Design and Optimization of the Production Process of Tobacco Roller Round Pressing
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With the smooth integration and development of tobacco industry brands, domestic high-speed cigarette packaging equipment has been put into production smoothly. In order to effectively improve production efficiency, all tobacco companies have accelerated the pace of technological transformation of cigarette packaging equipment, high-speed automatic packaging equipment and reel packaging equipment. The proportion of cigarette packaging materials is increasing, which has prompted more and more cigarette package printing enterprises to accelerate the investment in supporting production equipment, upgrade the production process, and improve process automation and product quality. Effectively reduce costs. The author of the Golden Mountain Gravure Printing Co., Ltd. is the configuration of the round paper rounding production line in this specific period through acquisition, joint research and development. In the application process of the round paper rounding production line, the author summarized the design and optimization of the printing, hot stamping, die cutting and automatic packaging of hard pack products, and will be divided into three parts to share with you. This paper first discusses the design and optimization of the circular press printing process for cigarette packets.
In recent years, more and more cigarette-pack printing companies in the industry have implemented the production method of web-printing offline round-pressing hot stamping die-cutting, on the seamless printing of individual products and the production process of paper sheets. Advantages and differences, etc., this article will not be described, mainly to propose the following points to discuss with peers.
About the printing and winding system
If the cigarette printing enterprise plans to adopt the web printing reel receiving production mode, it is best to purchase the active winding system when purchasing the gravure printing machine or the reel receiving device, which is compatible with the passive winding system. The main differences are as follows.
(1) The active winding is directly driven by the motor through the mechanical drive to rewind and rewind, generally adopting a two-axis (or three-axis) turret structure. Moreover, in order to ensure the tightness of the reel winding, the active winding must make the reel and the composite line speed the same, so it is required to have constant tension, constant line speed transmission, and constant power required to decrease the rotation speed as the winding diameter increases. Track. In addition, the active winding also requires the selection of a soft-characteristic motor whose transmission torque is inversely proportional to the rotational speed. At present, many AC torque motors and series-excited DC motors are used. Among them, the characteristics of the series-excited DC motor are similar to the active winding characteristics. The volume is of good quality.
(2) Passive winding is to press the two sides of the winding on the large-diameter surface roller by friction to drive the winding, so the linear speed of the winding roller should always be consistent with the surface roller. Because the paper for cigarettes is thicker, the tension between the inner and outer rings is difficult to be consistent. Therefore, seamless printing on the web can easily lead to changes in the repeat length of the printed pattern, especially for thin coated paper. If the overprinting is required, the overprinting is often performed. The loss is large.
For the original system directly equipped with the winding system, for example, the Bobst gravure printing machine is mostly equipped with the winding unit of Monomatic of France, and the general manufacturer will carry out detailed training. Sometimes the manufacturer will install other systems. For example, our Bobst gravure printing machine was originally equipped with a wire-cut flat unit, and later a Martin Winding System. The system adopts the active winding design, but in the debugging process, the printing registration has been very good and the material is very neat, but the paper roll in the post-process offline round-pressing hot stamping has a large running limit and an amazing scrap rate. Repeated inspection and analysis revealed that the reason was that the printing tension and the winding tension did not match well, and the repeat length of the printed pattern did not meet the requirements.
Confirmation of the repeat length of the printed pattern
Domestic cigarette packs are mainly concentrated in the two major groups of Yuncheng plate making and Seiko plate making. Some foreign cigarettes are designated by Indonesian manufacturers to use electronic engraving, laser engraving and other processes. After years of development, the quality of the plate rolls of various manufacturers is relatively stable. .
However, due to the different brands and driving methods of the gravure printing equipment of different cigarette printing enterprises, in the development of the traditional web printing and flattening process, and determining the printing circumference, most of the cigarette printing enterprises adopt the following methods.
(1) The diameter of the plate roll is increased by 0.02mm, which is more common in the traditional mechanical shaft driven gravure printing machine.
(2) The plate roller has no increment or small increment (for example, 0.01 mm), which is more common in electronic shaft driven gravure printing machines.
(3) The plate rolls are not incremented, and the printing pattern is enlarged in the circumferential direction as a whole.
Regardless of the method used, it is necessary to ensure that the error between the repeat length of the key color and the design circumference is ±0.15mm after the printing is wound, and the inner and outer rings are consistent. If the key color is not the first color, the diameter of each color is required. Recalculation, the individual color diameters may need to be decremented, which is beneficial to the registration of round and round processing.
Register cursor design
1. The design of the registration cursor in the paper direction (circumferential direction)
It should be determined according to the requirements of the gravure register registration system. It is consistent with the traditional web printing and flattening method. Most of them use triangle marks or wedge marks. Take the Bobst 820 gravure machine as an example. The standard wedge shape. The marking length is 10mm, and the short end of the wedge is 1mm. As shown in Fig. 1, the small wedge mark has a length of 6mm, which is mostly used for overprinting of soft packs.
For the hot-pressed and die-cut cigarette packages after the web printing, it is necessary to understand the working principle and requirements of the hot stamping machine and the die-cutting machine registration system, and to process the hot stamping and die-cutting after printing separately at the appropriate position of the paper. The required registration cursor or identification mark.
At present, there are mainly the following types of registration cursors in the paper feeding direction of the post-processing equipment such as the web bronzing machine and the die-cutting machine: rectangular marks, chromatic aberrations (which may be part of the printed pattern), and shared printing registration. Wedge mark. The registration cursor is typically produced on a printing plate of a key registration color for the corresponding processing operation. Pay attention to the following two problems when processing the registration cursor.
(1) The registration system of the individual brand model of the web printing equipment is not strong, and there is no interference within 30mm before and after the circumferential registration cursor, such as product pattern, gravure registration mark, color block, etc. Can achieve 20mm anti-interference ability, individual equipment even requires the registration cursor can not have other interference patterns in the entire circumference, but this will affect the future production costs, should be investigated when purchasing equipment.
(2) Most of them use rectangular marks with a width of 3 mm and a length of more than 5 mm, generally 3 mm × 7 mm. Individual brand gravure presses use Eltromat's Sincon-star registration system or Bobst's Registron registration system to directly identify printed register wedge markers, as well as individual designs using camera micro-pointing The sensor is detected and the cursor is extremely small. The solution is expensive and uses less.
If conditions permit, the number of circumferential registration cursors within each repeating perimeter is as close as possible to the post-processing hot stamping, die-cutting cycle, or proportional. For example, the hard case is generally 18-print, 18-hot, 24- or 30-die. In this case, consider setting a registration cursor in the empty position of each horizontal row for hot stamping and die-cutting. The common use of the register can not only improve the recognition ability of the registration cursor of the post-processing equipment, but also shorten the registration time of the post-processing equipment and reduce material waste.
2. Axial (horizontal) registration cursor design
The axial (horizontal) registration is mostly realized by the correcting and guiding device. The register cursor is generally a continuous tracking line with a width of 0.5 to 2.0 mm. The individual gravure printing machine also uses the tracking line to be laterally corrected, and the tracking line can be shared. . It should be noted that the tracking line is not required if the system is used to identify the printed register wedge mark and the register signal is used to directly drive the corrector.
The correction system with individual spot probes has low precision and anti-interference ability, and requires 2mm blank on both sides of the tracking line. There can be no interference, which will cause waste of paper. Correction and guidance system using CCD/CMOS probe.
For laser transfer paper, especially the light column laser paper, if the registration cursor is directly printed on the laser area, the registration photoelectric probe is prone to diffuse reflection when reading the mark, the signal waveform is unstable, the overprint fluctuation is large, and the printing package is generally pre-prepared. Leave a separate white or silver side.
The reserved white or silver edge is generally 10 to 12 mm. For the hard-packed small box, the horizontal dimension of the imposition is generally 730 to 735 mm. If the device uses a correcting and guiding system that supports the CCD/CMOS probe, the width of the tracking line in Figure 3 is 1mm, coincides with the bleeding position of the product, which can save 4~6mm paper .
3. Design of other marks
Roll stamping and die-cutting may require additional markings, such as cross marks reserved for hot stamping, die-cutting, and printing key color registration checks.
These marks are mainly used to facilitate the inspection of the key color of the printing process, the offset of the hot stamping, the unevenness, and the die-cutting, and the effect of the inspection machine to identify the offset of the overprint.
Optimization of Rolling Laser Printing and Overprinting Process
As mentioned above, for the optical column laser paper, a separate 10 to 12 mm white or silver edge should be reserved. For large batch products, long-term production has a large fixed loss. Individual models of gravure presses, such as Bobst's newer models, can upgrade their Registron registration system, add signal amplification and filtering systems, and upgrade the registration software algorithm to directly register the cursor Printed in the laser column of the light column, so that no white or silver edges are needed, and the registration can be guaranteed.
If the registration system of the gravure printing equipment is difficult to upgrade, but the number of printing color groups is sufficient, after repeated experiments, we implemented a reverse overprinting method for peer reference, and printed all the registration cursors in the finished material area. Before the first color is placed on the cursor, the ink opaque ink bottom is printed, such as white or silver, to cover or partially block the strong reflected light of the light column, thereby reducing the diffuse reflection, so that the signal clutter read by the register photoelectric probe is more Less, the waveform is stable, the first color of the bottom is based on the second color, and the reverse tracking overprinting can also achieve registration. At the same time, the reverse registration tracking monitoring can be added between the color groups, so that 10~ can be removed. 12mm white or silver edges save paper. Taking the strip case as an example, the width of the paper is reduced from 740 mm to 730 mm, and the imposition diagram is shown in FIG. The box product is inserted and spelled, and the register cursor is placed in the remaining material of the insertion, and the paper saving rate reaches 1.4%.
The above content is some of the experience that the author has summarized in the design and optimization of the round-press printing process of cigarette packets. I hope to help the industry peers to inspire the same process. In the next article, the author will discuss the design and optimization of the circular stamping and die-cutting process of the cigarette wrapping paper, especially the practical effects and optimization ideas of the various markings mentioned in the post-processing, please continue to pay attention to .