In recent years, the competition in the packaging market has become increasingly fierce. People are increasingly demanding packaging, and corrugated carton packaging is also consolidating the original protection products and transport packaging functions that are convenient for storage and transportation. It also needs to gradually improve sales that attract customers and stimulate purchase desires. Function, the two closely combined. As a result, corrugated carton pre-printing methods followed the trend.
Corrugated box pre-printing: demanding
As the name suggests, corrugated box preprinting is to print the relevant pattern in advance before the corrugated board is finished. Specifically, before the production of corrugated paperboard, first the roll paper is printed on the roll paper, and the printed roll paper is then sent to the face paper station of the corrugated board production equipment, and the corrugated board is processed, and then After the process of forming. In fact, the pre-printing of corrugated cartons that appears to be uncomplicated has various “demanding requirements” for many production elements.
1. Paper requirements
The printed surface of the coated white paper has a good color expression, but in the process of bonding through the corrugated high temperature drying tunnel, the paint will have varying degrees of change, directly affect the color surface pattern effect; hanging pulp white paper, although able to meet the corrugated The requirements of the high-temperature drying tunnel bonding process, but its rough surface, will make the printing pattern lose dot, false, poor visibility, while the ink consumption is large. Practice has proved that good preprinted paper should be white cardboard. It can not only fully express the color of printed patterns, but also can withstand the test of the bonding process of corrugated high-temperature drying tunnels.
2. Ink requirements
Preprinting has special requirements on the heat resistance and rubbing resistance of the ink.
Preprinted inks are based on water-based inks, which are non-toxic, odorless, easy to operate, and environmentally friendly. Because the preprinted face paper should be flattened and passed through the drying section in the corrugated board production line, the required water-based ink should be high-temperature resistant and wear-resistant.
3. Requirements for printing equipment
At present, preprinting methods include gravure printing and flexo printing.
The device used for gravure preprinting is mainly a web gravure printing machine, and the gravure printing machine of the gravure type has a relatively high level of technology due to a more reasonable layout, so it is used in preprinting.
The equipment used for flexo preprinting is mainly a roll-to-roll flexo printing machine. Among them, the satellite flexographic printing machine can meet the requirement of the width and repeat length, and the constant temperature of the central impression cylinder can ensure the stability of the printing material. , used more in preprints.
4. Requirements for corrugated board production line
In the preprinting process, the pattern must be printed first, and then corrugated composite bonding and cutting should be performed on the corrugated board production line. In this process, the pattern factor must be carefully treated. In the past, computer-cutting on corrugated paperboard production lines was mostly transversal to fixed length. Therefore, a photoelectric tracking cross-cutting control system was installed on the cross-cutting knife, and the cross-cut mark on the printed pattern of corrugated cardboard was identified by the photo-electric eye. The time when the cut mark reaches the photoelectric eye is transmitted to the control computer, and the cutting time of the cross knife is controlled by the control computer so as to accurately cut the corrugated cardboard at the boundary of the pattern. At present, cross-cutting machine manufacturers at home and abroad can easily add this function, and the cross-cutting accuracy can be controlled within 1mm.
In addition, the pre-printed tissue paper is subjected to sizing and veneering steps on corrugated paperboard production lines and several other cardboard layers, and then it is re-entered into a double-sided machine for flattening, heating, cutting, printing and corrugating production lines. Heating the plate for a long time can cause the print pattern to pull. At present, the domestic paper packaging industry has achieved certain breakthroughs in this area and can solve this problem well.
Corrugated carton flexo preprinted: good and bad
In the United States in the 1980s, Coca-Cola and Pepsi used a large number of carton boxes as the outer packaging of beverage bottles. Thus, the rising demand at one time led to the popularity of the production method of printing patterns on wide webs using the flexo printing technology. But until now, the quality of most flexographic preprinted cartons is still in the middle and low grades, and the printing speed needs to be improved.
The carton is processed by flexo preprinting. The general production speed is 100 to 300 meters per minute, and the advantages and disadvantages are obvious.
The advantages of flexo preprinting
1. Fast and efficient. The speed of satellite type flexographic printing presses is usually 200 to 400 m/min, which can be matched with high-speed corrugated cardboard production lines.
2. The printing quality is high. Uniform printing pressure, free from the influence of corrugation, good printing effect; printing color number up to 8 sets, 150 lines/inch plate making, delicate dots and colorful colors; fine pattern, reasonable selection in plate, color separation, network cable When the angle, dots, and inks are used correctly, the print quality can be comparable to gravure printing.
3. Low cost. The low cost of flexo printing has reached a broad consensus in foreign countries, but it is presented differently in China. It is mainly because most of the flexographic printing presses and plates used in the country are imported, so the cost is high. However, as China's printing equipment manufacturers accelerate the development of flexo printing equipment and plates, and their localized production and sales in China, it is believed that in the near future, the production cost of flexographic preprinting will gradually decrease.
4. The printing adjustment time is short and the loss of printed materials is low. The color drying distance of the satellite type flexographic printing press is 550-950mm, which is much smaller than that of the gravure printing press. Therefore, less raw materials are consumed for adjusting the overprinting. At the same time, there are few overprint changes during the entire printing process, and the reject rate is low. .
5. In the corrugated board production line, the retanning and bonding of the paper and the corrugated board can improve and improve the strength and the stamping strength of the corrugated cardboard box.
6. A wide range of printing materials, cardboard for a larger range of quantitative, paper in the range of 80 ~ 400g/m2 can be printed.
Disadvantages of flexo preprinting
1. Due to the flexo itself, the range of tones that can be copied when copying a continuous original is between 8% and 85%. More than 85% of the area coverage of the dot area will produce a merging stage, resulting in dark sticing and burying into a solid, levelless place; in areas below 8%, the printing is easy to lose, and the printing outlets are easy to expand, so the flexo printing cannot Ideally restore patterns with rich colors and levels.
2. From the perspective of printing screens, the highest number of lines for offset and gravure is higher than for flexo. The ideal number of screens for flexo printing is generally less than 150L/in. Over 175L/in will increase the difficulty of flexo platemaking, and will also reduce the life of the plate.
3. Do not use thin lines and small text. Because the flexographic plate will be deformed during the printing process, the thin lines and text are easily deformed. In practical production, rough lines should be used as much as possible, and the color of decorative lines and main lines should be greater.
4. Large equipment investment. The price of a satellite-type flexo printing machine with a printing width of 1.2m is more than 10 million yuan.
5. Flexo preprinting is suitable for long-lived jobs, and the customer's face is too narrow.
Since the Deyang Daily Printing Factory introduced the first roll-to-roll web printing machine in China, the application of corrugated box pre-printing technology has been gradually carried out in various parts of China. At present, domestic paper packaging companies are preprinting equipment, water-based inks, and materials. Other areas have also achieved great success one after another. It is believed that as people's requirements for packaging increase, the pre-printing technology of corrugated cartons flexo printing will also be well-established in the Chinese paper packaging industry.
