Analysis of the purchase of cigarette marking machine from the perspective of printing technology
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In the past two years, the domestic tobacco industry has undergone great changes. The restructuring and integration of cigarette companies, especially the increase in the concentration of cigarette brands, means that the production of single-brand and single-brand cigarettes will be greatly increased, which requires cigarette pack printing enterprises to quickly provide large quantities of cigarette packages. Therefore, cigarette package printing enterprises must have a certain scale of production and production capacity.
At present, the effective combination of multiple materials and various printing processes has become the development trend of cigarette package printing. Gravure printing has many advantages, such as high production efficiency, good color consistency, good adaptability of printing materials, excellent performance in field, spot color, gold (silver) ink printing, etc., to meet the strict requirements of cigarette pack quality. Gravure printing machines have become a popular choice for cigarette printing companies. In addition, the quality inspection of cigarette package prints will be further reflected in the printing odor, packaging machine adaptability, color loss, environmental protection, etc., in these aspects, gravure is also more advantageous than other printing processes. Therefore, the purchase of gravure printing equipment has become a topic of great concern to cigarette printing companies. The author below talks about the introduction of the web gravure printing machine, hoping to help the cigarette package printing enterprises.
The gravure printing machine is mainly divided into three parts: the unwinding part, the printing part, the slitting and the die cutting part. This article first briefly analyzes the printed part.
The printed part is the core part of the gravure printing machine, which completes printing, overprinting and drying of various colors.
1. Select the number of color groups.
The selection of the color number of the gravure printing machine is very important, which is mainly related to the leading products of the cigarette printing enterprise and the large environment of domestic cigarette decoration. The pattern and process of domestic cigarette package design is more complicated. In the past few years, domestic cigarette package printing equipment is mainly composed of 6 colors and 7 colors. In the past two years, it mainly consists of 8 colors. The basic configuration mode includes one full color and four colors. Universal color, two spot colors and a coater. The number of color groups is not as good as possible. The more the number of color groups, the more difficult it is to control paper deformation and color overprinting, and the capital investment will increase. However, if the number of color groups is too small, it is difficult to reflect the advantages of fast and efficient gravure printing and one-time molding, so users must choose according to their own needs and future development plans. Although the manufacturer of the unit type gravure printing machine promises to increase the unit in the future, it will not only invest more when the unit is added, but also will be affected by factors such as the technical upgrade of the gravure press and the installation position and space of the gravure press. limit.
2, the choice of printing format.
Manufacturers have very different requirements for the printing format. The wider the width, the higher the requirements for paper and the greater the impact on overprinting. The most suitable format for the cigarette printing device is 650mm and 820mm. In the past, the printing factory basically chose the former, and it was economical in terms of typesetting, plate making, plate installation, die-cutting cylinder, and paper specifications. In the typesetting, you can arrange soft packs of 6 rows and 4 columns, hard packs of 6 rows and 2 columns, 1 box of 2 rows, 3 rows of 2 rows or 8 rows of 2 rows of die-cutting rollers, and the maximum width of the paper is 650mm. Smaller, the paper is less deformed during the printing process, which is very advantageous for the overprinting of the product. However, there is a key problem, that is, when printing the strip box product, the direction of the paper fiber is perpendicular to the printing direction. For the current high-speed cigarette packaging machine, the packaging adaptability is poor, the appearance molding degree is poor, and the quality problem is caused. many. To this end, many printing companies have to adopt only one print at a time, which seriously affects the efficiency of the gravure press.
In the past two years, the industry has basically reached a consensus. If you print a box, it is best to choose a 820mm format gravure printing machine. In this way, the box can be arranged in 1 row and 2 columns, and the hard box is 6 rows and 3 columns. Box 6 rows and 5 columns. For high overprint accuracy requirements and products that require multiple printing processes. It is recommended to have as few rows as possible, generally 12 to 16 pieces are ideal for typesetting, which can reduce waste caused by paper deformation and multi-process. If online die cutting is used, typesetting can be excluded from this limitation.
3. How to install the plate cylinder.
The mounting method of the plate cylinder has a great influence on the overprinting precision, the printing flatness and the beating of the plate cylinder, and plays a key role in the high speed operation of the printing equipment. In the past, it was mostly a mechanical installation method, but it had two problems: the installation tightness was inconsistent and easy to loose, and in the case of high-speed operation, the overprinting accuracy was liable to decrease. Nowadays, the installation method of the plate cylinder is basically changed to pneumatic locking, the locking force is consistent, and it is not easy to loose, which is suitable for high speed printing.
4. Overprint control.
Overprinting accuracy is the core indicator of the gravure press and plays a key role in product quality and loss control. In the past, the gravure printing machine was only capable of longitudinal automatic registration control. The overprinting mark was generally 4 mm * 4 mm or 4 mm * 6 mm square or rectangular, and the lateral registration adjustment was mainly done by hand. At present, both horizontal and vertical registrations are automatically adjusted, which requires the need for horizontal overprint marks. There are two main types of control. One is to add an overprint mark on the original basis to control the lateral overprint, so that each color The group must be controlled with two scanning positions. Another is to change the overprint mark to a triangle, and use the oblique side of the triangle as the control point. The length of the right side of the triangle is 4-8 mm, which is the control mode that is currently used. In the adjustment of the overprint deviation, the alignment of the color registration is mainly achieved by adjusting the position of the plate cylinder relative to the paper. Currently, the position of the paper relative to the plate cylinder is mainly adjusted, which does not change the operation of the plate cylinder. The speed is favorable for overprint adjustment under high-speed operation, and the adjustment precision is easy to control, and the overprinting precision is high. In order to ensure the high quality requirements of the printed matter, the overprinting accuracy of the gravure printing machine should be controlled within ±0.10 mm.
5. Drying method.
In the past, gravure printing machines mainly used hot air drying methods, mainly for solvent-based inks, but now there are many types of inks and varnishes used in gravure printing, such as alcohol-soluble inks, water-based inks and varnishes, UV inks and varnishes, etc., only relying on hot air drying methods. Can't solve the problem. At present, the drying method of infrared heating wind is mainly used, especially after a large amount of water-based ink is used, a hot air drying device with a large air volume becomes a basic configuration. The hot air drying device is electrically heated or steamed. The electric heating method has a large demand for electric capacity, which is about 150kVA. If the electric power needs to be increased and there is a ready-made steam pipe, steam heating can be directly used. the way. At the same time, the number of devices using UV curing is also increasing, but there are still some problems in ink and process. It is believed that in the near future, UV curing will become a standard configuration.
6. Ink circulation system.
Gravure inks, especially formulated spot color inks, are prone to precipitation if the compatibility of two or more of the binder resins is poor. In addition, gold and silver inks with larger particles are also prone to precipitation. Therefore, the circulation of the ink is crucial. The ink circulation system must have the following functions: stirring the ink to avoid precipitation or ratio change; normally conveying the ink, not easily generating bubbles, sedimentation and splash during the conveying process; filtering the ink, the mesh of the filter should be about 120 mesh; Solvent replenishment function to ensure proper ink viscosity.
7. Electrostatic ink transfer device.
The disadvantage of the gravure printing process is that the screen printing is greatly limited, especially when printing a full-page transition net or a partial layer effect, the precision is up to 175 lines/inch, and the small dots are easily lost, and the printing effect is very rough. The electrostatic ink transfer device can significantly improve the situation. It forms a high-voltage electrostatic region between the conductive surface of the electrostatic pressure roller and the paper, and the paper and the plate cylinder. Under the action of static electricity, the ink is removed from the cell of the plate cylinder. The medium is sucked out and evenly transferred to the surface of the paper, and the ink transfer rate reaches or approaches 100%. It is not necessary to configure an electrostatic ink transfer device for each color group. Generally, it is sufficient to have four color group configurations for one production line. The mounting position should be reserved on each color group, and the electrostatic ink transfer device can be switched between the color groups when the position of the printing color group changes. Nowadays, the role of the domestic electrostatic ink transfer device has been very satisfactory, and it can also be exchanged with foreign devices, and the price is only about 1/5 of the imported device.
8, no shaft drive mode.
The gravure printing machine generally adopts the universal joint shaft transmission, but the linear speed of the printing plate cylinder in the transmission changes greatly, and even affects the overprinting precision. In the past two years, the shaftless transmission technology has been rapidly developed. The high-grade gravure printing machine basically adopts the shaftless transmission, which greatly improves the precision of the transmission and overprinting of the multicolor gravure printing machine, and can fundamentally realize the transmission control of the single unit. It is the main way to drive multi-color units in the future. Nowadays, more shaftless transmission modes are adopted, that is, each unit is directly driven by a DC motor, and then centralized control is realized on the basis of the control of the unit, for example, the speed change of the single unit can be realized, and the monochrome that is not used is controlled. The unit is shut down to reduce wear and energy consumption, and it is also critical to improve the accuracy of overprinting at high speeds.
9, tension control mode.
Previously, the entire gravure printing machine production line used only one set of tension control system, placed behind the last printing unit, and adjusted the tension of the entire production line by controlling the relative speed difference between the paper feed speed and the paper exit speed. The tension varies widely, generally above 50 Newtons. In addition, by adjusting the position of the plate cylinder to achieve overprinting, the tension between the color groups changes more, so the stability of overprinting between colors is also poor. Now basically change to the tension control of the color separation group, the tension control of the whole production line is dispersed to each color group, which greatly reduces the variation range of the tension. Generally, the tension change of each color group is about 5 Newtons. Precise overprinting lays a good foundation. In the whole production line, the tension values of each color group should be as consistent as possible. Generally, according to the difference of paper, a fixed value between 200 and 300 Newtons should be selected to make the paper tension uniform during printing and reduce to some extent. Paper is deformed.
10. Online quality monitoring.
Online quality monitoring can be divided into three levels: online partial overprint monitoring, pattern monitoring and alarming of online products, online product patterning and ink color monitoring. Online partial overprint monitoring is to apply a partial overprint crosshair or key fine pattern on the printing surface through a digital camera, and then perform amplification processing, generally 15 to 20 times magnification, and synchronous tracking. The operator can monitor the overprinting effect of the entire printing format and find problems in time. Online partial overprint monitoring is the most basic and necessary online quality monitoring mode. Generally, one or two parts are installed. The price of a system is about 50,000-80,000 yuan. Pattern monitoring and alarming of online products means that the sample pattern is input into the computer, and the online print is scanned, and the position of the printed matter and the position of the sample pattern are compared. If there is a change, the alarm is alerted to the operator to adjust and online. Products are marked or rejected. This method is now widely used, and the price of a system is about 800,000 yuan. On-line product pattern and ink color monitoring is based on the second online quality monitoring method, which increases the automatic adjustment of the device and the control of the ink color. This method is used very rarely, mainly in the printing industry because of monitoring. The cost of equipment is relatively high.