Technical Field of the Invention

The invention relates to a register method and system for flexo printing machines.

Background of the Invention In order to be able to print cost-effectively, there is a need to start up the printing process promptly and to generate only minimum waste. A reduction of the setup time allows an earlier start of the printing process, which results on a longer printing time on which the printing machine is usable for the printing process. A prerequisite for this is a good register setting. It is known, that one can monitor the register results by using printed sample sheets. DE 195 48 253 discloses a system where the interpretation of the register marks is performed outside or inside the printing machine with help of sample sheets. EP 0 870 607 discloses a system where a print substrate web is monitored in a flexo printing machine. Further, there are known procedures to determine the position of an offset printing plate mounted on the cylinder with a measuring device. For example, DE 31 36 703 discloses a system, by which the actual position of each offset printing plate is determined followed by adjustments of rotational, transversal and diagonal register.

There are also known procedures to determine the position in the sheet feeder with a measuring device. For example, DE 10 2005 046 232 discloses a system where the actual position of the sheet alignment means is determined in addition to the printing plate positions.

By the two latter mentioned processes it is disadvantageous to flexo printing machines, that the flexibility of a flexo printing plate is not taken into account for the register setting.

The inks used for corrugated board flexo print will dry out on the plate within 15 to 20 minutes, i.e. it is very important that there is only a short period of time necessary from first ink application on the plate until continuous print production. By so-called inliner machines, i.e. a printing machine with downstream devices for die cutting and removal of waste, it is also necessary to adjust those downstream devices.

Starting from this prior art, the object of the invention is to overcome the mentioned disadvantages by providing a method according to claim 1 and a system according to claim 14. The dependent claims define preferred embodiments of the invention.

This problem is solved by a system, where the positions of the printing plates and the up- and downstream print substrate touching means are determined, the individual colour shades are detected and the results are presented to the operator and/or are directly influencing the machine control system. Brief Description of the Drawings

The following examples show further advantageous features and characteristics of the invention, which are described in more detail with reference to the representations. The exemplary representation describes the process in a flexo printing machine, which comprises a cutting device and where the register adjustments are performed manually. The invention also incorporates other machine configurations and machines with semi- or fully automatic register adjustment.

Shown is in:

Figure 1 Process sequence

Figure 2 Product with nominal dimensions, set values Figure 3 Evaluation areas

Figure 4 Presentation 5

Figure 5 Presentation in area by 18a, 18b

Figure 6 Modes of register adjustment

Embodiments of the Invention Figure 1 shows the sequence in accordance with the invention. In the preparation 1 for a new product, the nominal dimensions, the set values, are inputted or imported.

In the next Phase 2, a suitable presentation is prepared, in which the evaluation areas are defined. The determination of actual values 3 comprises position values and colour shades. The position values for the infeed contact stops, the register marks and die cutting knives are determined by optical sensors, e.g. cameras. These sensors can be selectively aimed at the evaluation areas, or automatically traversed in the axial cylinder direction in order to cover multiple evaluation areas. The position within the print cycle, e.g. determined by an incremental encoder on the first plate cylinder, may be used as reference. The colour shades will be determined preferably by optical sensors, e.g. cameras, above the respective ink container allocated to each printing unit.

In phase 4, the actual values and the set values are combined and the presentation is calculated. In phase 5, the results are provided to the machine operator.

Corrections 6 to the register adjustments are performed, at which signals 10 initiates a determination of new actual values 3.

When the comparison between actual and set values is within the desired tolerances, a proof print 7 is initiated. When the product check shows an immaculate result, the production 9 is started. Else, corrections 8 are made and a request 11 for a new proof print 7 is initiated.

The values of the corrections 8 can have an impact on the presentation 2 of the set values in a processed form 12, e.g. proportionately, through averaging or in another smoothed form. Figure 2 shows a product with nominal dimensions. Out of the dimensions of the infeed contact stops 13, 14a, 14b, the stop in the longitudinal register direction 13 is used as reference in this example. The dimensions for the register marks 17a to 20b and the die cutting knives 15, 16 are relating to the stops 13 and 14. Figure 3 shows the selected evaluation areas.

Figure 4 shows a display screen layout for the evaluation areas with exemplary actual values, i.e. sensor signals, e.g. camera images, for the respective evaluation elements. For the sake of clarity, only the register marks from one plate cylinder is shown. Figure 5 shows a presentation of the areas 18a, 18b with register marks 21, 22, 23, 24 from four plate cylinders. In the figure, the different line types represent the respectively different colour shades. The display of the register marks is performed in the colour shade allocated to the respective printing plate. The allocation is, in accordance with the invention, automatic by means of the formerly mentioned sensors. Figure 6 shows fundamental illustrations of modes of register adjustments,

25 : in longitudinal direction

26: Longitudinal elongation, whereas this outcome can be received also by a nonuniform peripheral speed

27: in lateral direction 28: lateral elongation

29: rotational direction, also called diagonal register

30: rhomboid

31 : rotational elongation

List of reference numerals 1 Product preparation

2 Preparation of presentation

3 Determination of actual values

4 Calculation of presentation

5 Provision of results 6 Corrections

7 Proof print

8 Corrections

9 Production

10 Signal

11 Request

12 Processed correction values

13 Infeed contact stops in circumferential direction 14a, 14b Infeed contact stops, sideways

15, 16 Cutting knives

17a, 17b Register mark position

18a, 18b Register mark position

19a, 19b Register mark position

20a, 20b Register mark position

21 , 22, 23 , 24 Register marks

25 Register setting: longitudinal direction

26 Register setting: longitudinal elongation

27 Register setting: lateral direction

28 Register setting: lateral elongation

29 Register setting: rotational direction

30 Register setting: rhomboid

31 Register setting: rotational elongation In an embodiment identified as "embodiment 1", a print substrate independent register system for the print substrate touching means of a printing machine, comprises at least the position detecting devices at two locations for printing media, and is characterized in that the thus determined relative position is utilized in order to reach an adequate register setting.

Embodiment 2. A method according to embodiment 1, characterized in that the print substrate touching means consists of a printing plate.

Embodiment 3. A method according to embodiment 2, characterized in that the printing plate is a flexographic plate. Embodiment 4. A method according to embodiment 1, characterized in that the position detecting devices operate by an optical process.

Embodiment 5. A method according to embodiment 4, characterized in that the optical process uses imaging means.

Embodiment 6. A method according to embodiment 5, characterized in that the imaging means uses cameras.

Embodiment 7. A method according to embodiment 5, characterized in that the imaging means are supported by intermittent illumination.

Embodiment 8. A method according to embodiment 1, characterized in that the print substrate touching means consists of pre- and post-processing devices. Embodiment 9. A method according to embodiment 8, characterized in that the preprocessing device is a sheet feeder.

Embodiment 10. A method according to embodiment 8, characterized in that the postprocessing device is a cutting device.

Embodiment 11. A method according to embodiment 1 , characterized in that the print substrate consists of corrugated cardboard.

Embodiment 12. A method according to embodiment 1, characterized in that the register setting includes at least one of the following possibilities, a. Position in the circumferential direction including irregularity within one cylinder revolution b. Position in the lateral direction c. Plate rotation d. Plate elongation in the circumferential direction e. Plate elongation in the diagonal direction

Embodiment 13. A method according to embodiment 1, characterized in that the presentation of a register mark is complemented by a color shade of the printing ink as determined by a sensor.