Die cutting, cracking, plastic film processing

First, the issue of synchronization between die cutting and printing

Self-adhesive label printing is generally cut to a certain shape before it can be used. In the printing press die-cutting presses, the synchronization between die-cutting and printing is crucial. The up and down movement of the die-cut and the up and down movement of the printing table are driven by the main drive shaft, so there is synchronism, but the cutting position is determined by the distance of the traction roller controlled by the double crank structure, so the crank radius size and pressure are adjusted. Paper roll pressure is critical.

Second, the version of split

At present, China's self-adhesive label printing uses photosensitive resin letterpress, and this type of material often suffers from cracking problems. The following reasons are analyzed and corresponding solutions are proposed.

1. The roller diameter is too small

The smaller the diameter of the plate roller, the greater the tensile force on the plate, and the greater the force of the plate at the interface of the plate, so that the interface of the plate rises up, making it difficult to stick on the plate roller. . After printing on the machine, the pressure received here is greater than in other places, and it is easy to cause the plate to break. In this regard, a double-sided adhesive plate with a strong adhesive force can be used to seal the non-graphic portion of the plate interface with tape.

2. Excellent hardness

Excessive plate material can cause the plate surface to be too brittle, resulting in cracking. For this, a softer plate can be used. Our factory has once printed a full version of the live work. At the beginning, it used the Japanese Toyo textile KF-95GC model. It was cracked without printing for a long time, and later it was replaced by the softer EF-95GC model. Plate, troubleshooting.

In addition, in winter, the climate is dry and the temperature is low, so it is easy to harden the plate. Therefore, in the winter, the printing plate should be produced as much as possible; the temperature in the plate room should be kept at about 25°C and be equipped with a humidifying device; Sealed in a plastic bag; the printing shop maintains a certain temperature and humidity. If the plate becomes hard because it is left unused for a long period of time, the back of the plate can be washed with hot water to make it soft. However, if a resin plate is used, since it is soluble in water, it is necessary to prevent the water from coming into contact with the graphic part on the front side of the plate. Otherwise, it is very easy to damage the graphic.

3. Printing pressure is too large

Excessive printing pressure can also cause the printing plate to rupture. This phenomenon is especially likely to occur when there is a real map text at the plate interface. Therefore, in the printing process, under the premise of ensuring that the picture is not false, the printing pressure should be reduced as much as possible.

4. Unreasonable layout

Some layouts are on the ground from beginning to end, and the diameter of the printing roller is too small. When the printing plate is on the plate, the printing plate is easy to pick up. If you choose a roller that is a bit larger than the actual step size, leaving a small amount of plate base at the edge of the plate during plate making can make the plate more easily attached to the plate roller, greatly reducing the occurrence of plate cracking.

Third, plastic shadow

In relief printing, the graphic part of the plate is higher than the non-graphic part. When the ink on the plate roller is transferred to the plate, the non-graphic part of the plate is not inked, and the plate is relative to the non-image. The text part of the ink has no place to transfer. Due to the small number of ink rollers in the letterpress printing press, the residual ink on the printing roller cannot be evenly opened in time, resulting in partial imbalance in the amount of ink, and the local ink volume is greater than the amount of ink required for printing, so that the local graphic color of the printing product is deep It produces glue shadows in other parts.

It can be seen from this that there is a great relationship between the production of the backlit film and the design of the ink path of the self-adhesive printer. There are several ways to solve the glue shadow.

1. Increase the number of uniform ink rollers in the unit

Add a few more ink rollers in the printing unit so that the ink layer on the printing roller is more evenly transferred to the printing plate, which greatly reduces the depth of the re-emulsion.

2. Transform the printing roller

For some long-lived jobs, the diameter of the reel roller is transformed into the same thickness as the roller, which can also greatly reduce the depth of the re-emulsion. The principle is that the ink layer on the plate roller is consistent with the relative position of the ink area on the plate roller, and the ink layer thickness is relatively stable. This method is suitable for satellite self-adhesive label printers.

3. Adjust the way to ink

The specific method is to open the ink teeth, adjust the ink nails to control the size of the ink. This can ensure the ink required for printing at the same time, so that the ink is transferred to the ink roller as evenly as possible, in order to facilitate the ink to be more evenly transferred to the roller, to reduce the back of the plastic film.

Fifth, ink does not dry

There are many reasons why ink is not dry, mainly in the following aspects.

1. Too much ink supply

Ink supply is too large, resulting in too thick ink layer, UV light can not dry dry ink, this phenomenon occurs mainly in the printing of live work. When this happens, the amount of ink can be reduced as much as possible without affecting the print quality. If you can not achieve good results, you can consider moving the field to the first few groups of printing unit printing, so that after baking a number of UV lamps, the failure will be reduced.

2. UV lamp power is not enough

UV lamp aging or other causes UV lamp power is not enough, it will lead to ink quit. In this regard, the power of the UV lamp is adjusted to the maximum level, and if it does not, it is solved by changing the UV lamp.

3. Printing speed is too fast

Excessive printing speed can cause UV lamps to dry out. This can be solved by replacing the printing unit or reducing the printing speed. When printing live jobs, the printing speed should be kept at about 20 meters/minute.

Eight, printing hanging dirty

In the printing process, there are often some inconspicuous dirty phenomenon. The following is an analysis of this problem.

1 fixed hanging dirty

This is mainly due to dirt on the surface of the printing plate or the upward curl of the edge of the printing plate, which shows that there are dirty spots at the fixed position of the printed graphic. If it is caused by a plate curl, the graphic part has a line, the color of which is the same as the printed color of the tilted plate, and the cleaning of the layout or the portion where the edge of the plate is lifted can be solved as it is.

2. Not fixed dirty

This situation is mainly due to dirty or crusty wounds on the plate roller. The solution is to carefully inspect and replace the hard roller or clean the dirt on the plate roller.

3. Cockroaches cause a similar phenomenon

In the process of paper feeding, when the paper reaches the edge of the UV lamp, or if there is a foreign matter in the paper platen of the machine, the surface of the paper may be scratched. When the ink is printed on it, a similar effect may be caused. In particular, when a relatively thick film-type sticker is printed, the material is deformed by heat due to exposure to a UV lamp, and this phenomenon is more likely to occur. In this regard, careful observation should be made to find out where the paper is being picked up, and to remove the dirt by adjusting the angle of the UV lamp or cleaning the platen roller.

4. Large amount of ink causes dirty or dead

Letterpress printing is an anhydrous printing method. When the amount of ink is large, it is very easy to cause dirty or dead parts of graphic parts. In addition, the ink is too thin and it is easy to paste and cause the image part to be crushed. The solution is to minimize the amount of ink or increase the viscosity of the ink according to the requirements of the job.

Above, we analyzed several common problems in the label printing and hoped to help everyone in their daily work. Of course, in addition to these reasons I have mentioned, there are many factors that contribute to the poor quality of self-adhesive labels. I hope that everyone will carefully summarize them in future work, learn lessons, and continuously improve product quality.