METHOD FOR EFFICIENT FAN-OUT CONTROL

Abstract

A printing method with fan-out control minimizes register deviations by using a computer. The method includes: printing a test print including various color separations, measuring the register deviations that have occurred relative to a reference color, calculating the absolute total of the register deviations of all color separations relative to one another, selecting at least one color separation to be adapted as a function of the calculated absolute total of all color separations, adapting the at least one selected color separation, and compensating for the register deviations that have occurred by creating and using at least one printing plate for the adapted at least one color separation.

Claims

1. A printing method with fan-out control for minimizing register deviations by using a computer, the method comprising the following steps: printing a test print of a layout including different color separations; measuring the register deviations that have occurred relative to a reference color; calculating an absolute total of the register deviations of all color separations relative to one another; selecting at least one color separation to be adapted as a function of the calculated absolute total of the register deviations of all color separations; adapting the at least one selected color separation; and compensating for the register deviations that have occurred by creating and using at least one printing plate for the adapted at least one color separation.

2. The method according to claim 1, which further comprises: calculating remaining register deviations of non-adapted color separations when the at least one adapted color separation is used; evaluating the remaining register deviations in terms of maximum acceptable tolerances; and implementing further measures if the remaining register deviations are outside of the maximum acceptable tolerances.

3. The method according to claim 2, which further comprises selecting and adapting at least one further color separation as the further measures.

4. The method according to claim 2, which further comprises predefining the maximum tolerances for remaining register deviations, by an operator or in an automated way by the computer.

5. The method according to claim 1, which further comprises predefining a maximum number of color separations to be adapted, by an operator or in an automated way by the computer.

6. The method according to claim 1, which further comprises selecting a color separation having the greatest deviation of the absolute total of the register deviations of all color separations relative to one another, as the at least one color separation being selected for adaptation.

7. The method according to claim 1, which further comprises implementing the adaptation of the selected at least one color separation by calculating a register deviation based on a difference of the register deviations of the at least one color separation and a mean value of all other color separations.

8. The method according to claim 1, which further comprises: using a reference color as one of the color separations; adapting only the color separation of the reference color; and choosing a new reference color among remaining color separations.

9. The method according to claim 1, which further comprises adapting at least two color separations being predefined by an operator or by a computer in an automated way.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0041] FIG. 1 is a schematic representation of the fan-out phenomenon;

[0042] FIG. 2 illustrates the result of a local register deviation; and

[0043] FIG. 3 is a flow chart of the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0044] Referring now to the figures of the drawings in detail and first, particularly, to FIG. 2 thereof, there are seen register deviations 4 to be compensated for, which are schematically indicated in the form of a register cross 3, that is used to measure the accuracy of the positions of individual color separations that are printed on top of each other. The example shown in FIG. 2 clearly indicates the deviations 4 that occur between the individual color separations if there are local register inaccuracies. FIG. 1 shows that the causes for such local register inaccuracies may be process-inherent deformations of the printing substrates. This figure clearly shows deforming forces 2 that occur in a direction transverse to the printing direction and deforming forces 1 that occur in the printing direction. However, since these deforming forces influence one another, there are resultant deformations in all directions 1 and 2. These deformations 1 and 2 need to be factored in to obtain high-quality prints. For this purpose, a control unit 12 may carry out a fan-out control method known from the prior art.

[0045] A preferred embodiment of the method of the invention for such fan-out control is shown diagrammatically in FIG. 3 and will be explained in more detail below based on an example.

[0046] The following table shows an example of a measured register deviation 5 without FOC (fan-out control).

TABLE-US-00001 Register Deviation Narrower/Wider [mm] Shorter/Longer [mm] Place Color AS MI BS AS MI BS EP Black 0.00 0.00 0.00 0.00 0.00 0.00 EP Cyan 0.11 0.05 0.01 0.14 0.05 0.09 EP Magenta 0.10 0.07 0.01 0.12 0.02 0.20 EP Yellow 0.07 0.07 0.05 0.15 0.01 0.20 SP Black 0.00 0.00 0.00 0.00 0.00 0.00 SP Cyan 0.05 0.06 0.04 0.05 0.06 0.09 SP Magenta 0.06 0.06 0.04 0.17 0.11 0.03 SP Yellow 0.07 0.07 0.06 0.17 0.10 0.07

[0047] The measured values are typical for register deviations in the transverse direction (narrower/wider) and in the circumferential direction (longer/shorter) caused by the corresponding deformations 1 and 2 at the end of printing (EP) and at the start of the printing (SP). The register deviations of the chromatic colors relative to one another are comparatively small but the deviations from the reference color black are considerable.

[0048] In accordance with the method of the prior art, a register correction is calculated for the chromatic colors using the FOC process and new plates are created. In general, that is done for all plates although black remains unchanged.

[0049] In contrast, the method of the invention now calculates the absolute total of the register deviations 6 in the transverse and circumferential directions between each color and all the other colors. The following values are the result:

TABLE-US-00002 Absolute Total of the Register Deviation Black Cyan Magenta Yellow Narrower/Wider Black 0.00 0.32 0.34 0.39 Cyan 0.32 0.00 0.04 0.17 Magenta 0.34 0.04 0.00 0.13 Yellow 0.39 0.17 0.13 0.00 Shorter/Longer Black 0.00 0.48 0.65 0.70 Cyan 0.48 0.00 0.39 0.36 Magenta 0.65 0.39 0.00 0.11 Yellow 0.70 0.36 0.11 0.00 Total [mm] Black 0.00 0.58 0.73 0.80 Cyan 0.58 0.00 0.39 0.40 Magenta 0.73 0.39 0.00 0.17 Yellow 0.80 0.40 0.17 0.00 2.11 1.37 1.29 1.37

[0050] Then a total deviation, for instance the Euclidean distance, is calculated from the transverse direction values and the circumferential direction values, and the total is calculated for every color. In the given example, black has a deviation value of 2.11 mm relative to the other colors whereas the values for cyan, magenta, and black are much lower: 1.37, 1.30 and 1.37 mm. The greatest improvement is achieved if new plates are calculated for the color separation that has the highest deviation value. Thus the recommendation for the FOC in accordance with the method of the invention is:

TABLE-US-00003 Desired Number of New Plates 7 Recommendation Color Separation 8 1 black 2 black and cyan or magenta 3 black, cyan, magenta 4 black, cyan, magenta, yellow

[0051] If only one color separation is to be recalculated and recreated, as is the case in the current example, it is ideally the black separation that is used. For this color separation 8, a register deviation is calculated on the basis of the difference of the register deviation of the black separation (in this case zero) and the mean value of all other color separations at every measuring point. The following register deviations are the result:

TABLE-US-00004 Register Deviation for FOC Narrower/Wider [mm] Shorter/Longer [mm] Place Color AS MI BS AS MI BS EP Black 0.09 0.06 0.01 0.14 0.02 0.16 EP Cyan EP Magenta EP Yellow SP Black 0.06 0.06 0.05 0.13 0.09 0.06 SP Cyan SP Magenta SP Yellow

[0052] These deviation values are used to create a FOC compensation printing plate 9 for black, with the following resultant register deviations 10 relative to black:

TABLE-US-00005 Remaining Register Deviation 10 Narrower/Wider [mm] Shorter/Longer [mm] Place Color AS MI BS AS MI BS EP Black 0.00 0.00 0.00 0.00 0.00 0.00 EP Cyan 0.02 0.01 0.02 0.00 0.03 0.07 EP Magenta 0.01 0.01 0.02 0.02 0.00 0.04 EP Yellow 0.02 0.01 0.04 0.01 0.03 0.04 SP Black 0.00 0.00 0.00 0.00 0.00 0.00 SP Cyan 0.01 0.00 0.01 0.08 0.03 0.03 SP Magenta 0.00 0.00 0.01 0.04 0.02 0.03 SP Yellow 0.01 0.01 0.01 0.04 0.01 0.01

[0053] A comparison between the reduced register deviations 10 that have been obtained by this measure and the initial register deviations 5 without FOC indicates that the register deviation is reduced considerably by calculating the register deviation in accordance with the method of the invention and creating only one printing forme 9 based on the recalculation.

[0054] In the present example, the maximum resultant register deviation 10 would be reduced from 0.2 mm to 0.08 mm. The mean register deviation drops from 0.06 mm to 0.018 mm.

[0055] Since this deviation meets the majority of quality requirements in terms of maximum acceptable register deviations 11 that occur in practice, maximum results are gained by minimum effort.

[0056] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: [0057] 1 deformation in the printing direction [0058] 2 deformation in a direction transverse to the printing direction [0059] 3 register cross [0060] 4 register deviation [0061] 5 measured register deviation [0062] 6 absolute total of all register deviations [0063] 7 maximum number of color separations to be adapted [0064] 8 color separation selected for adaptation [0065] 9 adapted color separation [0066] 10 remaining register deviation [0067] 11 maximum tolerated register deviation [0068] 12 control unit