Method for color measurement in printing presses

Abstract

A color measurement on printed materials produced by a printing press is performed by at least a first color measuring device installed in the printing press and at least a second color measuring device. A signal is output by the first color measuring device in the printing press when the measured color values registered on the printing materials are located within a predefined tolerance limit for a predefined period and that, after the signal has been output, a color measurement on one of the printed materials thus produced is performed with the second color measuring device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The sole FIGURE shows a schematic side view of a sheetfed printing press having a first and a second color measuring device.

Claims

1. A method for color measurement on printed materials produced by a printing press, which comprises: measuring with at least one first color measuring device installed in the printing press, and outputting a signal from the first color measuring device when measured color values registered on the printed materials are located within a predefined tolerance range for a predefined period; andafter the signal has been output from the first color measuring device, performing a color measurement on one of the printed materials with at least one second color measuring device.

2. The method according to claim 1, wherein the second color measuring device is located outside the printing press.

3. The method according to claim 1, wherein the first color measuring device and the second color measuring device are connected to each other via a communications link.

4. The method according to claim 1, wherein the predefined period corresponds to a predefined time interval.

5. The method according to claim 1, wherein the predefined period corresponds to a predefined number of printed materials produced.

6. The method according to claim 1, wherein at least one of the first color measuring device and the second color measuring device communicates with a control computer of the printing press.

7. The method according to claim 1, which comprises: deriving measured color values from the color measurement on the printed material with the second color measuring device, and performing a desired value—actual value comparison between the measured color values with a print original; andbased on a determined deviation of the measured color values, performing color control operations in inking units of the printing press.

8. The method according to claim 1, which comprises measuring the printed materials with the first color measuring device during continuous printing operation and defining a tolerance limit for the measured colored values determined in the process, and, if the tolerance limit is exceeded, outputting a warning signal via an operating device.

9. The method according to claim 8, which comprises measuring the printed materials during continuous printing operation by way of the first color measuring device, calculating a trend of color deviations in a computer and, in the event of a calculated trend which, if extrapolated, would lead to a violation of predefined tolerance limits, outputting a warning signal via an operating device.

10. An apparatus for carrying out the method according to claim 1, wherein the first color measuring device is provided for the purpose of recording the variation in the color within the predefined period.

11. The apparatus according to claim 10, wherein the second color measuring device is a spectrophotometer.

12. The apparatus according to claim 10, wherein the first color measuring device is an RGB sensor.

13. The apparatus according to claim 10, wherein the first color measuring device has one or more spectral measuring heads.

14. A printing press, comprising an apparatus for performing the method according to claim 1.

15. An apparatus for color measurement on printed materials produced by a printing press, comprising: at least one first color measuring device installed in the printing press for measuring color values on the printed materials, said first color measuring device being configured to output a signal indicating that measured color values registered on the printed materials lie within a predefined tolerance range for a predefined period; andat least one second color measuring device configured to perform a color measurement on one of the printed materials after the signal has been output from said first color measuring device.

16. The apparatus according to claim 15, wherein said second color measuring device is a spectrophotometer.

17. The apparatus according to claim 15, wherein said first color measuring device is an RGB sensor.

18. The apparatus according to claim 15, wherein said first color measuring device has one or more spectral measuring heads.

19. A printing press, comprising an apparatus according to claim 15.