Inkjet Nozzle Compensation via Automated Test Chart Analysis
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Solution Overview
Problem
Existing methods for compensating defective inkjet printing nozzles often result in visible defects in printed images, especially when using UV inks, due to manual determination of compensation values which can lead to undercompensation or overcompensation issues.
Innovation Solution
An automated method using a test chart with halftone test fields and a digital computer analysis to determine optimal compensation values for printing nozzles, ensuring homogeneity and minimizing defects by selecting the best compensation value based on standard deviation metrics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual determination of compensation values is used, then the process is simple to operate, but the manufacturing precision deteriorates due to undercompensation or overcompensation errors
Solution Approach 1:
The system performs self-diagnosis and self-compensation by automatically analyzing test charts and determining optimal compensation values without manual intervention. The control unit autonomously processes test images, calculates compensation parameters, and adjusts nozzle output to eliminate defects.
Solution Approach 2:
The system implements a feedback loop where test charts are printed, scanned, analyzed, and used to automatically adjust compensation values for defective nozzles. This closed-loop feedback ensures continuous optimization of print quality without manual intervention.
2Manufacturing precision
If automated analysis with multiple test fields is used, then the manufacturing precision improves through precise compensation value determination, but the device complexity increases
Solution Approach 1:
The test chart is segmented into multiple test fields with different patterns (halftones, solid tones, gradients) to systematically test various compensation scenarios. This segmentation allows comprehensive evaluation of compensation effectiveness across different printing conditions.
Solution Approach 2:
The test chart serves multiple functions: it tests compensation effectiveness, identifies defective nozzles, evaluates ink distribution, and provides data for optimization. This multi-functionality reduces the need for separate testing procedures and equipment.
3Manufacturing precision
If compensation values are optimized for each tonal value, then the manufacturing precision improves, but the loss of time increases due to extended testing and analysis
Solution Approach 1:
Compensation values are determined in advance through systematic testing of multiple tonal values before actual production printing. This preliminary characterization allows the system to store and retrieve optimized compensation parameters during normal operation, eliminating the need for real-time testing.
Solution Approach 2:
The system characterizes compensation behavior across different tonal values and ink amounts, creating a parameter map that describes how compensation should vary with printing conditions. This allows automatic selection of appropriate compensation values based on the specific printing task without retesting.
Data Source
AI summary
A method of printing improved printed products using defect-free printing machine nozzles and compensated defective nozzles includes printing products and a test chart with test fields onto a transported substrate, the test fields having tonal values, every test field including an unprinted line from a nonactivated, nonprinting nozzle compensated by a neighboring nozzle having a compensation value, pairs of tonal value and compensation value being specified and used for the chart, recording an image of the chart, computer-analyzing the image and determining the compensation value. Every pair of tonal value and compensation value is used multiple times in the chart and a corresponding number of spaced apart test fields is created. A characteristic value representing test field homogeneity and determining compensation value quality is assigned to every measuring field. The best characteristic value regarding a specified criterion and the compensation value is determined for every tonal value.