Some discussion about the problem of "ghost" (Figure)

(This article is the exclusive contract draft of Bisheng.com. It is strictly prohibited to reprint.

There is a very hot topic on our forum, that is, the problem of "ghosts". This topic has been discussed for several months, but until now it is still a problem with many opinions on our forum. What do these questions include? What are the characteristics of ghosts? How do ghosts come about? What methods can be used to effectively avoid ghosts and so on. Let's start our introduction with these questions.

What is a ghost?
This is a matter of defining norms. If this definition is inaccurate or even wrong, then there is no discussion of ghosts. The concept of ghosts comes from abroad. The English word is GHOST, which means ghosts. It may be that people who initially found "ghosts" on printed materials think that the reason for the appearance of ghosts is really incredible. Named after the meaning.

Picture a is the pattern we want to print when printing. The position of "ABC" is in the direction of the mouth, first contact with the ink, and the position of the red solid is in the direction of dragging relative to the text "ABC". When the distance between the text part and the solid part (the distance marked by the blue arrow in Figure b) is just within the diameter range of the ink roller, it is likely that the effect of Figure b will appear after the printing process, that is, a A light imprint (marked by the green arrow in Figure b). Of course, this imprint is what we do not want to get. We call this imprint a ghost.

The appearance of ghosts requires several important prerequisites: (1) There are patterns or texts that require a large amount of ink in the direction of the mouth, which is the basis for the appearance of ghosts; (2) There is ink required in the trailing part A pattern with a large amount and a relatively large area is a carrier of ghosts; (3) The distance between the pattern part in the mouth direction and the solid part (or the large-area graphic part with heavy ink color) is just a multiple of the diameter of the inking roller relationship. (4) If the above conditions are met, ghosts may appear in the printing process, and of course, it may not appear.

How did ghosts come about?
In fact, the reason for ghosts is not very complicated. Knowing the reasons for ghosts, we will find that the appearance of ghosts is not incredible.
The pattern of the gripper part first contacts the ink roller, which means that the ink roller first supplies ink to the pattern of the gripper part. If the ink demand of the gripper part is large, it will leave a deep Ink latent image. After the platen roller has finished supplying ink to the image part of the gripper direction (as shown in ABC in Figure a), it turns back and begins to replenish the ink from the ink supply ink path. However, when the ink amount of the previous gripper part is compared Large, that is, when the shallow shadow of the ink layer left on the platen roller is relatively large, sometimes the ink supply cannot fill the latent image part. Therefore, when the ink roller continues to rotate to the next circle to supply ink to a large area in the direction of the mouth, this latent image will be expressed in a shallow way.
The same as shown in Figure c above is also a ghost situation, that is, the negative picture "ABC" of the mouth part is displayed in the form of a dark pattern on the picture of the dragging part.

How to deal with ghosts?
On machines without ghost elimination devices, we usually use the following methods:
1. The series momentum of the inking roller is increased;
2. Appropriately increase the pressure between the inking roller and the inking roller;
3. Add a solid bar to the place to absorb the extra ink in the blank space, which can solve a little problem;
From the above, we can see that the solution to ghosting is mainly from the design and improvement of the ink path. In fact, in many cases, ghosting cannot be completely solved from the adjustment of the printing mechanism. The more fundamental way is Fundamentally solved from design and plate making:
4. For some versions, if the bite is mostly a hollow picture, the middle to the back is slightly larger. This version can be turned around, and the bite can be solved by dragging the bite to solve the problem;
5. The design person should understand printing and solve from the design. For example, to avoid the graphics with large ink consumption (especially the graphics with a relatively small mouth area and the graphics with a relatively large area) correspond to the circumferential direction on the printing plate, or the design will use a smaller picture at the mouth The text and the larger area of â€‹â€‹the trailer are swapped.
6. In addition, when assembling the patterns on the printed matter, we should pay attention to avoid the distance between the two corresponding patterns exactly the same as the circumference of the printing ink roller on the printing machine.

We will also encounter such problems in actual printing. The situation shown in figure d is exactly the same as that of ghosts. It should also be avoided in the design. For example, the pattern block and the mouth of the trailing part of the illustration Part of the pattern blocks are swapped. It can effectively avoid the light-colored marks on the patterns shown in the figure. Once the situation shown in the figure appears, the processing scheme is the same as that for ghosting.

Are there any solutions for ghost images on modern, more advanced printing presses?
Heidelberg's printing presses introduced this year have made some fruitful adjustments to the ink mechanism of the printing presses for ghosting. For example, a separate ink inking mechanism has been added to the ink path of the CD102 series produced in recent years. This group of ink inking mechanisms can be used (dropped) or not (uplifted) by the operator according to production needs (mainly for ghosts). Since), this can make the ink film on the ink road more uniform in a short time. The agency has a very good role in improving the ghost problem.
On the new type of commercial rotation produced by Roland, the last two of the three form rollers can be axially serialized as needed, and the amount of serialization can be adjusted as needed. The device is also very effective for eliminating ghosts.
Domestic printing presses such as Beiren's N300 and BEIREN 104 series offset presses use pneumatically controlled axial movement of the plate roller to effectively eliminate the "ghosting" phenomenon.

Office Reception Desk

Office Reception Desk,Small Reception Desk,Modern Reception Desk,White Reception Desk

Feat Top International(China) CO.,LTD , https://www.nbfeattop.com