Overprinting and gluing in flexo printing

Due to the advantages of in-line processing, combination of various printing methods, and use of environmentally friendly water-based inks, flexo presses have occupied a certain market in the high-end packaging and printing industry in China, especially in the printing of beer labels and soft packs. China has a great advantage. However, compared with offset printing and gravure printing, flexo printing also has some disadvantages, such as the large amount of deformation of the printing plate. These are specifically shown as misprints and stencil printing defects during the printing operation.
Imprinting is not allowed 1. Tension control

In the printing process, because the tension is not stable, a large amount of waste products are likely to occur, so the tension of the tape must be strictly controlled. In general, there is a magnetic powder tension controller and a tension driving roller at the unwinding and winding positions of the machine, and each has a tension display. Because the paper has joints, the tension will always fluctuate every time you pick up h. You can play ahead of schedule and reduce the amount of waste. If you want to replace the printing job, if the newly replaced tape is wider, the tension roller will often be worn due to the narrower tape on the front, and the wide paper will cause bridging effect in the middle of the roller. The two sides of the belt are tight and the middle is loose, which has a great influence on the rear slitting unit. At this time, it is necessary to replace the rubber roller, or to smooth the surface of the old rubber roller and continue to use it. In addition, the gas lifted spindle will become loose after a long time.

2. Ensure the accuracy of the printing plate, accurate alignment of the plate

At the time of loading, manual paste is generally used, which requires a high degree of proficiency. The edge of the plate must be parallel to the axis of the plate cylinder, and the seam should be as close as possible. Otherwise, it is easy to cause the plate at the seam. Roll beat. If a single printing plate is replaced separately, the overprinting of the printing plate is often inaccurate because of different plate-making time. At this time, the plate can be blown with a Hair Dryer, and then stretched longitudinally or laterally to keep the same with other printing plates.

3. Fixed speed printing

For large-volume prints, it is advisable to use constant-speed printing under conditions where the process is relatively mature, so that the effect of the drying device on paper deformation is relatively uniform and overprinting is easy. Other process parameters such as ink viscosity and tension settings can have a fixed range so that the quality can be guaranteed.

Paste version

In the design of high-end packaging products, in order to pursue the process of anti-counterfeiting, often design a number of fine lines and small text, as well as a large area of ​​solid color highlight the deep connotation, such as the Red River 88 soft package, white sand treasures and other soft packages. In order to make the ink solid in the field, two solid versions of the overprint are required, so that the stencils are easy to appear in the hollow fine text. The methods for solving such stencil problems are:

1. Too much paper on the paper

First check whether the electrostatic precipitator is working properly. If it is too dirty, clean it in time. The paper dust on the side of the paper roll can be wiped off with a slightly damp rag. The rag can also be filled with a nylon stocking and placed at a suitable place on the unwinding area to wipe off the paper on the paper roll.

2. Excessive printing pressure

Because the resin plate used by the flexo printer is easily deformed, if the pressure is too high at the time of starting, the area of ​​the graphic and text will be enlarged. The stenciled text strokes will be finer, and the paste will be easy to paste. When the machine is turned on, it is necessary to start from the first color group. Compression, while the slow observation of the pressure of the text, until the adjustment is appropriate and then boot, in addition to the use of a long time the printing plate will be aging and expansion, thin thin lines will also become thinner, then you need to replace the printing plate.

3. Overprinting is not allowed to cause paste

Two full-page versions of the field or screen are overprinted. If they have slight misalignment, then the thin lines on the prints will have a feeling of stencil. Generally, the hollow part of the ground edition is appropriately enlarged to reduce overprinting difficulty.

In short, understanding the characteristics of the flexographic printing process and the correct operation methods can maximize product quality and production efficiency, and avoid excessive waste products.