Gravure printing machine from the technical point of view of the gravure printing machine to buy gravure printing machine


Published on:

2019-01-03

Abstract: Gravure press comparison - purchase - experience chapter: a brief analysis of the printing part of the gravure press and instructions on how to buy a gravure press. The following content is compiled by buy.com and provided for your reference. Gravure printing machine from the technical point of view of gravure printing machine gravure printing machine is mainly divided into three parts: the uncoiling part, the printing part, slitting and die-cutting part. In this article, we will first make a brief analysis of the printing part. The printing part is the core part of the gravure printing machine, completing the printing, overprinting and drying of various colors. 1, the number of color groups to choose gravure printing machine color group selection is very critical, which is mainly related to the leading products of cigarette packet printing enterprises and domestic cigarette decoration of the general environment

Gravure printing machine from the technical point of view of the gravure printing machine to buy gravure printing machine
Abstract: Gravure press comparison - purchase - experience chapter: a brief analysis of the printing part of the gravure press and instructions on how to buy a gravure press. The following content is compiled by Buy.com and provided for your reference.

Gravure printing machine from the technical point of view of the gravure printing machine to buy gravure printing machine

Gravure printing presses are divided into three main parts: the uncoiling part, the printing part, and the slitting and die-cutting part. In this article, we will first make a brief analysis of the printing part.

The printing part is the core part of the gravure printing machine, completing the printing, overprinting and drying of various colors.

1、Number of color groups selection

Gravure printing machine color group number selection is very critical, which is mainly related to the leading products of cigarette packet printing enterprises and the general environment of domestic cigarette decoration. Domestic cigarette packet design patterns and processes are more complex, the first few years of domestic cigarette packet printing equipment to 6 and 7 colors, mainly 8 colors in the past two years, the basic configuration model includes a full-page color, four general colors, two spot colors and a varnishing unit. The number of color groups is not the more the better, the more the number of color groups in the control of paper (wikipedia) deformation, the difficulty of each color overprinting, etc., and the capital investment will also increase. However, if the number of color groups is too small, it is difficult to reflect the advantages of gravure printing machine fast and efficient and once formed, so users must choose according to their own needs and combined with future development planning. Although the unit gravure machine manufacturers are committed to increasing the number of units in the future, but when increasing the number of units again, not only is the investment larger, but also due to the technical upgrade of the gravure machine and gravure machine installation location and space and other factors, will be subject to many restrictions.

2、Selection of printing width

The requirements for printing width vary greatly from manufacturer to manufacturer, and the wider the width, the higher the requirements for paper, and the greater the impact on overprinting. Cigarette packet printing equipment is more suitable for the width of the main 650mm and 820mm two. Previously, printers basically choose the former, in terms of nesting, plate making, plate installation, die-cutting cylinder, paper specifications are more economical. In the layout can be lined up soft package small box 6 rows of 4 columns, hard package small box 6 rows of 2 columns, strip box 1 row of 2 columns, die-cutting cylinder 6 rows of 2 columns or 8 rows of 2 columns, the maximum paper width of 650mm, due to the smaller width, the printing process of paper deformation is smaller, very favorable to the product overprint. However, there is a critical problem, that is, in the printing of strip box products, the paper fiber direction perpendicular to the printing direction, for the current high-speed cigarette packaging machine, its packaging adaptability is poor, the appearance of poor molding, resulting in more quality problems. For this reason, many printers have to adopt the practice of printing only one at a time, which seriously affects the efficiency of the gravure printing machine.

In the past two years, the industry has basically reached a consensus that if printing strip boxes, it is best to choose a gravure printing machine with 820mm format, so that the strip boxes can be arranged in 1 row and 2 columns, 6 rows and 3 columns for hard package boxes, and 6 rows and 5 columns for soft package boxes. For high overprint accuracy requirements and the need to use a variety of printing processes for the product. It is recommended that as few rows as possible, generally 12 to 16 pieces for the more ideal number of typesetting, which can reduce the waste caused by paper deformation and multi-processing processes. If the inline die-cutting method, the layout can be free of this limitation.

3、Mounting method of printing plate cylinder

The mounting method of the printing plate cylinder has a great impact on the overprinting accuracy, printing flatness and runout of the printing plate cylinder, and plays a key role in whether the printing equipment can operate at high speed. In the past, the mounting method was mostly mechanical, but there were two problems: inconsistent installation tightness and easy loosening, which could easily cause a drop in overprint accuracy under high-speed operation. Now the installation of the printing plate cylinder is basically changed to pneumatic locking, locking force consistent, and not easy to loosen, suitable for high-speed printing.

4、Overprint control

Register accuracy is the core index of gravure printing machine, which plays a key role in product quality and loss control. Previously, gravure presses were only capable of longitudinal automatic register control, and the register marks were generally 4mm*4mm or 4mm*6mm squares or rectangles, and the adjustment of horizontal register was mainly done manually. At present, both horizontal and vertical register are automatically adjusted, so that the horizontal register mark must be required. There are two main types of such control, one is to add a register mark to control the horizontal register on the original basis, so that each color group must be controlled with two scanning positions. Another is to change the overprint mark to a triangle, using the hypotenuse of the triangle as the control point, the length of the right-angled side of the triangle is 4 to 8 mm, which is the control mode currently used more. In the adjustment of the register deviation, before mainly by adjusting the position of the plate cylinder relative to the paper to achieve the alignment of each color register, the current main use of adjusting the paper relative to the position of the plate cylinder, this way without changing the running speed of the plate cylinder, which is conducive to high-speed operation of the register adjustment, and the adjustment accuracy is easy to control, high register accuracy. In order to ensure the high quality requirements of the print, gravure printing machine overprint accuracy should be controlled within ± 0.10mm.

5、Drying method

In the past, gravure printing machine mainly used hot air drying method, mainly for solvent-based ink, but now gravure printing uses many kinds of ink and varnish, such as alcohol-soluble ink, water-based ink and varnish, UV ink and varnish, etc., only relying on hot air drying method can no longer solve the problem. At present, the drying method of infrared heating wind is mainly used, especially after a large number of water-based inks are used, the hot air drying device with large air volume becomes the basic configuration. Hot air drying device has the use of electric heating, there are also steam heating, electric heating method on the electric capacity needs a lot, about 150 kVA, if the power needs to increase capacity, and ready-made steam pipeline, you can directly use the steam heating method. At the same time, the number of equipment using UV curing method is also increasing, but there are still some problems with the ink and process, I believe that in the near future, UV curing method will also become the standard configuration.

6、Ink circulation system

Gravure printing ink, especially the deployment of spot-color ink, if two or more of the linking material resin compatibility is poor, it is easy to precipitation. In addition, the larger particles of gold and silver ink is also very easy to precipitation. Therefore, the circulation of the ink is essential. Ink circulation system must have the following functions: stirring ink, to avoid precipitation or ratio change; normal transport of ink, the transport process is not easy to produce bubbles, precipitation and splash; filter ink, the mesh of the filter should be about 120 mesh; solvent supplement function, to ensure that the ink viscosity appropriate.

7、Electrostatic ink transfer device

The disadvantage of gravure printing process is that the mesh tuning printing is very limited, especially in the printing of full-page transition network or local level effect, the accuracy to reach 175 lines / inch is very difficult, and small dots are easy to lose, the printing effect is very rough. Electrostatic ink transfer device can significantly improve the situation, it is in contact with the electrostatic pressure roller and paper conductive surface, paper and plate cylinder between the formation of high pressure electrostatic area, under the action of electrostatic, the ink from the plate cylinder in the cavity and evenly transferred to the paper surface, the ink transfer rate to or close to 100%. There is no need for each color group is equipped with electrostatic ink transfer device, generally a production line with four color group configuration is sufficient. Should be reserved in each color group on the installation position, printing color group position changes, electrostatic ink transfer device can be converted between color groups. Now, the role of domestic electrostatic ink transfer device has been very satisfactory, and can also be interchangeable with foreign devices, the price is only about 1/5 of imported devices.

8、Shaftless drive mode

Gravure presses generally use universal shaft drive, but the linear speed of the plate cylinder in the drive varies greatly, even affecting the overprinting accuracy. In the past two years, shaftless transmission technology has been developed rapidly, high-grade gravure machine basically use shaftless transmission, greatly improving the multi-color gravure machine transmission and overprinting accuracy, and can fundamentally realize the single-unit transmission control, is the main way of multi-color unit transmission in the future. Now more shaftless drive mode is used for each unit is directly driven by a DC motor, and then centralized control is realized on the basis of sub-unit control, for example, the speed of a single unit can be changed to control the single-color unit that is not in use to stop running, in order to reduce wear and energy consumption, and it is also essential to improve the accuracy of overprinting under high-speed operation. c

9、Tension control mode

Previously, the whole gravure press production line used only one set of tension control system, which was placed behind the last printing unit and adjusted the tension of the whole production line by controlling the relative speed difference between the paper feed speed and paper output speed. The range of tension variation is large, generally above 50 Newton, plus it achieves overprinting by adjusting the position of the printing plate cylinder, and the tension variation between each color group is even larger, so the stability of overprinting between colors is also very poor. Nowadays, it is basically changed to the tension control of color groups, and the tension control of the whole production line is dispersed to each color group, which largely reduces the range of tension variation, and generally the tension variation of each color group is about 5 Newton, which lays a good foundation for accurate overprinting. In the whole production line, the tension value of each color group should be as consistent as possible, generally according to the different paper, should choose a fixed value between 200 to 300 Newton, so that the printing process of the paper tension uniformity, and to a certain extent to reduce paper deformation.

10、Online quality monitoring

Online quality monitoring can be divided into three levels: online partial overprint monitoring, online product pattern monitoring and alarm, and online product pattern and ink color monitoring. Online local overprint monitoring is to pass the local overprint cross line or key fine pattern on the printing web through the digital camera, and then magnify the processing, generally 15-20 times, and synchronize the tracking. The operator can monitor the overprinting effect of the whole printing surface, and find problems and make adjustments in time. Online partial overprint monitoring is the most basic and necessary online quality monitoring mode, generally installed in one or two parts, the price of a system is about 50,000 to 80,000 yuan. Online product pattern monitoring and alarm is the sample sheet pattern into the computer, the same is the online print scanning, and compare the print pattern position with the sample sheet pattern position change, if there is a change that alarm, to remind the operator to adjust, and online products to mark or reject. This approach is now more widely used, and the price of a system is about 800,000 RMB. Online product pattern and ink color monitoring is based on the second online quality monitoring method, adding automatic adjustment of equipment and control of ink color, this method is used very little, mainly used in the printing industry, because the cost of monitoring equipment is relatively high.