is not much different from the ordinary offset printing process, and it is not considered in this case. Only Simple analysis of its main features. Offset printing corrugated boxes have the following characteristics:

â–  Easy plate making, regular plate making for PS plate.
â–  Can finish the surface, such as laminating, polishing and so on.
â–  High printing costs.
â–  It is not suitable to use paperboard linkage production line. It is only suitable for single-faced corrugating machine and the production efficiency is low.
â–  Limited format, generally smaller than flexo print carton format.
â–  The printing products are very fine, and the number of screens can reach 150-200 lines/inch. The printing quality is relatively stable.
â–  Due to more post-processes, the strength of the board is reduced.
â–  Ink generally contains benzene, which has some pollution.

Direct printing on micro-corrugated cardboard, due to the effect of printing pressure, the strength of the carton will certainly decline, which is a major drawback of direct printing of micro-corrugated cardboard. The effect of printing on the strength of micro-corrugated board is mainly reflected in the printed area and the printed position. In general, as the printing area increases, the board strength decreases proportionately. The total printing is reduced by about 40%; transverse belt printing is reduced by about 35% at the center width of 50mm; about 30% at the width of the lower edge of 50mm; and the width of printing is reduced by about 30% at the upper and lower sides by 50mm; on the side and end of the carton. The central part is reduced by about 5% in vertical printing of 50mm.

With the continuous development of printing technology and process, the printing of fine corrugated cardboard will further develop. There will be more competition between several printing methods of micro-corrugated cardboard, and this competition will also promote the development of micro-corrugated cardboard printing. Several printing methods of micro-corrugated cardboard will occupy a certain market with its own characteristics.