Review of lithographic printability (4)

Fourth, the suitability of printing technology

Lithography is very different from other formats. Other formats are mostly direct printing, that is, physical printing in which the printing plate is in direct contact with the paper or the printed body. The lithography is a chemical printing method using the principle of mutual exclusion of water and ink. Therefore, the applicability of other technologies is very different from other formats.

(1) Piles of paper: It should be noted that the cross-threads of the paper cannot be mixed and piled together. The entire pile must have a uniform thread flow. Otherwise, the color of the printed products will change due to the paper stretching, and the product quality will not be consistent.

(B) Ink balance: Since the lithographic printing machine must have a wet system to provide layout water. There are three types of systems: 1. Traditional water systems. 2. Semi-alcoholic system. 3. Continuous alcohol system. In order to make the distribution of water and ink on the printing plate average, it is necessary to make appropriate adjustments in order to obtain the best printing quality. When the ink is too much, it will cause layout pollution. Too little ink will make the line drawing not print or incomplete. Too much water will make the ink lighter, and vice versa, it will make the wireless part of the layout stained with ink. The alcohol system should pay attention to the composition and proportion of alcohol, and it also has a great influence on quality. Although these are very important tasks in lithographic printing, they can be handy if they actually work for a while.

(C) dusting: There are two kinds of dusting device: 1. Universal type. 2. Electrostatic type. Regardless of the type used, the main function is still to spray a layer of thin powder on the dry ink, so as to keep a little distance with the paper stacked on it, so as to avoid anti-printing. However, the quality of the powder and the amount of powder to be sprayed must be paid special attention. Poor quality or too much dusting will cause poor ink transfer, insufficient ink, and poor printing patterns during the next overprint or backside printing. Too little dusting will cause sticking of the upper and lower papers together, anti-printing and other phenomena.

(D) Indoor temperature, humidity and air flow: These are also major factors that affect the printing quality. Although it is not directly related to the technology, if the temperature, humidity and air flow are changed at the top and side of the printing press, it will make the layout. Water is not easy to control. In the past, because the cold air tuyere was on the upper left side of the printing press, the airflow on one side of the printing plate was larger than the other side. Therefore, on the large airflow side, the layout water was easier to dry and the ink-water balance operation was difficult to achieve. Printing technicians are very troubled and cannot get good print quality.