Installation and commissioning of offset presses and related requirements

After the offset printing machine is installed, it is necessary to conduct inspection and acceptance. The operator of the offset printing machine mainly checks its printing pressure and overprinting conditions. Acceptance is a very meticulous task and you must not act sloppy so as not to cause trouble.

A flat screen test and adjustment

Test printing flat-screen version of the printing film requirements: 175 lines of 50% flat screen (50%), before the print version must first use a density meter to measure the film's mouth, middle, three points of the density of the tip, confirm the film itself density difference After the printing plate is well dried, the densities of the three points on the PS plate are measured by a density meter. The dot density on the debugging sample sheet is finally measured, and the density difference of the same page dot is controlled within a range of 0.08. Prerequisites for measuring, observing, and calculating dot gain values; field density must be 1.5-1.6 (blue ink), because under the same conditions, the thinner the ink layer, the smaller the dot gain value, the thicker the ink layer, the larger the dot gain value. Big.

Ink screen printing usually uses red ink or blue ink. In the same flatness situation, red ink is more dazzling, but it is easy to reflect problems. The requirements for flat screen test are: no streak (black streaks, white streaks), The outlets are clean, firm, and clear. The expanded value of the outlets is controlled within 12%, the density difference between the same pages is controlled within 0.08, and the ground bar is placed in the middle of the flat screen version. In order to measure the field density, see Figure 10-3.

(Figure 10-3 flat network diagram)

Before the flat screen printing test, the center and pad of the three rollers are first adjusted to the standard state according to the requirements of the operating instructions, and the water and ink rollers are adjusted to the standard state (proved on the ink road map), otherwise it is difficult to print. Ideal test sample.

Second field test

The center distance of the three rollers and the adjustment requirements of water and ink roller are the same as those of the printing screen plate. The printing site requires three sides to leave the white edge and drop the water roller for printing. The use of blue ink printing, the advantages of the blue ink is not dazzling, and the density requirement is 1.5- Between 1.6 and the quality requirements, there are no white streaks and black streaks, and the same page density difference is within 0.08.

Triple Speed ​​Overprint Inspection and Adjustment

The purpose of all-overprinting is to check the stable operation of the positioning system. For high-speed offset presses, the first printing speed is 7,000 sheets/hour, and then 9,000 sheets/hour, 11,000 sheets/hour, and 13,000 sheets/hour are used respectively. Speed ​​overprint, overprint content: use full version of mm grid, because in the all-in-one set of printing, regardless of the size of the direction or direction, slightly inaccurate, the density value immediately increased to form a partial dark, without the use of a magnifying glass, naked eye Can also distinguish. See Figure 10-4.

(Figure 10-4 mm grid)

Four color test inspection and requirements

There are many varieties of color test plates, and the plants are not consistent, but the test content generally includes the following aspects: the density of the field, the exposure of the printing plate, the ghost of the dots, and the gray balance. Color test quality requirements:

(1) The four-color field density value cannot be lower than the standard value.

(2) Ghosting in the signal stripe The ghosting phenomenon cannot occur within the test segment, because in the test flat screen or in the field, all are monochrome printing, there is no transfer ghost problem, and the color test is a four-color group. Or the units above the four-color group are pressed at the same time for printing. The impression accuracy of the impression cylinder and transfer cylinder of each unit is slightly poor, and ghosting may occur in the imprinting. Therefore, the signal strip must be placed on the trailing area of ​​the trial printing plate. .
(3) Place a circle of millimeters (four colors) on the edge of the image of the trial printing plate to check the accuracy of four-color overprinting and check whether there is a fantail phenomenon in the machine.

(4) Compare the printed test sample with the manuscript to observe the contrast, that is, where the deep place is deep, the light place should be light, and the contrast must be opened.

(5) After trial printing of a batch of products, quality requirements must reach high quality products, and the entire commissioning work will be completed.