Heidelberger Druckmaschinen Ag

Ilias Trachanas

Martin Mayer

Axel Hauck

Andreas Fehlner

Gerd Junghans

Peter Hachmann

Mina Hakim Latif Abosetta

Andreas Schoemann

Thomas Schrank

A method for detecting and compensating for defective printing nozzles in an inkjet printing machine includes printing test sheets each including at least one printing nozzle test chart and at least one gray area for every color separation. The test sheets are recorded and digitized with subsequent pixel-nozzle mapping and amplitude/phase value determination by using a computer. Current measurements are taken at the printing nozzles in between test sheets and customer sheets while being printed. The computer is used for teaching in a SVM model with the results of the current measurement and pixel-nozzle mapping and amplitude/phase determination. The taught-in SVM model and the current measurements are applied to printed, recorded and digitized customer's images to detect defective printing nozzles during production printing on the inkjet printing machine and the detected defective printing nozzles are compensated for.

Method for detecting and compensating for defective printing nozzles in an inkjet printing machine for reducing unusable prints

A method for inspecting images on print products in a printing material processing machine includes recording and digitizing produced print products using at least one image sensor in an image inspection process of a print job using an image inspection system. The recorded digital prints that have been created are compared to a digital reference image by using a computer and, if deviations are found between the recorded digital prints and the digital reference image, print products found to be defective are removed. The image sensor records the produced print products from at least two different viewing angles and/or viewing distances and the computer evaluates the at least two recorded digital prints as a function of the at least two viewing angles and/or viewing distances and assesses them in terms of deviations. A device for inspecting images on print products is also provided.

Method and device for inspecting images on print products using an image inspection robot

A method for compensating for defective printing nozzles in an inkjet printing machine by way of a computer. Defective printing nozzles are compensated for by an increased ink drop volume of neighboring printing nozzles and the real positions of the print dots of all printing nozzles are determined and, to compensate for a printing nozzle failure, the required ink drop volumes of the respective neighboring printing nozzles are calculated for every printing nozzle as a function of the real positions of the print dots of the respective neighboring printing nozzles. In addition to increased ink drop volumes of the respective neighboring printing nozzles, reduced ink drop volumes are calculated for the respective next but one printing nozzles and all ink drop volumes are calculated based on the print dots of the respective printing nozzles.

Method for compensating for defective printing nozzles in an inkjet printing machine

A method for modifying color density values in a dot-based printing system uses a control unit. The control unit implements the modification of the color density values after a raster image has been created and modifies the number and/or size of print dots to be applied to a printing substrate in order to attain pre-defined color density target values.

Method for density compensation by drop size adaptation

A method corrects color density unevenness during a printing operation on an inkjet printing machine having printing nozzles and a computer. The computer modifies the number or size of the drops to be applied to a printing substrate to attain nominal color density values after the processing of a rasterized print image. For different actual tone values, it is determined which target tone value is required to attain a nominal coloration by measuring a test image for every printing nozzle using a color measurement device, and, based thereon, an area coverage-dependent compensation profile is determined and saved on the computer to be applied in the printing operation to calculate the number and size of the drops on the computer.

Multilevel density compensation for digital printing machines

A method corrects for defective printing nozzles in an ink jet printing machine via a computer. The defective printing nozzles are compensated for after the screening process by neighboring printing nozzles applying an increased amount of ink. The method includes precalculating different compensation halftones for different area coverages by the computer, printing the compensation halftones embedded in area coverage halftone areas, evaluating the printed compensation halftones via the computer, and selecting and saving, for every area coverage level, the compensation halftone that best matches the coloration of the original halftone in the respective area coverage halftone area. A defective printing nozzle is detected during production printing by the computer. The local area coverage is determined along the detected defective printing nozzle by the computer. The compensation halftone that has been saved for the determined local area coverage is used to compensate for the defective printing nozzles via the computer.

Compensation method for failed printing nozzles

A method for detecting and compensating for defective printing nozzles in an inkjet printing machine by using a computer, includes shrinking the height of a digitally available image to the image height of a print control strip by using the computer while the image width remains uninfluenced, printing the shrunk digital image onto a printing substrate, recording the printed shrunk digital image by using at least one image sensor, comparing the recorded image with the shrunk digital image by using the computer, detecting defective printing nozzles for the digital image by using the computer based on the comparison and compensating for the detected defective printing nozzles. The digital image is printed onto the following printing substrate by using defective printing nozzle compensation.

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Plankstadt, Germany

Ilias Trachanas