Method for computer-aided detection of faulty printing nozzles in an inkjet printing machine

Abstract

The invention relates to a method for detecting faulty printing nozzles in an inkjet printing machine by means of a computer, printing a multi-line nozzle test pattern, including a defined number of horizontal lines, and printing an area coverage geometrically assigned to the nozzle test pattern elements, both of which are detected by at least one image sensor and analyzed by a computer, by analyzing the detected nozzle test pattern to identify faulty printing nozzles, assigning defects in the surface covering elements to printing nozzles in the nozzle test pattern, defining value range, based on which threshold values ​​are derived for detecting faulty printing nozzles, the defects found in the surface covering elements are assigned according to the deviations in the nozzle test patterns at corresponding locations transverse to the printing direction, always The detected defects are assigned in the nozzle test pattern to those print nozzles which, taking into account the parameters to be evaluated, caused the defects with the highest probability.

Description

technical field [0001] The invention relates to a threshold value determination for a method for detecting faulty printing nozzles. Background technique [0002] The invention is in the technical field of digital printing. [0003] In digital printing (in this case inkjet printing) failures of individual printing nozzles of the printing heads of inkjet printers often occur. These failures include a variety of possible failure types. This may be due to printing with a reduced drop volume, or to a deviation of the printing dots of this printing nozzle (which causes skewed printing), or even to a complete failure of this printing nozzle. The cause of these faults can be, for example, the penetration of foreign matter (in particular dust) into the print nozzles or the drying of the ink in the print nozzles of the print head. All these fault types of faulty nozzles are also generally referred to as "missing nozzles" according to the English term missing nozzle. These "missing...

AI Technical Summary

Problems solved by technology

Furthermore, the print image data to be generated within the scope of the printing job are often not suitable for an exact function check of the individual printing nozzles

Another problem is the assignment of detected image defects in the printed image to specific printing nozzles

However, here, as with detection based on the original printed image, there is always the general problem that the individual printing nozzles causing the defect cannot be identified within the surface covering element

However, this prior art does not disclose printed surface covering elements, but the determination of the threshold is realized purely based on the detection and analysis of the printed nozzle test pattern

Furthermore, this solution has the disadvantage that the threshold value for evaluating the deviation of the printing nozzles is carried out independently of the actual printing result.

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