Method for compensating for defective printing nozzles in an inkjet printing machine
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.
1. A method of compensating for defective printing nozzles in an inkjet printing machine by way of a computer, the method comprising:
to compensate for defective printing nozzles, increasing an ink drop volume of neighboring printing nozzles;
determining real positions of print dots of all printing nozzles;
to compensate for a printing nozzle failure, calculating required ink drop volumes of respective neighboring printing nozzles for each 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, calculating reduced ink drop volumes for respective next but one printing nozzles; and
calculating all ink drop volumes as a function of the print dots of the respective printing nozzles;
calculating the increased and reduced ink drop volumes of the respective next and next but one printing nozzles, respectively, with the computer by initially calculating values of the increased and reduced ink drop volumes on a basis of optimum print dots of the next and next but one printing nozzles, respectively, and subsequently determining dependencies of the increased and reduced ink drop volumes on the real print dots of the next and next but one printing nozzles, respectively, on a basis of calculated values, and subsequently calculating real values of the increased and reduced ink drop volumes by applying the determined dependencies.
2. The method according to claim 1 , which comprises determining the dependencies of the increased and reduced ink drop volumes on the real print dots by taking measurements on inkjet test stands or by simulation.
3. The method according to claim 1 , which comprises calculating with the computer the increased and reduced ink drop volumes of the respective next and next but one printing nozzles additionally or alternatively by determining and applying the dependencies of the increased and reduced ink drop volumes on the amplitude of the respective printing nozzles.
4. The method according to claim 1 , which comprises describing the dependencies of the increased and reduced ink drop volumes on the real print dots of the next and next but one printing nozzles, respectively, in characteristic curves and calculating the dependencies during the application by the computer by interpolation.
5. The method according to claim 1 , which comprises taking into consideration interdependencies between the real print dots of the next and next but one printing nozzles, respectively, for calculating the increased and reduced ink drop volumes of the respective next and next but one printing nozzles, respectively.
6. The method according to claim 1 , which comprises calculating with the computer the increased and reduced ink drop volumes of the respective next and next but one printing nozzles, respectively, also for and based on the print dots and/or the amplitude of the neighboring printing nozzles that are farther away.