Offset printing, there are many factors, will affect the ink scraping is not clean. This paper lists ten factors affecting ink scraping for your reference
Ink viscosity too high
When the ink viscosity increases, its surface tension also increases, and the mutual force also increases, so that the scraper will increase the impact force of the ink on the scraper in the process of touching the ink, and damage its balance point. The scraper can not clean the roller completely, which directly affects the product quality.
The pressure of the scraper is too small. Under normal conditions, when the machine is just started, the pressure of the scraper is usually set very small. With the advance of the machine speed, the impact force of the ink on the scraper on the plate roller will increase with the advance of the machine speed, damaging the original balance point and directly forming the scraping unclean.
Ink water or use time is too long, ink in the use of a long time, on the one hand, in the long-term cycle process, the pigment in the ink will continue to separate out, make the ink composition changes, on the other hand, the water vapor in the air will condense due to the evaporation of solvent, into the oil and ink, the same makes the composition of the ink change. Then change the entire function of the ink, so that the ink scraping function is greatly reduced, directly increasing the scraping difficulty of the scraper, forming the attack of scraping unclean.
If the solvent dries too fast or slowly, and the mixed solvent dries too fast, in addition to making the ink viscosity advance in a short time, it will also cause the ink to adhere to the plate roller. Because the solvent transpiration is too fast, the ink adhered to the plate roller will be gelatinous. When the plate roller passes through the scraper, due to the high adhesion of the gelatinous ink, the scraper can not scrape it off after a week's operation, Then it is directly brought to the printing substrate to form a scraping attack. The solvent itself transpiration is very slow, and some of the ink on the roller can not be dried and fixed on the surface of the roller in time. The situation is similar to that of some inks with dot points. When the printing substrate passes through the roller, some ink on the roller can be easily transferred to the printing substrate, forming an attack of scraping.
The use time of the roller is too long. Due to the long-term use, the surface of the roller will be worn due to the force of the scraper, and the surface will be more and more lubricated, which will make the affinity between the ink and the roller more and more strong, which directly increases the difficulty of scraping the scraper and constitutes the attack of scraping unclean.
The scraper device is too soft, the angle and the flat blade device are too soft, and the angle is normal. Due to the effect of air pressure, the scraper will bend on the surface of the plate roller, that is, the scraping point. The way of scraping is not the "point" connection, but the "surface" connection. Thus, it can not effectively scrape off some of the idle ink on the plate roller, that is, there is no dot or some ink scraping off, which constitutes the attack of scraping unclean.
The plate roller device is not concentric, the plate roller device is not concentric phenomenon, under normal circumstances, the jump within 10 wires will not affect the overprint and product quality. When the plate roller is working from the side with longer oval diameter to the side with shorter oval diameter, the distance between the two sides becomes longer. Because the scraper is acting on the plate roller by external force, there is a time difference in the process of changing, that is to say, the pressure of the scraper is relatively reduced within a period of time, so the pressure of the scraper is tight within a plate circle due to the jump of the plate roller Loose, and then constitute some scraping unclean phenomenon.

Solvent question 1, because the solvent is to participate in the use of ink, so the solvent water will directly damage the entire function of the ink, constitute scraping unclean.

2. Solvent ratio is not appropriate, will directly constitute ink fast dry or slow dry, constitute scraping unclean.
3. The solvent itself has impurities, such as low purity, high water content.
On the one hand, the ink without circulation will make the viscosity difficult to control; on the other hand, due to the thixotropy of the ink, the various functions of the ink will be reduced when the ink is not recycled. In addition, because of the non circulation, the ink surface crusting in the ink tank will be formed, which will directly increase the time for the dry ink to adhere to the plate roller, forming the phenomenon of scraping unclean.
Since the surface of the inkstick is convex, some ink will adhere to it more or less after use. With the increase of application times, the amount of ink will also increase. When the solvent transpiration is complete, the dry ink will remain. In the following application process, due to the ink in the ink tank can not completely protrude the surface of the inking stick, some dry ink is wetted, and the ink forming strong gel is transferred to the surface of the plate roller in the process of ink mixing along with the plate roller operation. Due to the strong adhesion, the scraper can not scrape it off under the condition of the plate roller operation for a week, and then it is directly brought to the printing substrate, forming a scraping unclean Net attack, this phenomenon is especially no dot some more obvious.
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