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

Patent metadata

Field	Value
Publication number	US-10596806-B2
Application number	US-201816161141-A
Country	US
Kind code	B2
Filing date	Oct 16, 2018
Priority date	Nov 24, 2017
Publication date	Mar 24, 2020
Grant date	Mar 24, 2020

Abstract

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.

First claim

The invention claimed is:

1. A method for detecting and compensating for failed printing nozzles in an ink jet printing machine by using a computer, the method comprising the following steps:
carrying out printing of printing nozzle test charts next to an actual print during a production run and subsequently recording and digitizing the printed printing nozzle test charts by using at least one image sensor;
evaluating the recorded test charts and, based thereon, determining characteristic values for all printing nozzles contributing to the printing of the printing nozzle test chart 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 by using the computer;
for the application of the prediction model, establishing the characteristic values for every printing nozzle multiple times, with every evaluation of the printed printing nozzle test chart corresponding to one pass, and saving and using the characteristic values having been established multiple times to calculate the failure probability;
switching off all printing nozzles exceeding a first defined threshold for the calculated failure probability and compensating for the switched-off nozzles; and
carrying out a printing operation on the ink jet printing machine with printing nozzle compensation.

2. The method according to claim 1 , which further comprises printing the printing nozzle test chart by forming a specified number of horizontal rows of equidistant vertical lines printed periodically and disposed underneath one another, and providing every row of the nozzle test chart with only those printing nozzles of the print head of the ink jet printing machine corresponding to the specified number of the horizontal rows periodically contributing to a first element of the printing nozzle test chart.

3. The method according to claim 2 , which further comprises including thickness, slope and color value of the vertically printed equidistant lines as well as a utilized capacity of the contributing printing nozzles in the characteristic values.

4. The method according to claim 1 , which further comprises using the failure probability of every one of the printing nozzles to represent a probability that a printing nozzle will exceed a tolerance limit for print quality resulting from the characteristic values.

5. The method according to claim 1 , which further comprises using the characteristic values having been established multiple times as a function of a process variation of the characteristic values over a progression of individual passes, and for the same failure probability, allowing the characteristic values of progressions of lower process variation of the characteristic values to get closer to a tolerance limit than progressions of greater process variation.

6. The method according to claim 5 , which further comprises converting the characteristic values having been established multiple times into statistical process factors forming an expectation value and a confidence interval, determining the statistical process factors by linear or non-linear regression of the characteristic values having been established multiple times, and using a regression model of any desired order for the linear or non-linear regression.

7. The method according to claim 6 , which further comprises creating the statistical process factors with a time-based weighting of the characteristic values having been established multiple times, and carrying out the time-based weighting by causing newer characteristic values to have a linearly or exponentially higher weight than older characteristic values.

8. The method according to claim 1 , which further comprises calculating the failure probability for all printing nozzles contributing to the printing of the printing nozzle test charts by assuming and using multimodal distributions of the characteristic values in addition to a unimodal distribution of the characteristic values.

9. A method for detecting and compensating for failed printing nozzles in an ink jet printing machine by using a computer, the method comprising the following steps:
carrying out printing of printing nozzle test charts next to an actual print during a production run and subsequently recording and digitizing the printed printing nozzle test charts by using at least one image sensor;
evaluating the recorded test charts and, based thereon, determining characteristic values for all printing nozzles contributing to the printing of the printing nozzle test chart 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 by using the computer;
switching off all printing nozzles exceeding a first defined threshold for the calculated failure probability and compensating for the switched-off nozzles;
allowing printing nozzles having been switched off for the printing of the actual print to still contribute to the printing of the printing nozzle test charts;
continuing to calculate a failure probability for the switched off printing nozzles;
again using the switched off printing nozzles for printing the actual print in the production run if the calculated failure probability stays below a second defined threshold; and
carrying out a printing operation on the ink jet printing machine with printing nozzle compensation.

Assignees

• Heidelberger Druckmasch Ag

Inventors

• Neeb Steffen
• Norrick Nicklas Raymond
• Henn Andreas
• Fehlner Andreas
• Wolf Thomas
• Forche Jens

Classifications

• B41J2/0451 Primary

  for detecting failure, e.g. clogging, malfunctioning actuator · CPC title

• B41J2/2146

  for line print heads · CPC title

• B41J2/2139

  Compensation for malfunctioning nozzles creating dot place or dot size errors (generating single droplets or particles on demand by pressure, e.g. electromechanical transducers B41J2/045) · CPC title

• B41J2/04586

  controlling heads of a type not covered by groups B41J2/04575 - B41J2/04585, or of an undefined type · CPC title

• B41J2/2142

  Detection of malfunctioning nozzles (generating single droplets or particles on demand by pressure, e.g. electromechanical transducers B41J2/045, B41J2/05; jet deflection sensors B41J2/125; for cleaning purposes B41J2/16579) · CPC title