[Knowledge sharing] How to eliminate offset ghosts?
During the offset printing process, the "phantom" failure that appears on the continuously printed products is called "ghosting". In the actual production process, there are many factors that lead to the appearance of "ghost images".
1. Types of "ghost"
In general, "ghost" can be divided into mechanical "ghost" and craft "ghost". The mechanical "ghost image" is caused by mechanical action, which is mainly affected by printing pressure, ink roller, printing plate and other factors. The process "ghost image" is due to the chemical change of the ink during the printing process. Such "ghost image" is greatly affected by the production environment.
According to the positive and negative images of printed pictures, "ghost images" can be divided into positive images "ghost images" and negative images "ghost images". The darker part of the pattern of the printed product is called the positive image, and the extension in the circumferential direction forms a "shadow" that is lighter in color than the normal image, which is called the "ghost image" of the positive image, as shown in Figure 1a; The lighter part of the pattern of the product itself is called the negative image, and the "shadow" that is darker in color than the negative image formed by the extension in the circumferential direction is the so-called negative image "ghost image".
2. The formation conditions of "ghost"
The unreasonable layout design or improper adjustment of the printing press during offset printing is the main reason for the appearance of "ghost images" in the printed products, specifically:
① There is a pattern or text with a large amount of ink required at the head of the printing plate;
② There is a pattern with large ink demand and large area at the tail of the printing plate;
③ The distance between the pattern portion in the head and tail direction of the printing plate and the solid portion is just a multiple relationship with the diameter of the inking roller.
Offset "ghost" is a kind of avoidable failure, which focuses on prevention and avoids such failures.
ISGO has an experienced team of professional designers. Designers will design a suitable and personalized product image according to the different materials, structural differences, shape characteristics, and size requirements of the printed products in combination with the customer's brand culture. When designing and typesetting, the layout should be rationally designed. The proper layout arrangement can ensure that the grinding roller has sufficient inking time to balance the ink amount of the entire page, and technically reduce the appearance of ghosts.
Of course, you can also start from the following aspects to avoid the appearance of "ghost":
(1) Adjust the amount of ink supply corresponding to the "ghost" area.
(2) Increase the amount of tandem roller tandem. If the ink roller in the ink supply system can not guarantee the uniformity of the ink layer on the ink roller, "ghosting" will also occur. Therefore, it is possible to increase the momentum of the inking roller to avoid the appearance of "ghosting".
(3) Adjust the pressure. In order to avoid such "ghosting", the operator should adjust the pressure between the ink rollers in the ink supply system to the best state.
(4) Check whether the blanket is tight, the plate is tight, and the roller gear is worn.
For details, please call for consultation and technical discussion. Esko Technology, a professional one-stop curved printing service, solves printing problems for you, so that you have a perfect printed product.
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