Poor Ink Overprint

The multi-color machine completes the printing in a very short period of time, and the overprinting method of the ink is wet-on-wet. If the printing color sequence is not properly arranged, the ink overprinting rate will be greatly reduced. Therefore, according to the characteristics of the multi-color machine, when arranging its printing color sequence, the following basic principles should be followed:

(1) Arrange the printing color sequence according to the ink transparency. The ink color with lower transparency is printed first, and the ink color with higher transparency is printed later, which can improve the color rendering effect after ink overprinting.

(2) Arrange the printing color sequence according to the area of the printing plate. That is, the ink with a small area of the printing plate is printed first, and the ink with a large area of the graphic is printed later.

(3) Arrange the printing color sequence according to the ink viscosity. The ink with high viscosity is printed first, the ink with small viscosity is printed later, and the ink viscosity is reduced color by color. If the color ink with high viscosity must be printed in the next color group, the viscosity should be appropriately reduced with a detackifier first, otherwise there will be a reverse overprinting failure, that is, the phenomenon of ink color mixing. For example: when the gripper of the machine is worn and the black characters have ghosting faults, the color sequence can be adjusted, and the black ink can be arranged in the second, third or fourth color group for printing, but the viscosity of the black ink should be reduced in time.

(4) Arrange the printing color sequence according to the characteristics of the original. For example, when printing originals such as characters and colorful clouds mainly in warm tones, cyan should be placed in the previous color group, and magenta should be arranged at the back; when printing originals such as glaciers and snow scenes mainly in cool tones, magenta should be placed in the first color group. The previous color group, cyan is arranged in the back.

Ink-to-paper peeling tension problems lead to inaccurate overprinting

For a full-page large-volume printed product, the viscosity of the ink and the printing pressure must not be too large. Otherwise, once the paper is thin, it will be difficult for the paper to overcome the excessive printing peeling tension, resulting in inaccurate overprinting, paper curling, and even gripping. The teeth cannot peel off the paper from the blanket to complete the normal handover, resulting in the phenomenon that the paper is constantly torn and peeled. Measures can be taken to add a detackifier and reduce the printing pressure. After the peeling tension of the ink to the paper is greatly reduced, the production can naturally proceed normally.

The color rendering of the ink is dark

Among the commonly used three primary color inks, due to factors such as cost and price, different batches of inks have certain deviations in hue, such as medium yellow to red, magenta to yellow, and sky blue to red. Red or green, the color saturation is lower, and the grayscale is larger. At this time, you can analyze the original, grasp the most important color tone, choose the most suitable ink, and print the best effect.

Ink-induced "ghosting"

There are basically three forms of ghosting in offset ink printing:

1. Pattern ghosts;

2. Line ghosts;

3. Eraser or print-through afterimage.

The ghosts in the above 1 and 2 cases are caused by the ink roller system. The solutions are as follows:

(1) First, you must carefully check and adjust the correct pressure of the ink roller.

(2) Minimize the amount of water used in the layout.

(3) The ink release key must be adjusted more carefully to a small level of ghosting.

(4) Attempt to turn around for publishing or printing with a printing plate. Ghosting is most likely to appear at the back end of the layout and when there are darker, larger ink sticks. U-turn printing of the plate can alleviate the tendency of ghosting.

(5) The pendulum roller swing is adjusted to be large.

(6) Start the traversing ink roller. Most of the ink rollers of the new type of machine are designed to be able to move laterally left and right, and can be set to open 1 to 4, which can alleviate more than 80% of the ghost phenomenon.

(7) Change the ink supply state to the ink supply method of large turning angle and small opening. This will effectively improve ink leveling and reduce ghosting.

(8) Adjust the start time of the ink roller string. The ghost phenomenon can be alleviated by adjusting the relative time of the ink roller to the layout, and moving the dark ink position to a non-ghosting place.

(9) Add compensation print. Add compensating patches outside the print area. The compensation color block, color.