(1) Factors of paper flatness
The ideal paper should be smooth, flat and of uniform thickness on both sides, so that it can form a good contact with the flat surface (such as pad, blanket, printing plate, etc.). But in fact, most paper is not ideal, mainly manifested in: uneven thickness, uneven surface of the paper, can only touch one side of the printing plate; the surface of the paper is rough, only a small area of ​​discontinuous with the plate Contact is one of the factors that cause the ink on the paper to be untrue.
Usually, the paper with uneven surface but uniform thickness can be adjusted to make good contact with the printing plate by adjusting the printing pressure. However, if the uneven performance of the paper is poor, it cannot be adjusted in this way. However, if the paper is flat on one side, it can be lined with a soft pad to form a good contact with the printing plate. But these two methods will cause the paper itself to stretch or bend, and the required pressure is adjusted according to the amplitude, frequency, unevenness of the paper surface and the hardness of the paper.
(2) Factors of different inking on the paper surface
At present, the commonly used papers include coated paper, white card, gold card, silver card and glass card paper. At the same time, the gold card and silver card are divided into aluminum foil gold card, silver card and PE film gold card and silver card.
In addition to the influence of the flatness of the paper on the printing ink, the more important is that the amount of ink absorption of the material itself is also the main factor. For example, white card paper has much more ink absorption than gold card and silver card compared with gold card and silver card. However, compared with the gold and silver cards of compound aluminum foil, the ink absorption of the former is obviously larger than that of the gold and silver cards of compound PE film.
Due to the above paper factors, customers should provide accurate paper information when making a plate, so that the plate-making company can develop different plate-making processes according to different paper properties.
(3) Problems in information transmission
In the printing process, paper, ink, plate rollers, and printing machines are all suppliers of printing plants. A high-quality product must be their best match. No matter what problem occurs in a link, printing defects will be produced. Therefore, the cooperation and exchange of the four parties is very important. However, due to the large industry span and few opportunities for mutual communication in practical work, it is very difficult to solve unilaterally when printing comprehensive problems arise. For example, when our company makes a soft package for a customer, one of the big red blank words (English words, Chinese will be worse), the blank words after printing on the machine are significantly thinner than the sample. Look at our company's concave blank text slightly thicker than the sample. We analyzed with our customers and wanted to solve the problem by increasing the viscosity of the ink and reducing the printing pressure. The phenomenon of ink flutter after printing was obvious, and this phenomenon was eliminated after the ink formula was replaced again.
Another problem is that due to various factors, many manufacturers have blindly requested that the depth of the plate roller be deepened, so that the printing plate almost reaches the limit depth of electronic engraving. In fact, the deeper the plate roller is, the worse it is not conducive to high-speed printing, and the more likely it is that there are knife wires, blocking plates, and ink dragging on the edges of patterns.
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