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

Patent metadata

Field	Value
Publication number	US-10625499-B2
Application number	US-201916508358-A
Country	US
Kind code	B2
Filing date	Jul 11, 2019
Priority date	Jul 11, 2018
Publication date	Apr 21, 2020
Grant date	Apr 21, 2020

Abstract

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.

First claim

The invention claimed is:

1. A method for detecting and compensating for defective print heads in an inkjet printing machine; the method comprising the following steps:
using a computer to analyze at least one of printing nozzle test charts or area coverage elements to obtain characteristic values for individual printing nozzles in a print head;
using the computer to calculate failure probabilities of the printing nozzles on a basis of thresholds;
using the computer to compensate for a printing nozzle exceeding a specified failure probability;
using the computer to calculate the failure probability of a printing nozzle by using an algorithm including kernel density estimation through a dimensional distribution function based on the thresholds corresponding to a multi-dimensional characteristic value threshold; and
initializing compensation measures, using the computer, as a function of a failure probability of the print head calculated by utilizing the individual failure probabilities of the individual printing nozzles in the print head.

2. The method according to claim 1 , which further comprises forming the characteristic values of the individual printing nozzles from a series of individual measurements and using the computer to statistically describe the characteristic values.

3. The method according to claim 1 , which further comprises using the computer to calculate the failure probability of the print head by multiplying with one another non-failure probabilities of n adjacent printing nozzles of a printing nozzle identified as defective in the print head as a result of the analysis of at least one of the printing nozzle test charts or the area coverage elements, to obtain a compensation probability for every defective printing nozzle, and then using the computer to calculate the failure probability of the print head based on the compensation probabilities.

4. The method according to claim 3 , which further comprises based on the compensation probabilities for every printing nozzle identified as defective, using the computer to calculate the failure probability of the print head by multiplying the compensation probabilities with one another.

5. The method according to claim 4 , which further comprises calculating the failure probability of the print head by multiplying with one another only the non-failure probabilities of those n neighboring printing nozzles that have not already been declared defective and switched off.

6. The method according to claim 4 , which further comprises initiating compensation measures by using the computer to take into consideration, in addition to the failure probability of the print head, whether one of the respective n adjacent printing nozzles of a printing nozzle that has been declared defective and been switched off has likewise been declared defective and been switched off.

7. The method according to claim 3 , which further comprises using the computer to calculate the failure probability of the print head by selecting a lowest value among the compensation probabilities for every defective printing nozzle.

8. The method according to claim 1 , which further comprises selecting the measures for compensation as purging, washing or replacing the print head, and initiating the measures for compensation when the failure probability of the print head exceeds a specified threshold.

9. The method according to claim 1 , which further comprises using the computer to calculate the individual failure probabilities of the individual printing nozzles in a print head by taking a position of the printing nozzles in the print head into consideration.

10. The method according to claim 1 , which further comprises weighting a printing behavior of every single printing nozzle by applying a loss function to a characteristic value progression, when calculating the individual failure probabilities of the individual printing nozzles in a print head.

Assignees

• Heidelberger Druckmasch Ag

Inventors

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

Classifications

• B41J2/16526 Primary

  by applying pressure only · CPC title

• B41J2/135 Primary

  Nozzles · CPC title

• B41J2/165

  Prevention {or detection} of nozzle clogging, e.g. cleaning, capping or moistening for nozzles · 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