Determination of thresholds to detect missing printing nozzles

US10647110B2 · kind B2 · utility

Assignee

• Heidelberger Druckmaschinen AG · DE

Inventors

• Johannes Muehl · Ennepetal, DE
• Hans Koehler · Graz, AT

Key dates

• Filing date: Oct 10, 2018
• Grant date: May 12, 2020
• Expiry date: Oct 10, 2038

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B41J2/2146
• WIPO field: Textile and paper machines
• WIPO sector: Mechanical engineering

Abstract

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.