Heidelberger Druckmaschinen Ag

Johannes Muehl

Hans Koehler

Martin Mayer

Andreas Henn

Steffen Neeb

Nicklas Raymond Norrick

Frank Muth

Jan Krieger

Roland Stenzel

Mina Abosetta

A method detects defective printing nozzles in an inkjet printing machine having a computer. The method includes printing a multi-row nozzle test chart for detection purposes, the test chart contains a number of horizontal rows of equidistant vertical lines printed periodically and disposed underneath one another. Wherein in every row of the nozzle test chart periodically only those respective printing nozzles of the print head contribute to the first element of the nozzle test chart that correspond to the specified number of the horizontal rows. An area coverage element geometrically associated with the nozzle test chart is printed. Both elements are recorded by an image sensor and both elements are evaluated by the computer. Defective printing nozzles are identified by evaluating the recorded nozzle test chart by the computer. Defects are allocated in the area coverage element to the printing nozzles in the nozzle test chart by the computer.

Determination of thresholds to detect missing printing nozzles

A method for detecting defective printing nozzles in an inkjet printing machine includes printing a multi-row printing nozzle test chart formed of horizontal rows of equidistant vertical lines periodically underneath one another, with only printing nozzles in a print head contributing to every row of the test chart corresponding to the horizontal rows. An area coverage element geometrically associated with the test chart is printed, both elements are recorded by an image sensor and analyzed by the computer. The computer analyzes the recorded area coverage element to detect print defects and allocates defects to a region of geometrically close printing nozzles. An analysis of the test chart in the region identifies nozzles causing the defect. Defective printing nozzles are detected based on thresholds, the detected printing nozzles are then compensated, and in the analysis of the recorded area coverage element, influences of the sensor are eliminated by shading correction.

Method for detecting defective printing nozzles in an inkjet printing machine

Growing community of inventors

Heidelberg, Germany

Johannes Muehl