Analysis of the factors affecting the life of flexible printing plate

In the printing production process of flexographic printing presses, flexographic printing plate material is a key factor in determining the quality of printing. In addition, the price of flexographic printing plates is very expensive. Therefore, every effort is made to improve the printing durability of the printing plate and protect the quality of the printing plate , It is particularly important in the actual production process. In the actual production process for several years, I was fortunate to personally participate in the ARSOMA EM410, a seven-color plus a set of screen-printed eight-color flexographic printing machine manufactured by Jielas, using DuPont and BASF plates to print stickers, The production process of film internal standard, color box, disposable Paper Cup, oil standard and other products makes a simple summary of the factors that affect the service life of the flexographic version. The following five aspects can be summarized.

1 Influence of printing pressure

In the printing production process, fine dot printing plates with a high number of screen lines, such as 150 lines and 175 lines, are easily damaged and are the places that need protection most. Just after the new flexographic plate is attached to the plate cylinder, there is almost no fixed adjustment range for the pressure (because it is 410mm wide). Therefore, before adjusting the pressure, the parallelism of the three rollers (anilox roller, plate roller, and platen roller) should be adjusted well, and the precision of adjustment should be very high. Under the pressure-off state, the speed of the printing machine is adjusted to a low speed, and then the pressure is slowly and evenly balanced, so that a slight ink trace appears uniformly on the entire layout, and slowly solidifies until each part is not emptied, so that you can make The small dots on the whole printing plate are subject to the least compression and abrasion, which plays a good role in protecting the small dots and extends the service life of the printing plate to a large extent. Everyone knows that although the anilox roller, the plate roller and the impression roller are rolled, the anilox roller, the plate roller and the impression roller are compressed, and the linear speed of the three rollers is the same. Therefore, when the pressure is too large, due to the compression of the printing plate, there will be a certain sliding friction with the anilox roller, which will cause the printing plate to wear. When we adjust the parallelism of the three rollers, we can shift the plate cylinder slightly toward the impression cylinder, and the viscosity of the UV ink is slightly larger, which can alleviate the paste of high mesh lines and fine dots, and also can reduce the fine dots. Protected by abrasion, extending the life of the printing plate.

2 Influence of external factors

Flexible printing plates are very delicate, and must not collide with harder external substances or scratch, otherwise it will cause irreparable damage to the printing plate. When affixing the plate, the plate cannot be stretched vigorously. When compacting and removing the air bubbles between the plate and the tape, press the lower part of the palm perpendicular to the circumferential direction of the plate roller, but do not rub with your fingers. Avoid damage to small outlets.

3 Wiping method and influence of wiping materials

Wiping is a method that is adopted when the printing quality of white dots, ink filaments, dirty dots, etc. appears in the printing process. The materials used for wiping the plate are generally soft non-woven fabrics that do not lose fibers, or stockings with dense fibers and soft textures, or soft-bristled brushes (such as soft toothbrushes). The solvent used for wiping the plates is generally alcohol. The method of wiping the plate is generally to fold the four raw edges of the cut non-woven fabric in half with the center line, and then roll them into a roll along the edges. When you get your hand, use your five fingers to pinch the middle and lower part of the cloth roll. The length of the cloth roll is about half the length of the palm. It is better to put the other end of the cloth roll into the palm of your hand. In production, the plate-wiper is required to manicure and master the correct gestures. Generally, spray alcohol on the cloth roll first, so that the entire cloth roll is in a damp but not wet state. The effect of wiping the plate is the best, and the scrap rate is the lowest. Attention should be paid when wiping the plate, the strength of the field part can be slightly larger, and the strength of the fine screen with a high number of screens needs to be less. The cloth roll can be sprayed with more alcohol and wiped gently for a circle. You can also use a soft-bristled brush dipped in alcohol to find the part where the plate needs to be wiped. The movement direction of the brush should be the same as the movement direction of the plate roller. In the case of a cloth roll that cannot be wiped off, you can use a brush to brush the plate. Such a wiping method can better protect the printing plate from damage. [next]

4 The impact of the method

Plate washing is usually done with a soft-bristled brush, dipped in alcohol, and the brush should not be too strong. Wipe dry with a cloth while wiping until the plate is washed out of the original color. After brushing, dry with an air gun and store. It is better not to use absolute alcohol for alcohol. We use DuPont plates. The cleaning of such plates cannot use ester or ketone solvents. The direct contact between the printing plate and such solvents should be minimized. The UV ink also contains some ink that has a damaging effect on the printing plate, which will reduce the toughness of the printing plate or swell the printing plate. For example, the UV ink contains ester solvents, so the plate should be washed immediately after shutdown. In addition, when the printing plate uses UV ink, if the lubricant on the gear is stained, it will cause the printing plate to not be easily inked. If the time is too long, the printing plate will melt and scrap. Therefore, we must pay attention to the maintenance of the machine, adding an appropriate amount of lubricating oil to ensure the quality of the printing plate.

5 Impact of preservation methods

After printing, the printing plate should be cleaned, removed and stored. Please note when saving the printing plate:

● Prevent sun exposure. It is forbidden to store in places with high ozone concentration, and it can be wrapped and stored in black plastic bags or other materials to prevent sun exposure.
● The dryness, temperature and humidity (below 25 ℃) of the storage environment should be suitable.
● When storing, the printing plate and the printing plate should be separated by a foam sheet, the barrier should not be too high, about 20 sheets are more suitable, and heavier substances should not be placed on the printing plate. If the printing plate is improperly stored, the printing plate will become brittle and cracked. In severe cases, the printing plate will be scrapped.

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