Automatic control of offset ink

The ink-jet mechanism of the offset printing press has always been the focus of research and development for major printer manufacturers. An excellent system will make ink control easier, and the preparation time for printing and the waste of printed materials will be greatly reduced. After years of development, the automatic control technology of ink volume has been very mature. Modern printing presses adopt automatic ink supply systems and have been fully acknowledged in the world. The ink volume automatic control system has become an offset printing machine purchase in developed countries. Is a must purchase component. This article aims to discuss the process of automatic control of ink volume and related principles.

Automatic supply of ink

1. Heidelberg sheetfed offset ink automatic supply system

Through the CIP3 file generated after the prepress RI P, the density of each ink zone on the print sheet (the Heidelberg multi-record La, b value) is converted from the center console to the ink amount of each color ink zone, and then the ink roller is on demand. Ink, so as to achieve the automatic supply of ink.

2. Manorland commercial rotary machine automatic ink supply system

Using the hydraulic principle to supply ink to the printing units. The advantage of this system is that it can supply ink on demand, it can be used for a long time, and the surface of the ink film does not dry out, and at the same time it can supply ink to multiple printing machines. The ink supply principle is shown in Fig. 3. The main components are the pump station piping system and the refilling system. The function of the pump station is to pump ink from the ink tank or ink tank. The function of the pipeline ink consumption metering system is to use a high-precision metering head to measure the ink consumption; the ink refill system is mainly to ensure the supply of ink.

Local ink supply

The ink supply system supplies ink to each printing unit through partition ink fountains, and the ink supply amount depends on the size of the area of ​​the graphic portion of the printing plate surface, that is, the area coverage of the graphic in accordance with the width of the plate ink region in the printing direction. To set each ink zone. In actual operation, the ink slit width of the ink fountain ink area is adjusted by changing the rotation angle of the ink fountain screw (based on the average value of the text area coverage), and the ink supply amount is controlled so as to adapt to the graphic image of the printing plate.

The presetting of the partition ink volume has undergone an evolution from manual adjustment to automatic adjustment. The manual adjustment is performed manually by the operator on the ink fountain, one unit is followed by one unit and the adjustment process is time consuming. In addition, the manual preset adjustment is the setting of the ink slit width by the operator based on the operation experience and the visual prediction of the ink amount in the ink area, and the adjustment accuracy is not high. Until the invention of the plate reader in 1982, substantial progress was made in reducing the preparation time for printing. With a plate reader, the ink demand of each ink zone of the printing plate can be automatically measured before loading, and the ink gap width of the ink fountain ink zone can be further controlled accordingly.

Heidelberg's CPC32-CIP3 is an example of a prepress, printing, and postpress digital workflow based on the CIP3 standard. The CPC32-CIP3 adopts the print production-specific data format PPF to transmit the presses' preset data, especially the preset data of the ink supply device.

With the promotion of JDF technology, the preset of ink volume becomes easier and more accurate: the data before printing can be directly downloaded to the printing press, and the printing press can automatically adjust the ink volume according to the graphic information before printing. Each ink zone has a servo-driven motor, and the console gets the data to be transmitted to its motor. The rotation of the motor is used to adjust the gap between the ink fountain blade and the ink fountain roller to achieve local adjustment of ink volume.

Overall ink size adjustment

According to the actual situation of printed graphics, the overall change in the amount of ink. For offset ink fountain roller offset press is to adjust the ink fountain roller by changing the angle of the ink to change the size, then the overall adjustment of the amount of ink must be artificially controlled, according to the overall situation of printing graphics to determine the ink fountain roll angle; for continuous The rotating ink fountain roller can be adjusted by changing the rotation speed of the ink fountain roller. The rotating power of the ink fountain roller can be driven from the main motor or from a separate servo motor. The control of the total ink volume changes the ink supply on the one hand in accordance with changes in the speed of the host machine, and on the other hand, individual ink volume adjustments can be made based on the actual printed image and text. Modern offset presses basically use a continuously rotating ink fountain roller structure to achieve automatic ink supply.