Newspaper printing company's cost control

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 "evil 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 role of printing ink supply system

The ink supply systems for newspaper web presses and general sheet-fed offset presses are composed of ink fountains, ink fountain rollers, ink transfer rollers, ink fountain rollers, and ink fountain 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 and solutions

Based on experience and analysis of newspapers, ghosting mainly has the following reasons:

1) Poor pressure adjustment

The printing pressure and the contact pressure between the various ink rollers are not in the optimum printing state, causing a partial lack of ink and forming a "ghost image." 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) Wear of roller gear and 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 blanket and plate are not tightened

The blanket is not stretched tightly, causing the rubber cylinder to be reset in time after being pressed or to be skewed when the blanket is cut, resulting in "ghosting." Plates can cause "ghosting" due to inaccurate work. Carefully check in the work, these failures can basically be ruled out.

4) newspaper layout needs to be improved

The layout is designed with thick solid lines, isolated lines or decorative lines. These lines are perpendicular to the direction of the printer's ink roller, and the lines have pictures on both sides or shallower textured lines that are perpendicular to the roller. Then on these textured strips, it is easy to produce "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."

Reprinted from: Guangzhou Printing Network