Analysis of the Factors Affecting the Life of Flexible Plates

In flexographic printing press production, flexographic printing media is a key factor in determining the quality of printed products, and the cost of flexo printing plates is very expensive. Therefore, every effort is made to improve the printing plate's printing rate and protect the quality of printing plates. It is particularly important in the actual production process. In the actual production process of several years, I had the privilege of personally participating in the production of ARSOMA EM410 manufactured by the Gallas Corporation. The eight-colour flexo printing machine with seven colors and a group of silk screens used DuPont and BASF's printing materials to print stickers and molds. The internal standard, color box, disposable cups, oil products and other products have a simple summary of the factors that affect the service life of the flexo, which can be summarized in the following five aspects:

First, the impact of printing pressure

In the printing production process, fine dot printing plates with a high number of screens, such as 150 lines and 175 lines, are easily damaged and are most in need of protection. After the new flexo plate has just been attached to the plate cylinder, the pressure has almost no fixed adjustment range (because of the wide width of 410). Therefore, before adjusting the pressure, the parallelism of the three rollers (anilox, plate roller, and embossing roller) should be adjusted well, and the adjustment accuracy should be high. In the state of pressure separation, the speed of the printing press is adjusted to a low level, and then the pressure of the printing press is slowly balanced, so that the ink on the whole layout is even and slightly faded, and it gradually becomes true until all parts are not filled with imaginary ink. It can minimize the squeezing and wear of the tiny dots on the whole printing plate, and it can play a better protective role for the fine dots, and extend the service life of the printing plate to a great extent. As we all know, although the anilox roll, the plate roll, and the embossing roll are rolling, the anilox roll, the plate roll, and the embossing roll are compressed, and the three rolls have the same linear velocity. Therefore, when the pressure is too large, a certain sliding friction occurs between the plate and the anilox roller due to the compression of the plate, so that the plate is worn. When we adjust the parallelism of the three rollers, we can slightly offset the plate cylinder to the impression cylinder. The viscosity of the UV ink is slightly larger, which can relieve the stencils of the fine dots of the high-line lines, and can also make fine dots. It is protected from wear and prolongs the life of the printing plate.

Second, try to avoid external factors causing damage to the printing plate

Flexible printing plates are very squeamish. Do not collide with harder external materials or scratch them. Otherwise, the plates will be irreparably damaged. In pasting, the plate cannot be strongly stretched. When compacting and driving off the bubbles between the printing plate and the tape, the lower part of the palm of the hand is pressed perpendicular to the circumferential direction of the plate roller but cannot be caught by the fingers. It is possible to do small damage to the network.

Third, the correct use of the rubbing method and the rubbing plate material

The rubbing version is a method that is adopted when the printing quality of white dots, ink, and dirty spots occurs in the printing process in the production process. Rubbing plates during production must require skilled workers. The material of the rubbed version is generally a soft, non-woven non-woven fabric, or a tight fiber, soft stockings, or a soft brush (such as a soft toothbrush). The rubbed version of the solvent is generally alcohol. The method of wiping the plate is generally to cut the four burrs of the cut nonwoven fabric into half the size of the original area in the inner line, and roll it into a roll along the edge. When you get your hand, use your fingers to hold the middle and lower part of the roll. The length of the roll is about half the length of your palm. The other end of the roll is placed in the palm of your hand. It is also possible to roll an ordinary cloth into a roll, put it back into the bottom of the stockings, and then put it back one or two times. A sock will roll the cloth in two or three layers, and the length is still half the length of the palm. In production, the cleaners are required to perform manicures, and they must also have the correct gestures. In general, alcohol is sprayed on the roll, so that the entire cloth roll is in damp and wet condition, the best effect is to wipe the plate, and the reject rate is the lowest. Pay attention to the intensity when erasing the printing plate, the strength of the field part can be slightly larger, the screen plate, especially the small screen plate of the high network line number, the intensity requirement is minimum. The cloth roll can be sprayed with more alcohol, wipe gently, and the wipe time is a circle. You can also use a soft-bristled brush to fill the alcohol and sight the position of the mass. The brush head moves in the same direction as the plate roller. You can use the brush to brush the plate without rubbing it off with a roll of cloth. This rubbing method can better protect the plate from damage.

Fourth, wash the method

Washing the plate means that when the printing machine shuts down, we will wash the plate clean, remove it and store it. Washing the plates is usually done with a soft-bristled brush, which is filled with alcohol. The intensity of the brushes should not be too large. Wipe them with a roll of cloth until the plates are cleaned. After the brush is clean, dry it with an air gun and store it. It is best not to use anhydrous alcohol. We use DuPont's plate. We must not use lipids and ketone solvents for cleaning such plates. We should minimize the direct contact between printing plates and such solvents. In the UV ink also contains some of the ink damage to the printing plate will make the plate toughness reduce or make the plate soaked, such as UV inks contain lipid solvents, so wash immediately after shutdown. In addition, when the printing plate is used with UV ink, if the oil on the gear is stained, it will cause the printing plate to be not easily inked, and if it is too long, it will cause the printing plate to swell. Therefore, we must pay attention to the maintenance of the machine, add oil to the right amount, in order to protect the quality of the printing plate.

Fifth, the correct preservation of the flexographic printing plate

After printing, the printing plate should be cleaned and removed for preservation. When saving the printing plate, pay attention to:

1, to prevent the sun. It is forbidden to store in places with high ozone concentration. It can be wrapped in black plastic bags or other materials that prevent sun exposure.

2. The dryness, temperature, and humidity (below 25°C) of the environment where the place is stored should be suitable.

3, when stored, the printing plate and the printing plate are piled up, the middle must use the foam slice to divide, the base cannot be too high, 20 or so are more appropriate, moreover the printing plate above cannot put the heavier material. If the plates are not properly stored, the plate will become brittle and cracked. In severe cases, the plates will be scrapped.

The above points are some of the factors that affect the life of the printing plate that are summarized in the production process and are discussed with peers.



Author/(South Jingsheng)

Source: Shanghai Packaging