Fine flexo printing common faults and elimination

There are pinholes printed in the field. 1. The printed surface is white and lustrous. Observe with a magnifier 25 times or more. You will find that there is an irregular, white, unprinted phenomenon in the field.
2. The cause of the incorrect use of double-sided adhesive.
3. Solution 1 Increase pressure, but sometimes it cannot be completely resolved.
2 Tune the ink to increase the fluidity of the ink.
3 Adopt the method of printing twice, but it is necessary to pay attention to the accuracy of the overlay.
4 The same number of anilox rollers with the same process parameters and a large amount of ink storage are beneficial for reducing pinholes.
5 double doctor anilox roller system, printing speed should not be too fast.
Fine Dots Dirty 1. Phenomenon Fine dots, such as 5% fine dots, will have some dots on the pattern. Either there is an ink spill around the circular dot, or two or more circular dot spots are stuck.
2. The main reason for the analysis is that the pressure is too great. There are two cases of excessive pressure:
1 In a machine with poor accuracy, the pressure is increased when the sudden change in pressure does not occur. That is, after one adjustment of imprinting, the pressure during operation changes greatly. This can be confirmed by the fact that in the case of the same process, material, product, and the same mechanics operation, the probability of the occurrence of dot-stucking on the product of one flexo press is greater than that of another flexographic press of a different type.
The sudden change in the plate caused a sudden change in pressure, which increased the printing pressure. For example, in the actual production, such an example is encountered. A ring pattern is designed with a gradient ring, the printing plate is 133 lines/in, the color depth is 85%, and the light color is 35%. The original process was arranged from dark prints to light prints. As a result, there were dot adhesions and non-stop printing. It was still impossible to solve the problem. Later, the printing plate was reversed, and the original printed one end turned into a post-print, and the layout was not easily dirty. . The reason is that from deep printing to light printing, the pressure is increased from 85%, and there is a jump from 0 to 85%. The ink on the dot is likely to spread around to cause adhesion. When changing from shallow prints to deep prints, 35% of them were put under pressure before they reached 85%, and the pressure changed from abrupt to gradual. The layout was not prone to stickiness.
3. Solution 1 Reasonably choose the ratio of printing plate line and anilox roller number. Theoretically, the ratio of the number of printing plate lines to the number of anilox roller lines is 1: (3 to 4). Under such a ratio, the ink is thick and colorful. However, it was found in production that if the accuracy of the press is slightly problematic, the above ratio printing is used, and the dot adhesion is highly likely to occur on the high-light screen screen. In order to print fine products with 120-130 lines/in or even 150 lines/in, 700-800 lines/in anilox rollers should be configured, and high-quality inks should be used to solve the problem of ink color.
2 Reasonably choose the double-sided adhesive for stickers. The low-density double-sided adhesive should be used, and its relatively soft characteristics, even if there is some abnormal impact, can be transferred without causing dot distortion.
3 Reasonably choose the printing speed. Raising the speed can often improve the easy-to-dirt problem in highlights. In essence, this is still a stress issue. The adjustment between the flexo printing machine anilox roller and the printing plate cylinder is mainly regulated by screw (some hand wheel) and high-grade machine stepping motor. Under high-speed operation conditions, even if the original locked-out mechanism has a certain degree of retreat with the increase of the vehicle speed, some high-grade flexo presses in foreign countries have stipulated that when the speed increases by 50m/min, the roller will be on the screw. The position is adjusted to 2 to 10 μm. If the speed of the drum does not increase, the position on the lead screw of the drum is adjusted. It means reducing stress.
Edge Profile 1. Phenomenon The edge profile is a feature of letterpress printing. Severe edge contour failures can cause fine-brush strokes, dead spots, hanged whiskers, pen strokes, etc., affecting the quality of printing; it can also cause poor drying, and the paper guide rollers can stain the printed inks with dirty ink. The reverse side of the winder is dirty and sticky, causing hindrance to the process, and it also increases the wear of the printing plate.
2. Reasons Analysis Plates are not smooth, there is wear, over stamping.
3. Solution 1 Adjust the pressure between the metal anilox roller, plate, and impression roller to minimize the contact pressure.
2 Adjust the layout height (pad), including layout grinding and tape on the back. For example, when field and fine strokes are drawn together, the field part should be slightly higher.
3 Adjust the ink according to the graphic conditions. For example, when the field is large, harder ink should be used and the printing pressure should be increased. (Man/Jinyinhe) ("Packaging and related industry information")