Gravure plate failure analysis and troubleshooting: Inaccurate or excessive ink
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(1) Paper flatness factor
Ideally, both sides of the paper should be smooth, flat, and uniform in thickness so that they make good contact with the flat surface of the contact (such as liners, blankets, plates, etc.). But in fact, most papers are not ideal, mainly in the following: the thickness is uneven, the paper surface is undulating, and it can only touch one side of the printing plate; the paper surface is rough and can only have a small area of discontinuity with the printing plate. Contact is one of the factors that cause the paper to be inaccurate.
Typically, paper with a undulating surface but a uniform thickness can be brought into good contact with the printing plate by adjusting the printing pressure. However, if the uneven paper is poor in compression, it cannot be adjusted in this way. However, if the paper is flat on one side, it can be lined with a cushion to make good contact with the plate. However, both of these methods cause the paper itself to stretch or bend, and the required pressure is adjusted according to the amplitude, frequency, unevenness of the surface of the paper, and the hardness of the paper.
(2) Factors of different ink on the surface of the paper
Currently used papers include coated paper, white cardboard, gold, silver, and glass cardboard. At the same time, gold and silver cards are divided into aluminum foil gold, silver, and PE film gold and silver cards.
In addition to the influence of the flatness of the paper on the printing ink, it is more important that the amount of ink absorbed by the material itself is also the main factor. If white cardboard is compared with gold and silver cards, the amount of ink absorbed by white cardboard is much larger than that of gold and silver cards. However, the gold or silver card of the composite aluminum foil is significantly larger than the gold card and the silver card of the composite PE film.
Due to the above paper factors, customers should provide accurate paper information during plate making, so that the plate making company can make different plate making processes according to different paper properties.
(3) Problems in information transmission
In the printing process, paper, ink, plate roll, and printing machine are all suppliers of printing factories. A high-quality product must be the best combination of them. No matter what happens in that part, it will produce printing defective products. Therefore, the cooperation and exchange of the Quartet is very important. However, in actual work, due to the large span of the industry and the lack of opportunities for mutual communication, it is very difficult to solve the comprehensive problems in printing only by unilateral solution. For example, when our company makes a soft bag for a customer, one of the big red blanks (English word, Chinese will be worse), the blank word after printing on the machine is obviously thinner than the sample. Look at my company's concave blank text is slightly thicker than the sample. We analyzed with the customer, and wanted to improve the viscosity of the ink and reduce the printing pressure. The phenomenon of ink spilling after printing was obvious. This phenomenon was eliminated after the ink formulation was replaced.
Another problem, due to various factors, many manufacturers have repeatedly requested to deepen the depth of the plate, so that the plate almost reaches the extreme depth of electronic engraving. In fact, the deeper the plate roll is, the more unfavorable it is for high-speed printing, and the more likely it is to cause the phenomenon of knife wire, blockage, and pattern edge dragging.