Unclear picture and text is one of the more common problems in gravure printing. The following discussion will be conducted from five aspects: human, machine, material, method and ring.
1. Human Factors
The lack of good professional ethics and responsibility of employees is one of the reasons for many major quality accidents. In order to ensure the quality of gravure printing, the professional ethics education of employees should be strengthened, and post awareness should be strengthened; employees are required to master the use and operation procedures of equipment.
2. Machine factor
In gravure printing, the problem of equipment that causes unclear graphics is that some related devices are not fully equipped or even equipped, and are not well utilized. These devices mainly include the following.
(1) Ink circulation device. The printing equipment of many enterprises is not equipped with an ink circulation device, and the ink is directly added to the ink tray, which results in insufficient circulation of the ink and poor fluidity, resulting in unclear paste and printed graphics. The ink circulation device includes two types of motor-type ink circulation device and pneumatic pump-type ink circulation device. The price of the motor type is lower, but the ink in the ink outlet slot will be blocked by the foreign matter in the ink, so that the ink will not be placed on the plate, causing deinking. It has a large amount of ink for the first time, which is easy to cause waste of ink. The air-pump type has less initial ink distribution, which can reduce ink waste, and there are few foreign objects in the ink blocking the filter screen and fire caused by overheating of the motor, which has high safety.
(2) The ink scraper swings from side to side. In order to extend the service life of the scraper, some companies often remove the left and right swing device of the scraper. This will not only cause failures such as unclear graphics and text, but also shorten the service life of the plate cylinder.
(3) Circulating water cooling device. The main function of the circulating water cooling device is to make the printed matter cool down quickly after leaving the oven, so as not to produce anti-sticking phenomenon and the mutual adhesion of the front and back sides of the printed product after winding. Because of its high cost, many printing companies often do not have equipment when introducing equipment. The direct consequences of doing so are twofold.
First, as the equipment runs for a long time, the temperature of the first guide roller passing by the printed matter after leaving the oven will quickly rise. When the temperature rises to a certain level, the resin in the ink will be hot, causing reverse adhesion , The printed graphics are not clear.
The second is that the ink or varnish on the printed matter enters the winding device before it is completely dry. When it is unfolded, the front and back sides will stick to each other, which also causes unclear printed graphics. In order to alleviate the unclear printed pictures and texts, it is recommended that you install the above devices in time.
3. Material factors
The main materials that affect the printing quality are: printing materials, inks, solvents and rubber rollers.
(1) Printing materials. The printing materials include plastic, paper, aluminized paper and aluminum foil. Our company mainly undertakes printing aluminum foil and aluminized paper. The surface treatment of aluminum foil is not good, too much oil stains will make the transfer performance of the ink worse, resulting in unclear printed graphics; and the effect of aluminum plating on aluminum paper is not good, the surface is uneven, the printed products will produce many bright spots, and the graphics will naturally Not clear.
(2) Ink. Any of the ink's viscosity, fineness, yield value, thixotropy, fluidity, adhesion, and other quality indicators that do not meet the printing requirements will affect the transfer of ink on the printing material, resulting in unclear graphics. In addition, too much impurity content in the ink will also affect the clarity of the printed graphics. When the old ink is used on the machine, it should be filtered, and a certain amount of new ink should be added, and the new ink should be replaced if necessary.
(3) Solvent. The purity of the solvent is low, and it contains too much fat or water, which is inevitably not conducive to the full dissolution of the ink, resulting in the impure color of the printed product, and the printed graphics and text are not clear and full.
(4) Plate cylinder. For gravure printing, the number of screen cylinder lines, the shape and depth of the mesh, the quality of the chrome layer, and the quality of the surface polishing treatment will directly affect the ink transfer rate in the mesh. If the ink transfer rate is low, the printed graphics will not be clear.
4. Method factors
The proficiency of the operation skills, whether the operation method is correct or not, and whether the operation is carried out in strict accordance with the operation rules have an important influence on the quality of the printed matter. In summer, the temperature is higher and the solvent volatilization speed is faster. At this time, it is necessary to reduce the blade angle, shorten the distance between the ink scraping point and the imprinting point, and reduce the volatilization of the ink solvent on the plate surface to reduce the occurrence of blocking. In the case of a slow solvent volatilization rate in winter, the opposite adjustment method is adopted to promote the volatilization of the solvent and reduce the occurrence of paste phenomenon. As another example, aluminum foil and aluminum-coated paper have different adsorption of ink, and different doctor blade adjustment methods should also be used. In addition, the blade pressure. The adjustment of the pressure of the embossed rubber roller, the tension of the printing material, and the volatility of the solvent should also use different adjustment methods according to the season and the raw materials.
5. envirnmental factor
The environmental sanitation is poor, flying dust and other debris will fall into the ink, causing quality problems such as knife wire, blocking version, etc., resulting in unclear printed graphics. If the ambient temperature is too high and the solvent volatilizes too quickly, the blocking phenomenon will also occur, resulting in unclear printed graphics. If the ambient humidity is too high, excessive moisture will penetrate into the ink, which not only reduces the purity of the ink, but also causes the phenomenon of fogging on the surface of the ink, causing the printed graphics to be dull and unclear. Therefore, the environment of the printing workshop should be clear and clean, and the temperature and humidity of the environment should be kept as constant as possible.
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