Causes and solutions for the knife mark line
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Causes of scraper line marks
1 no ink line marks. Mainly the ink is mixed with hard inorganic impurities, such as sand, which are embedded in the edge of the blade to cause line marks. Sometimes such scraper line marks are also dashed, and the appearance of such scraper line marks can easily damage the print and the doctor blade.
2 thicker continuous line marks with ink. This is mainly due to the fact that some of the thicker soft particles or impurities are caused by the squeegee or the blade edge is damaged. This is the simplest and most common scraper line mark.
3 "Meteor" shaped scraper line marks. Such scraper line marks are generally present in the screen dots of the printing plate which are very shallow or unengraved, and are present at a time when the product quality is extremely harmful. The causes of such scraper line marks are more complicated. Over the years, people have been explained from ink, plate making, printing environment, etc., but so far, no one is perfect. Better is the "active particle hypothesis."
4 filament-like continuous scraper line marks. Such scraper lines are small, like hair strands, often appear in the printing process, and are difficult to observe on the printing machine. When a large number of products have been printed at the time of discovery, the quality is extremely harmful. Such scraper line marks can be divided into two types, one is soft and can be wiped off with a bamboo knife, mainly caused by impurities; the other is that the hair is initially filamentous, and then slowly distributed in a strip shape. Can not be wiped off with a bamboo knife, the reason for its production is very complicated, involving ink, plate making, ambient temperature, humidity, scraper hardness and other aspects, specific problems need to be analyzed and processed. In general, there are probably the following aspects:
a. Edition roller aspect. The surface finish of the roller is not good, the hardness of the chrome plating on the surface of the roller is not enough, the plate roller is too smooth, and it is easy to produce without lubrication.
b. In terms of ink. The fineness of the ink is not enough, the pigment particles are too large, and the particulate impurities are mixed during the use of the ink; the dilution of the ink is not standardized, and the solvent impact phenomenon is generated; the antistatic property of the ink is poor, and the lubricating property of the ink is poor. The use of high hardness pigments produces lines.
c. Environmental aspects. The temperature, humidity and cleanliness of the air in the pressroom can also be affected.
d. Scraper. A hard scraper produces more line marks than a soft scraper. In addition, if the scraper line marks are not processed in time, a large bundle of scraper line marks will be generated around the line marks as the blade swings back and forth.
1 When loading the knife, it must be flat and careful. Before installing the knife, check whether the scraper blade has a gap. After the knife is installed, it must be carefully ground. If there is a wire in the printing process, it must be stopped and carefully ground. It is strictly forbidden to mix the oil of the knife into the ink.
2 It is necessary to control the environment and reduce dust in order to eliminate the fault. The color printing environment should be kept as closed as possible, and the air filter can be installed and checked for dust content. Otherwise, it is difficult to produce high quality products.
3 The wire caused by the plate roller generally appears in the shallow part of the mesh, for example, the plate is rough, the gradient is excessively uneven, and the mesh depth is not suitable. Generally, it should be treated by grinding with metallographic sandpaper. Pay attention to the uniform force when grinding the plate, especially if it is serious, return it to the plate making factory.
4 reduce the viscosity of the ink, such as too much viscosity, the plate ink drying too fast, relatively increasing the friction between the plate roller and the blade, making it difficult for the blade to scrape the plate ink to form the wire.
5 If the knife wire is caused by ink, it is generally caused by garbage or ink dissolving in the ink. Filter ink should be used to re-select solvent with strong solubility or change ink.
First of all: the amount of ink added to the ink tray is required to be small each time to keep adding new ink frequently.