Heidelberger Druckmaschinen Ag

Andreas Fehlner

Andreas Henn

Steffen Neeb

Nicklas Raymond Norrick

Thomas Wolf

Jens Forche

Ilias Trachanas

Hans Koehler

Mina Hakim Latif Abosetta

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 assessing the condition and improving the printing quality of printing nozzles in printheads of an inkjet printing machine includes printing a nozzle test chart formed of a specific number of horizontal rows of equidistant vertical lines printed periodically underneath one another, with only every nprinting nozzle contributing to the test chart in every row of the test chart and n corresponding to a different number between one and the specific number of horizontal rows, recording and digitizing the test chart and analyzing the test chart regarding the condition of the contributing nozzles by using a computer. The nozzles printing horizontal lines between the horizontal rows complementing the equidistant vertical lines to form quadrangular objects used by the computer to analyze the condition of the contributing nozzles. Measures are taken to improve the printing quality of the nozzles depending on the condition of the contributing nozzles.

Method for assessing the condition and improving the printing quality of printing nozzles in printheads of an inkjet printing machine and improved printing nozzle test chart

A method for detecting and compensating for defective print heads in an inkjet printing machine uses a computer to analyze printing nozzle test charts and/or area coverage elements to obtain characteristic values of individual printing nozzles in a print head, to calculate the failure probabilities of these printing nozzles on the basis of thresholds, and to compensate for a printing nozzle that exceeds a specified failure probability. The computer uses the individual failure probabilities of the individual printing nozzles in a print head to calculate the failure probability of the print head and initiates compensation measures as a function of the calculation. The thresholds correspond to a multi-dimensional characteristic value threshold based on which the computer calculates the failure probability of a printing nozzle by using an algorithm including kernel density estimation through a multidimensional distribution function.

Method for detecting and compensating for defective print heads in an inkjet printing machine by stochastic print head monitoring

A method detects defective print nozzles in an inkjet printing machine by a computer. In a first phase within the context of a print job, print nozzle test patterns are printed beside a subject on a printing substrate. These print nozzle test patterns are then digitized by an image sensor and sent to the computer, where they are analyzed by the computer to determine the current state of the print nozzles, including defective print nozzles. After the first phase, the print nozzle test patterns are modified by the computer on the basis of the current state of the print nozzles and, in a second phase, the modified print nozzle test patterns are printed, digitized and evaluated by the computer with regard to the determination of the current state of the print nozzles and defective print nozzles.

Method for detecting a defective print nozzle using a variable print nozzle test pattern

A method for detecting and compensating for defective printing nozzles in an ink jet printing machine by using a computer includes printing printing nozzle test charts next to an actual print in a production run, subsequently recording and digitizing the printed printing nozzle test charts by using at least one image sensor, evaluating recorded test charts and, based thereon, defining characteristic values for all printing nozzles contributing to the printed printing nozzle test charts by using the computer, calculating a failure probability for every contributing printing nozzle based on the determined characteristic values by applying a statistical prediction model using the computer, and switching off and compensating for all printing nozzles exceeding a first defined threshold for the calculated failure probability. A printing operation is then carried out on the ink jet printing machine with printing nozzle compensation.

Method for detecting and compensating for defective printing nozzles in an ink jet printing machine

A method for detecting and compensating defective printing nozzles in an inkjet printing machine includes periodically printing at least one printing nozzle test chart having horizontal rows of equidistant vertical lines underneath one another, with only nozzles contributing to the test chart in every row corresponding to horizontal rows, and printing an area coverage element geometrically associated with the test chart. Both elements are recorded by an image sensor and evaluated by a computer. The computer identifies print defects by evaluating the area coverage element and allocates the defects to defective nozzles. The computer evaluates the test chart based on thresholds to detect defective nozzles and compensate detected defective nozzles. The computer compares the detected defective nozzles from the area coverage element and the test chart to identify detected defective nozzles causing defects in only one element and calculates the thresholds based thereon to minimize the detected defective nozzles.

Method for detecting and compensating for defective printing nozzles in an inkjet printing machine using a threshold calculation based on weighting factors

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Mannheim, Germany

Andreas Fehlner