What Is Involved in the Gravure Printing Process?

Gravure printing is to fill the entire printing plate surface with ink, and then use a special ink scraping mechanism to remove the ink in the blank part, so that the ink only stays in the mesh of the graphic part, and then under the action of large pressure , Transfer the ink to the surface of the substrate to obtain printed matter. Gravure printing is direct printing. The graphic portion of the printing plate is recessed, and the degree of the depression varies with the level of the image. The blank portion of the printing plate is convex and is on the same plane. ^[1]

Gravure printing is referred to as gravure printing, which is one of the four printing methods. Gravure is a direct printing method that will

One of the basic printing methods. The graphic of the printing plate is lower than the blank part. When printing, the whole plate is inked, and then the surface of the plate is scraped, so that only the ink in the graphic portion is left and transferred to the substrate to become a printed matter. Can be divided into engraving gravure, photo-etched gravure and electronic engraving

The types of gravure printing are divided into two categories according to the plate making method:

Gravure printing due to

The ink carrier in gravure printing is a pit carved on the printing plate. The shape of the pit is the same as that of the original picture.

According to the actual situation in China, there are three methods for digital plate making of gravure: electronic engraving machine method, laser engraving and post-etching treatment method, and laser ablation plate making method for electroplated alloy.

Electronic engraving machine

Electronic engraving machine is a precision machine with high quality and stability, using modern technologies such as integrated automation control. All production data of electric carving are collected in digital form, which can be used in subsequent jobs with high reliability. The originals become digital signals from the beginning of scanning and are sent to the software for color separation and then transmitted to the electric engraving machine or color proofing machine. This is very beneficial to the standardization and standardization of the production process, and thus more guarantees the quality of the printed matter. And the engraving workstation uses TIFF graphics and text data for transmission, through HelioLight group workstation for convenient integration and setting of working parameter configuration, the engraving software generates the engraving curve, records the engraving parameters and displays the engraving status, until the burned disc saves the file (Easy to use and modify many times).

The electro-engraving process is relatively mature, the control is simple, and the level reduction is realistic. The disadvantage is that the amount of ink on the field is limited, and the ink layer has insufficient covering power for some rough substrates. Due to the division of the mesh wall between the mechanically carved meshes and the meshes, the edges of the lines composed of the meshes are inevitable. , When printing, the small text is not clear and easy to break or paste. However, Haier, Germany recently launched the new Xtreme engraving technology, which can reproduce the most subtle parts very finely at a network line number of up to 400 lines / cm. Fine text can independently select the recording resolution independently of the number of engraving network lines. The ink flow smooths the contours and produces contour lines. Not only can achieve the conventional outlets, but also can achieve FM screening and replication.

Laser engraving and post-etching process

Laser engraving and post-etching technology is another advanced digital plate making method after electric engraving. It accepts color separation processed image files through the interface like electric engraving, and sends the screened graphic signals to the laser modulator. The laser acts on the pre-coated protective layer on the surface of the roller to expose the copper or iron bottom, and then after different times of corrosion, pits of different sizes are formed on the roller.

The laser engraving process overcomes the weakness of the electric engraving text and the thin lines of hair, making it weak, highlighting the characteristics of high ink content, thick color, clear handwriting, and durability. Compared with the traditional photogravure platemaking, it has high screen accuracy. , Arbitrary editing mesh, no seams and other advantages. It is suitable for printing plates with particularly small text but high definition, such as cigarette printing and anti-counterfeiting printing. It is widely used for high-precision anti-counterfeiting printing such as currency, securities, and ticketing, and high-grade tobacco and alcohol packaging. More advantages in the process.

In addition, there is also a photosensitizer laser method, which uses violet laser light to expose the photosensitive layer of the graphic part and then rinses it. Other processes are basically the same as the laser engraving method.

Laser ablation for plated alloys

The extensive application of laser ablation technology in gravure will rapidly spread with the development of laser technology. It does not require mechanical adjustment, thin lines and characters are clearer, and it is easier to control levels than corrosion. The latest laser engraving machine currently on the market, it uses high-resolution laser to perform fine engraving directly on the surface of the copper drum. The contour, halftone dot distribution and depth of the sculpted information can be arbitrarily changed, so as to achieve the output effect previously only achieved by laser imagesetters.

Advantages: The ink expressiveness is about 90%, and the color tone is rich. Strong color reproduction. Strong layout tolerance. The number of prints is huge. A wide range of paper is used, and materials other than paper can also be printed.

Disadvantages: plate making costs are expensive, printing costs are also expensive, plate making work is more complicated, and a small number of prints are not suitable.

Application range of gravure printing

Engraving gravure printing, because of its exquisite lines and not easy to counterfeit, are all used to print securities, such as banknotes, stocks, gift certificates, stamps, and vouchers for commercial reputation or

In addition to books and magazines, newspapers, gravure printing is mainly used for packaging and decoration materials. According to the characteristics of gravure printing, printed materials should meet the following quality requirements.

Monochrome gravure prints with bright, medium, and dark tones with clear, coordinated, and delicate tone. The outlets are clear and complete. The layout is even and clean.

Color gravure prints: bright, medium, and dark tones are sharp, coordinated, and delicate. The colors are natural and harmonious. The dots are clear, complete and accurate in angle. The outline of the image is clear, and the overprint allows errors.

Appearance of printed matter: The layout is clean and uniform without obvious dirt marks. Images and text are positioned accurately. The color tone of the printing plate is basically the same, the size error of the fine print is not more than 0.5mm, the general print is not more than 1.0mm, and the overprint error is not more than 1.0mm. ^[3]

Failures in gravure printing are mainly caused by printing plates, inks, substrates, doctor blades, etc.

(A) uneven ink density

The phenomenon of periodic ink color changes on printed matter. The troubleshooting methods are: correct the roundness of the plate cylinder, adjust the angle and pressure of the doctor blade or replace it with a new doctor blade.

(Two) the mark is fuzzy and fluffy

The printed images are layered and fuzzy, and the edges of the text appear burr. Elimination methods include: removing static electricity from the surface of substrates, adding polar solvents to the ink, and appropriately increasing

1.Manual

1. Large and medium-sized packaging gravure printing enterprises will occupy the mainstream, especially cigarette packaging gravure printing enterprises will pursue scale efficiency, high quality and high technical content.

2. Due to environmental protection and sanitation, food, pharmaceutical, tobacco, alcohol and other industries are paying more and more attention to the environmental protection of packaging materials and printing processes. Gravure companies pay more attention to the environment of the printing workshop. Environmentally friendly inks and varnishes will be more and more popular, closed squeegee systems and quick-change devices will be promoted and applied, and gravure printing machines adapted to water-based inks will be widely used.

3. The independent drive technology of the gravure printing machine and the electronic shaft drive as the technology platform will realize the comprehensive upgrade of the gravure printing machine. The gravure printing machine for various purposes will use the electronic shaft drive. Electronic shaft drive and register systems are mainly from Japan and Europe, but they can only be applied to a small number of domestic gravure printing machines. The development of a domestic overprint system will be the key to the comprehensive upgrade of domestic gravure printing machines.

4. The proportion of wide-format gravure printing machines and paper gravure printing machines will continue to increase. On the one hand, the decorative printing (mainly grain paper printing) and carton gravure markets will grow rapidly. On the other hand, the scope of flexible packaging gravure printing machines will continue to increase, and the number of large-format gravure printing machines will increase rapidly. Paper and paper-based composite gravure printing machines (wood grain cigarette labels, aseptic packaging, gift wrapping paper, etc.) will grow rapidly.

5. The processing of gravure production line will be more diversified and the function configuration will become stronger and stronger, such as the above light, die cutting, cross cutting, soft label cutting, etc. Correspondingly, gravure printing press management systems and long-distance technical support systems will be adopted more and more. At the same time, in order to meet the needs of individualization, from unwinding, printing to in-line processing, rewinding and other parts will be modularized, the most important of which will be gravure carts or gravure interchange with flexographic printing Trolley.