There are many quality problems with gravure printing on plastic films. One of the most common faults is the creation of a knife line. The production of knife lines causes the products to be scrapped, which can easily cause economic losses. As a printing company engaged in flexible packaging, it is extremely necessary to analyze and summarize the causes, and find the corresponding solutions, which will ultimately reduce the failure of the knife line to the lowest point.
There are many forms of knife-line production, and the following failure phenomena are analyzed for reference. In actual production, the higher the viscosity of the ink, the easier it is to produce a knife line during printing. This type of knife line generally exhibits two forms on the printed product. The first type of knife line is a fine, streamlined shape, which generally does not drag too long. Instead, it appears intermittently on the printed product. The starting point of the micro flow-shaped knife line is mostly close to the printing pattern, and the knife line is used. The starting point is generally larger than the end. If we do not observe it carefully in actual production, this tiny streamlined knife line can easily be ignored. This type of knife line is the root cause of quality accidents and must be taken seriously.
There are several ways to solve this streamlined knife line. The following are commonly used methods for printing staff:
1, will be a width of 5cm, length 15cm. The 140cm thick soft plastic sheet is smooth and smooth. When the knife line is lightly picked, under normal circumstances, this tiny streamlined knife line will be improved.
2, the most fundamental solution is to add a suitable amount of suitable solvent to the ink to reduce the viscosity of the ink. After the viscosity of the ink is reduced, the fine streamlined knife line will generally be eliminated. This is because the viscosity of the ink after the addition of the solvent is reduced, and the fine streamlined knife line is also related to the deterioration of the fluidity, which must be noted.
The second type of cutting line is the starting point of the printed pattern, but the knife lines are concentrated, and they are relatively coarse; they appear regularly in the same position of the printed product, and often continue to the next color. This type of knife line is easily found. The reason for this type of knife line is that the viscosity of the ink is too high, the printing plate's Internet point is poorly transferred, and the internal additives of the ink are destroyed with the change of the ambient temperature. Especially when the temperature is too high, a thin layer of ink will form on the surface. The dry solid layer takes a long time to build up the ink layer between the printing plate and the doctor blade to lift the squeegee upwards to produce such a knife line.
The solution to this type of knife line is to first adjust the squeegee angle. Under normal circumstances, the angle between the squeegee and the plate is 60, but sometimes the angle between the squeegee and the plate can be increased to about 65. This increases the pressure of the squeegee knife accordingly. At the same time, an appropriate amount of additives or solvents are added to the high viscosity ink to reduce the viscosity of the ink and increase the fluidity of the ink. When the solvent is added, the ink should be stirred along with the direction of the solvent. Another solution is to place an agitating roller in the ink tank. As the drum rotates, the agitating roller rotates accordingly, preventing the formation of a layer on the surface of the ink, which is also a method of reducing the generation of the cutting line.