Flexo Printing Overview

Flexo printing, offset printing, gravure printing and screen printing are the most common four printing methods in the world. They have their own characteristics and they have their own merits. In the developed countries such as Europe and the United States, flexographic printing has developed rapidly. Packaging printing has changed from gravure and offset printing in the past to flexographic printing, and about 70% of packaging materials use softness. Edition printing.
In our country, with the development of the commodity economy and the continuous improvement of people's living standards, the packaging and printing industry is also moving toward the development of high-grade, refined and multi-variety products. However, the market share of offset printing and gravure printing is quite large, and the start of flexographic printing in China is relatively late, especially in the printing of high-end products. With the continuous application of new technologies, flexographic printing has made great progress. The quality of products has followed the offset printing and gravure printing, and it has a very strong market competitiveness.
First, the characteristics of flexographic printing
Comparing with gravure, offset and traditional embossing, flexographic printing has its own distinctive features:
1, less equipment investment, quick effect, high efficiency. Comparing with the gravure printing machine of the same color group and the corresponding offset printing machine, the flexographic printing press is much lower in price. In addition, the flexographic printing press integrates various processes such as printing, die-cutting, and glossing, and multiple processes can be completed at one time, eliminating the need for additional post-processing equipment and providing high return on investment.
2, the device structure is relatively simple, so the operation is relatively simple and convenient.
3, high production efficiency. Flexographic printing uses roll materials, which can not only achieve double-sided printing of printing materials, but also can complete the work of on-line light (or lamination), bronzing, die cutting, waste discharge, and winding. It greatly shortens the production cycle, saves manpower, material resources, and financial resources, reduces production costs, and improves economic efficiency.
4, the range of printing materials is relatively wide, such as paper, plastic film, aluminum foil, sticker paper and so on.
5, the quality of the printed matter is good, the printing precision can reach 150 lines/inch, and the printed matter has rich layers, vivid colors, good visual effects, and is particularly suitable for packaging and printing requirements.
6, the use of new type of water-based ink and solvent-based ink, non-toxic, non-polluting, fully in line with the requirements of green environmental protection, but also to meet the requirements of food packaging.
Second, the flexographic printing process
It mainly includes two major steps of plate making and printing. The plate making process is generally:
Manuscript - film (positive chart) - back exposure - main exposure - developing rinse - drying - post-processing - after exposure - stickers for printing on the machine.
The printing process is generally as follows:
Printing materials - printing (including reverse printing) - Varnish or lamination, etc. - Die cutting - cutting - inspection - storage
Third, production precautions
1, manuscripts and customer requirements, select the appropriate number of color printing, color sequence, format and the corresponding version of the roller (number of teeth, mesh, etc.).
At present, many of the flexographic printing manuscripts are transferred by offset printing. There is a big difference between the two printing processes. Therefore, it is not possible to copy the offset printing process (especially the color separation and plate making process) according to the flexographic version. The characteristics of the printing process itself, combined with the performance of the company's flexo printing press to process the manuscript, and coordinate with the customer.
2, printing pressure, printing speed and the adjustment of the tension of each part should be appropriate.
Because the flexographic plate is composed of a harder polyester plate base and highly elastic photosensitive material, its most obvious feature is its elasticity. In the printing process, it is necessary to apply a certain amount of printing pressure. Although light pressure printing is used in flexographic printing, a slight change in the printing pressure may also cause changes in color and gradation reproduction, resulting in the enlargement of image dots on the printed matter. In addition, the printing pressure is so great that the outlets are enlarged.
The printing speed must be set according to the specific production conditions. When the machine starts up, it starts from a low speed, adjusts the position of the printing plate cylinders of each color group, and then gradually increases the machine speed after the registration, and it must adapt to the drying performance of the ink. It should be noted that the speed of the machine should not be too fast to prevent splashing, causing unnecessary waste and even affecting production.
The adjustment and control of the tension is very important. If the tension is improper, it may lead to failures such as overprinting of the printed matter, deviation of the material, and irregular winding.
3. During the printing process, the viscosity, pH, and drying performance of the ink must be checked at any time.
For the control of flexo printing inks, these are the three main aspects. In the production process, due to the volatilization of water and solvent, the performance of the ink becomes unstable, the viscosity increases, the pH value decreases, and the printability is affected. Therefore, in the printing process, appropriate amount of PH stabilizer or corresponding solvent (to be combined with specific printing speed and ink drying conditions) is added at regular intervals to adjust the pH and viscosity of the ink. At the same time, since the flexographic printing is a short station printing, the stroke between color and color is relatively short, and if the solvent in the ink is not completely dried, it will lead to poor stacking or blocking. (Packaging newspaper)