Variable Print Control Bars for Inkjet Nozzle Detection
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Solution Overview
Problem
Inkjet printing machines face challenges in accurately detecting defective nozzles due to irregularities in print substrate transport, leading to non-linear distortions in the recorded image, which result in false positive errors during automated inspection.
Innovation Solution
A method involving multi-line nozzle test patterns with periodically printed, equidistant lines, where the order of horizontal lines is varied from sheet to sheet, ensuring that nozzles closer to the trailing edge are less distorted, allowing for reliable detection of defective nozzles by shifting the position of lines further away from the edge on subsequent sheets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-line nozzle test patterns are printed with fixed line order, then detection of defective nozzles can be performed, but distortion towards the trailing edge causes false positive errors and reduces measurement precision
Solution Approach 1:
The patent applies dynamics by varying the order of horizontal lines in the nozzle test pattern from sheet to sheet. Instead of a fixed line order, the system dynamically changes which line is positioned where in the test pattern, ensuring that no single line position is consistently affected by trailing edge distortion. This dynamic repositioning allows the system to maintain measurement precision despite the presence of distortion.
Solution Approach 2:
The patent implements periodic action by systematically rotating through different line orderings across multiple sheets. Each line in the test pattern periodically occupies different positions relative to the trailing edge over time, allowing the system to average out distortion effects. This periodic repositioning ensures that all nozzles are regularly checked while minimizing the impact of consistent distortion at any single position.
2Productivity
If nozzle test patterns are printed continuously on all sheets, then regular monitoring of print nozzle status is achieved, but distortion at trailing edge positions makes reliable evaluation impossible
Solution Approach 1:
The system maintains continuous nozzle monitoring while dynamically varying line positions to avoid consistent distortion. By periodically changing which line occupies which position in the test pattern, the system ensures that monitoring continues at full productivity while the measurement precision is preserved through the dynamic repositioning that prevents any single line from being consistently degraded by trailing edge effects.
3Productivity
If lines in nozzle test pattern are positioned close to trailing edge to maximize usage of printing substrate, then more nozzles can be tested, but distortion increases making detection unreliable
Solution Approach 1:
The patent resolves this contradiction by dynamically repositioning lines so that while they remain close to the trailing edge to maximize substrate usage, their relative positions change from sheet to sheet. This ensures that all nozzles can be tested (high productivity) while the dynamic variation prevents any single nozzle's test line from being consistently degraded by distortion (maintained measurement precision).
Solution Approach 2:
The systematic rotation of line orderings allows the system to maintain high nozzle test coverage by keeping lines close to the trailing edge, while the periodic repositioning ensures that distortion affects different lines at different times, allowing reliable detection through averaging and comparison across multiple sheets.
Data Source
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AI summary
A method for detecting defective print nozzles in an inkjet printing machine (4) with a computer (3, 6), wherein multi-line nozzle test patterns (13, 15, 16) are printed onto the printing substrate in the form of printing sheets (8) for detection purposes, the printing sheets consisting of a specific number of horizontal lines (12) of periodically vertically printed, equally spaced lines (14) arranged one below the other in the printing direction, wherein in each line (12) of a nozzle test pattern (13) only the print nozzles of the printhead of the inkjet printing machine (7) that correspond to the specific number of horizontal lines (12) periodically contribute to the first element of the nozzle test pattern (13, 15, 16), the nozzle test patterns (13, 15, 16) are detected by at least one image sensor (5) and evaluated by the computer (3, 6) to determine the defective print nozzles, which is characterized in that the horizontal lines (12) are periodically vertically printed,The order of the equally spaced lines (14) can be varied from printing sheet (8) to printing sheet (8).