The whole solution of flexible packaging printing - prepress and gravure printing points

The tightness and fragrantness of soft packaging materials in food packaging cannot be achieved and matched by other packaging materials. It can maximize the original taste of foods.

Flexible packaging printing can take different printing methods, the most important form of which is flexographic printing, gravure printing. In Europe and America, more than 80% of flexible packaging uses flexographic printing because of its high environmental protection, long printing plate life, low pressure in the printing process, and high printing speed, and it has become the mainstream printing method for flexible packaging, but it has not been popularized in China.

In China's flexible packaging market, more than 90% of products use gravure printing. Gravure printing has the advantages of thick ink layer, bright colors, high printing resistance, wide range of printing materials (both plastic and paper), and good pattern continuity. However, it is deeply loved by manufacturers, but the gravure platemaking cost is high and the cycle is long. In the process of making plates, inks, and solvents, there are chemical materials that the human body has a certain degree of damage, and it is easy to cause environmental pollution.

Prepress preparation work should be improved
Prior to printing, quality control should be carried out, from the design, plate making, selection of packaging substrates to matching inks, printing equipment and printing technology, etc., careful and reasonable planning, every procedure must be strictly controlled, for the smooth product Get ready for listing. Planning and design is the first important point of product launch. Designers must understand the principles of gravure printing and related process technologies in order to avoid rework and product obsolescence during the printing process.

The following is a brief description of the problems that may occur during gravure printing.

The printing process eight is
1. Determine whether the printing method is printed or printed
Before you start printing, you must first determine whether the printing method is printed or printed. After the determination, the type of film is determined accordingly, and the corona treatment surface is distinguished to determine whether the type of the printing plate cylinder is reversed or genuine; different types of diluents are selected for the printing ink.

2. Determine the appropriate temperature and relative temperature
If the temperature of the printing shop is too high, the relative temperature is too large to easily cause problems such as back sticking, discoloration, color transfer, blocking, and poor firmness of the printed matter. In severe cases, the ink will be decomposed and printed without color.

If the environment of the printing shop is too dry, in the case of fast printing speed, static electricity will be generated and the ink will move on the film; if the printing speed is slow, the surface of the printed product will be lusterless and dry. Problems such as paste version.

In general, the printing shop should control the temperature at 18 ~ 25 °C relative to the control of 55% ~ 75%.

3. Plate cylinder positioning to ensure balance
The balance of the plate cylinder depends on the printing equipment and the plate cylinder itself, but also by the installation conditions. When installing, be sure to determine the position of the various plate cylinders and install them firmly. The position is determined according to the registration line on the plate cylinder and the length of the plate cylinder. For keyless plate cylinders, be sure to tighten the screws.

4. Adjust the pressure of the impression cylinder properly
Impression roller uneven, there will be missing print, uneven color and other issues. If the pressure of the impression cylinder is too large, the printed pattern will have problems such as ghosting, unclearness and dullness; if the pressure of the impression cylinder is too small, the screen will be transferred poorly, the text will be unclear, etc. problem. When this happens, you should change to a high-quality impression cylinder and adjust the pressure of the impression cylinder.

5. Adjust the squeegee angle
The angle between the squeegee and the plate cylinder is generally controlled at 45-65°, and the precise angle should be further adjusted according to the depth of the cell depth and the printing speed. During the adjustment, it should be noted that the distance between the squeegee and the impression cylinder should match the printing speed. At the same time, the squeegee blade should be given an appropriate pressure. The pressure can be adjusted according to the specific conditions of the plate depth, overprint color sequence, and other specific conditions.

6. Adjust ink viscosity
When adjusting the working viscosity of the ink, on the one hand, the printing speed should be taken into account. If the printing speed is fast, the quick-drying type diluent is selected; if the printing speed is slow, the diluent should be sent out. In ink fountains, to ensure the consistency of print quality.

7. Tension control requirements
In order to facilitate printing and improve the printing speed, we installed a set of magnetic powder tension control system on the gravure press and at the feeding place to automatically control the tension. Some high-end gravure printers also installed computer tracking and automatic control systems on various color groups. For printers without a computerized registration system, the tension in each color group must be adjusted manually. In the adjustment process, the matching of printing speed and tension should be considered comprehensively.

8. Drying system to adapt
The drying system affects the speed of the gravure printing machine. From the single oven to the double oven or multifunctional oven and drying tunnel, the main function of the drying system is the same; one is to increase the speed of the printing press; the other is to increase the speed. The fastness of the ink on the surface of the film allows the diluent in the ink to dry completely to prevent false drying and cause back odor or odor after bag making. Therefore, the drying system should work well with the speed of the printing press, grasp the amount of hot air of the equipment, and adjust it appropriately. Then adjust the temperature and air volume of the oven according to the size of the pattern area on the surface of the printed matter.
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