In the printing production process of flexographic printing presses, flexographic printing plates are the key factors in determining the quality of printed products. In addition, the prices of flexographic printing plates are very expensive. Therefore, every effort is made to increase the printing durability of plates and protect the quality of printing plates. It is particularly important in the actual production process. In the actual production process of a few years, I had the privilege of personally participating in the ARSOMA EM410 manufactured by the Gallas Corporation, a color printing machine with seven colors and a set of eight-color screen printing machines, and printed stickers using DuPont and BASF. The production process of the internal standard film, color box, disposable cup, oil label and other products has made a simple summary of the factors that affect the service life of the flexographic plate. 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 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 (since it is 410mm wide). 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 is slowly increased, so that the whole page of the layout shows a little bit of ink evenly, and it gradually becomes true until all parts are not empty. This can make The tiny dots on the whole printing plate are subjected to the least squeezing and abrasion, which plays a better role in protecting the fine dots and extends the service life of the printing plate to a great extent. As we all know, although the anilox roll, plate roll, and embossing roll are rolled, the anilox roll, plate roll, and embossing roll are compressed, and the three-roll line speed is the same. Therefore, when the pressure is too high, 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 high-line lines, and can also reduce the number of small dots. Protected by wear, prolongs the life of the plate.
2. Influence of external factors
Flexible printing plates are very squeamish. Do not collide with harder external materials or scratch them. Otherwise, the plates will be irreparably damaged. At the time of pasting, the plate cannot be strongly stretched. When compacting and driving off the bubble between the plate and the tape, the lower part of the palm of the hand is pressed perpendicular to the circumference of the plate roller but cannot be caught by the finger. Avoid damage to small outlets.
3. The effect of the rubbing method and the rubbing plate material
The rubbing version is a method that is used when printing quality such as white spots, ink, and dirty spots occurs in the printing process. The material of the rubbing plate is generally a soft, non-woven fabric, or a tight fiber, a soft stocking, or a soft hair brush (such as a soft toothbrush). The rubbing solvent is generally alcohol. The method of wiping the plate is generally to fold the four edges of the cut nonwoven fabric in half with the center line, and then roll it along the edge to form a roll. 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. In production, the cleaners are required to perform manicures, and they must also have the correct gestures. Generally, alcohol is sprayed on the cloth roll first to make the entire cloth roll in damp and wet state with the best effect, and the waste product rate is the lowest. Pay attention to the intensity when erasing the edition, the intensity of the solid part can be slightly larger, the small screen edition of the high net line number requires less. Rolls of cloth can be sprayed with more alcohol, wipe gently, and the wipe time is a circle. You can also use a soft-bristled brush, fill the alcohol, and identify the position of the part that needs to be wiped. The direction of the brush movement is the same as the direction of movement of 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.
4. Effect of washing method
Wash plates are generally used soft brush, fill the alcohol, the brush strength is not too much, wipe the edges while using a cloth to dry, until the plate cleaning out of the original color so far. After the brush is clean, dry it with an air gun and store it. Alcohol is best not to use anhydrous alcohol. We use DuPont's plate material. This kind of plate material should not be washed with esters or ketone solvents. We should minimize direct contact between the plate 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 swell, such as UV inks contain ester solvents, so immediately after the shutdown wash plate. 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, plus the amount of lubrication to ensure the quality of the printing plate.
5. Effect of saving method
After printing, the printing plate should be cleaned and removed for preservation. When saving the printing plate, pay attention to:
Prevent sun exposure. 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.
The dryness, temperature, and humidity (25Â°C or less) of the storage environment should be appropriate.
When depositing, the plate and the printing plate should be separated by a foam sheet. The base should not be too high, about 20 sheets are appropriate, and the printing plate should not be placed with heavier material. Improper preservation of the plate can cause the plate to become brittle and cracked. In severe cases, the plate is rejected.
Source: Xinhua Printing Network
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