EP1048461B1 - Method for register control in coincident printing of several sections colours - Google Patents

Description

When overprinting several partial colors, the relative position of the partial images must be can be adjusted to each other in order to obtain a pressure suitable for the register. at Rotary printing machines are provided with register setting devices with which the position of one of the partial images in the printing direction and across the printing direction Moving and twisting can be changed. It is known to be in contrast Specify rich color as the reference color and the location of all other drawing files used inks relative to the reference color. To monitor the The status of the partial images are used for crosses that are visually viewed with a cross-mark reader or register marks, whose reflection values with a photoelectric sensor be included. The relative position of the Drawing files are kept independent of each other. Another option is there in defining a reference position regardless of one of the part colors, all Drawing files can be set in relation to the reference position. In this case applies none of the part colors as reference color.

It is also known to change only parts of a sub-picture in their position, to compensate for errors caused by round printing, narrow and wide printing. suitable Actuators cause a deformation of the printing plate producing a partial image.

During a setup phase, the actuating amounts of the register setting devices are relatively large. In order to generate as few misprints as possible, the control and Control devices for register setting speed-optimized. Corresponding The position of a partial color moves according to the timing of the control and actuators Reference to its target position, with a certain overshoot around the target position can do what disappears after a period of time.

If the position of the print image in relation to the edges of the substrate is to be changed, then all partial colors are shifted by the same amount and in the same direction or twisted. Here, a reference color can serve as the lead color, the change in position of which other partial colors somewhat delayed due to the effect of a control device consequences.

Especially with web offset printing machines there is a partial Wrapping a blanket cylinder with the paper web. This is due to cohesion the printing ink placed on the paper web and remaining on the rubber blanket. Is this Rubber blanket attached in a channel of the blanket cylinder, then the Suddenly the paper web is wrapped around the channel edge canceled. One speaks of a so-called canal strike, which causes Paper particles are released from the web and lie down on the rubber blanket. The paper particles are initially deposited in non-printing areas of the Surface of the rubber blanket and settles in the dirt with increasing printing areas. As a result, there is a reduction in printing Dots, which leads to a change in color in the printed image. That can be limited Measures can be countered by increasing the ink supply. The disadvantage here is that it after a blanket washing process there is coloring instability because it is temporary there is too much color in the printing unit. Systems that control the ink supply according to a Automatically reduce cleaning process are imperfect because of the Color reductions are difficult to calculate due to a large number of influencing factors. The Problems associated with channel runout occur in particular Web presses designed for double-sided printing on a web are.

The object of the invention is to provide a method for register control To develop overprint of several partial colors, which is the number of Reduced cleaning processes and which improves print quality.

The solution to the problem arises with a method which determines the characteristics Claim 1 has.

The ongoing change in the position of the drawing files results in a cleaning effect for the pressure transmission material, especially for rubber blankets from Offset presses. The change in position means that other areas of the Print transfer material are used in the ink transfer. Contamination is caused by the print transfer material during ink transfer detached and transferred with the printing ink to the substrate. With the help of Register setting elements are the position of all part colors in the printing direction and across to do this, e.g. B. amounts between 0.01 and 0.03 mm in a cycle of approx. 2-6 minutes, changed. The amounts of the adjustment are significantly larger than the grid width of the Pixels. If the position of the drawing files is slowly changing, then that is it is possible for rotary printing presses with a color register control, circumferential and To adjust the side register of a base color in a given flow chart, whereby the other partial colors follow the change of position of the base color relatively quickly, so that there are no register deviations visible to the human eye. The span The changes in position lie within the range of the permissible tolerances for the position of the Print image in relation to the substrate edges.

In the event of cyclical changes in the position of the drawing files, the cycle duration can be based on the period mechanical natural vibrations of the printing press can be matched. The The amplitude, the stroke and the curve of the cyclical changes in position can be based on the grid width and grid angle of the drawing files are coordinated. It is the same possible the movements of the drawing files with regard to the mechanical To optimize the construction of an elastic cylinder lift. The movements can vary according to the distance and direction of textile fibers of the elevator and / or align according to the pattern of a structured elevator surface. The Speed profile of the motion sequences can change in the printing direction and across distinguish clearly. For example, the changes in position of a partial image in Print direction is faster than across the print direction.

Fig. 1: ein Schema einer Vorrichtung zur Registereinstellung,

Fig. 2: ein Schema einer Anordnung zur Registersteuerung, und

Fig. 3 - 6: Schemata zur Lageveränderung eines Teilbildes.

The invention will be explained in more detail below on the basis of an exemplary embodiment, in which:

1: a diagram of a device for register setting,

2: a diagram of an arrangement for register control, and

3 - 6: Schemes for changing the position of a partial image.

In Fig. 1 the last printing unit of a printing press for printing is highly schematized represented on a web 1. When conveying the web 1 in the pressure gap 2 between one Transfer cylinder 3 and a printing cylinder 4 is corresponding to a field Printing ink placed on web 1. The drawing file is a color separation on a printing form 5 generated, which is located on a forme cylinder 6, which is in rolling contact with a blanket 7 of the transfer cylinder 3 is.

The partial image includes an actual usable print image 8 as well Register marks 9. The position of the partial image on the web 1 is in the printing direction x and in Page direction y is set so that the drawing is exactly the same as the previously printed one Drawing files is available. On web 1, there are at the exit of the printing press high quality print images, the register accuracy of no further corrections requirement. To set the register are on each printing unit

Register setting devices 10, 11 are provided. When the register setting device 10 is actuated, the forme cylinder 6 and the printing form 5 are displaced in the lateral direction y. There is an equal displacement of the partial image on the web 1 in the lateral direction y. When the register setting device 11 is actuated, the phase position of the forme cylinder 6 and the printing form 5 is set in relation to the phase position of the transfer cylinder 3. There is a shift of the partial image in the printing direction x. The register setting devices 10, 11 are connected to a control and regulating device 12. The web 1 is scanned with a photoelectric detector 13 along a line 14 which extends in the pressure direction x and d _r the register marks 9, 15, 16 of all the color separations are printed. With the help of the detector 13, the positions of all partial images on the web 1 can be detected. The detector 13 supplies the actual value signals for the register deviations r _u , r, in the circumferential and lateral directions to the control and regulating device 12.

As shown in more detail in FIG. 2, the control and regulating device 12 contains a setpoint generator 17, a comparator 18 and a control element 19 for each of the printing inks. The actual value signals r _u , r _s are compared in the comparator 18 with setpoint signals w _u , w _{s of} the setpoint generator 17 compared. Control variables 19 s _s , s _{u are} formed in the control element from the comparison signals _and are supplied to the register setting devices 10, 11.

The setpoint signals w _u , w _s for a base color are subject to ongoing long-period changes, the actual value signals r _u , r _{s of} the base color and the other partial images quickly following these changes. The position of the partial image of the base color on the web 1 thus changes in accordance with the vector diagrams shown in FIGS. 3-6. The numbers entered in FIGS. 3-6 describe the sequence of the displacements in the xy direction. The displacements are in the range of 0.01-0.03 mm, whereby a cycle is completed in a period of 2-6 minutes. The displacement ensures that always other areas of the rubber blanket 7 are color-guiding, whereby dirt accumulated on the rubber blanket 7 is transported away via the color and the material of the web 1.

According to FIG. 3, the register of the standard color and the other colors carries out one rectangular movement. As shown in Fig. 4 or 5, there is the possibility to provide two or four rectangular motion cycles by one common position 20. The variant shown in FIG. 6 is concerned a back and forth displacement starting from a starting point 20. The displacements in the printing direction x and in the lateral direction y can be different run fast. The displacements can run along curved paths. It It is possible to change the shifting sequences for different subjects to be printed to design differently. For subjects that tend to form moiré or for Printing machines whose mechanical vibrations lead to cyclical register deviations can lead to the displacement processes in terms of phase, frequency and amplitude be dimensioned according to these phenomena. In the tax and Control device 12 can be provided with a plurality of selectable displacement processes become.

For presses that have a circumference and page register setting Allow skew register adjustment, the shifts described above can still can be combined with synchronous rotations.

LIST OF REFERENCE NUMBERS

1

train

2

nip

3

transfer cylinder

4

pressure cylinder

5

printing form

6

form cylinder

7

blanket

8th

print image

9

register marks

10, 11

Registereinstellvorrichtung

12

Control and regulating device

13

detector

14

line

15, 16

register marks

17

Setpoint generator

18

comparator

19

control element

20

starting point

Claims (3)

1. Method of register control when overprinting a number of colour separations, wherein register adjusting devices are used to adjust the position of the partial images generated on a printing stock by means of the colour separations so that the partial images are in register with respect to each other by register adjusting devices,
   characterized in that the position of all the partial images (8) on the printing stock (1) are continuously changed simultaneously by the same amount and in the same direction.
2. Method according to claim 1,
   characterized in that the changes are periodical and that the duration of a period is substantially longer than the duration of a printing cycle.
3. Method according to claim 1,
   characterized in that during cyclic printing, the frequency of the changes is not identical with the natural frequency and its harmonic vibrations of the printing press used.

Images