Production and Exclusion of "Ghost" Phenomenon in Newspaper Printing Production

People who often read newspapers often find one or more thin lines that are significantly shallower than the printed text on some large-format pictures or textured strips in newspapers. This is called “ghosting”. Most of them are "missing ghosts." Ghost shadows refer to imprints or shadows of unknown origin.
Due to the timeliness of the newspapers, their strong political nature, short production cycle, and fast printing speed, once the phenomenon of “ghosting” occurs, the printing quality will be seriously affected and raw materials will be wasted. Less often it has an impact on the image of individuals and companies, and it causes political accidents. In order to truly understand the causes of the “imminent lack of ink”, it is necessary to understand the ink supply system composition of the printing press and the ink transfer mechanism.
1. The function of the ink supply system for printing presses The ink supply systems for newspaper turnaround machines and general sheetfed offset presses are composed of ink fountains, ink fountain rollers, ink transfer rollers, ink fountain rollers, and ink rollers. Sheetfed offset presses generally have 20 to 26 ink rollers. Rotary presses generally have only 7 to 11 ink rollers due to their high speed. If the ink supply speed cannot keep up, it will result in insufficient supply of required ink. The tasks of the ink supply system are simply two tasks: First, the ink from the ink fountain is quickly and evenly beaten by the ink roller; secondly, the ink roller is completely uniform with respect to the printing plate for each rotation of the printing plate. The right amount of ink.
As we all know, to make ink transfer well, the following conditions must be met:
1) The ink layer breaks in the middle between two mutually contacting ink delivery member surfaces.
2) Compression deformation occurs at one of the two transfer surfaces in contact with each other to ensure reliable contact between the ink molecules and the transfer surface. In the ink printing system of a newspaper printing press, the material of the ink transfer roller is required to have good ink-receptive performance, and the viscosity of the printing ink should be appropriate so as to ensure that the ink layer breaks in the middle thereof, and the soft roller and the hard roller are also required to be interposed. The setting is such that there is a reliable and ideal contact between the ink and the transmission member.
2. “Ghosting” Phenomenon Generation and Solution Based on experience and analysis of newspapers, there are mainly the following reasons for ghosting:
1) Poor Pressure Debugging The printing pressure and the contact pressure between the various ink rollers are not in the best printing state, resulting in a partial lack of ink and a "ghosting". Each ink roller requires good contact between each other to ensure the normal ink transmission, can not be too light or too heavy. According to general principles, the solid lines on the layout are not easy to produce "ghosting", but due to the improper debugging of the pressure between the ink rollers, affecting the normal ink volume transmission and water supply, it will also produce "ghosting" phenomenon. As long as the pressure is readjusted to ensure the smooth and uniform delivery of ink, the "ghosting" phenomenon can be eliminated. However, if the printing pressure is too light, there will be local hair blemishes in the prints, and water ripples will appear in serious cases.
2) The wear of the roller gear and the bearing gear The journal of the printer drum shaft is equipped with a helical gear to transmit power and precise positioning. Due to the high speed and long working time of the printer, the wear is naturally serious, and it is easy to cause the gear meshing gap to be too large. This causes the vertical drums to slip together and the contact between the gears is slightly misaligned, causing “ghosting”. The solution to this problem is to replace the gears and bearings; reduce the center distance of the roller and narrow the roller gap.
3) The rubber blanket and the printing plate do not stretch tightly without tensioning the rubber blanket, causing the rubber roller to be reset in time after being pressed or to be skewed when the blanket is cut, thereby causing “ghosting”. Plates can cause "ghosting" due to inaccurate work. Carefully check in the work, these failures can basically be ruled out.
4) newspaper layout design to be improved by thick solid lines, the area of ​​the isolated lines or decorative lines to design the layout, these lines are perpendicular to the direction of the printer ink roller, and the lines on both sides of the picture or perpendicular to the ink roller Shallow textured strips, then on these textured strips are prone to "ghosting." The reason is that the thick solid lines in the printing, the local consumption of ink is large, and the lines are often on both sides of the blank part. Due to the structural characteristics of the printing press, the local ink roller could not timely replenish the required ink in time, causing a "ghosting" phenomenon. As long as we are familiar with the above principles and perform correct operations, we can reduce the occurrence of "ghosting."