Inkjet Nozzle Failure Detection at Print Head Edges
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Solution Overview
Problem
Existing methods for detecting failed printing nozzles at the edge of an inkjet printing machine are inaccurate due to the limitations of digital camera resolution, which prevents precise identification of nozzle failures using standard test patterns without locator marks, leading to impractical single-row test patterns and incomplete compensation.
Innovation Solution
A method that evaluates the digital image of a nozzle test pattern by measuring the distance between the beginning of each row, allowing detection of failed nozzles by identifying shifts in row starts, even at the edge of the print head, without the need for locator marks, using the resolution to accurately determine nozzle failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard test patterns with locator marks are used to detect failed nozzles, then detection accuracy is improved, but device complexity and manufacturing cost increase due to additional marks and processing requirements
Solution Approach 1:
The patent extracts and removes the locator marks from the test pattern structure, retaining only the essential test elements (vertical line pairs) needed for nozzle detection. This simplifies the test pattern while maintaining detection capability through the modified evaluation method that uses horizontal positioning of line pairs instead of locator marks for reference.
Solution Approach 2:
The test pattern is segmented into multiple independent rows, each containing vertical line pairs printed by specific nozzles. This segmentation allows the evaluation to focus on local line pair positioning within each row, enabling accurate detection without requiring complex global reference marks.
2Device complexity
If single-row test patterns are used to simplify the test structure, then device complexity is reduced, but measurement precision deteriorates because camera resolution cannot accurately distinguish adjacent nozzles
Solution Approach 1:
The patent transitions from relying solely on vertical resolution (single row) to utilizing horizontal positioning information across multiple rows. By arranging line pairs in multiple rows and evaluating their horizontal positions, the system achieves accurate nozzle detection even when vertical resolution is insufficient to distinguish adjacent nozzles.
3Measurement precision
If digital camera resolution is increased to improve detection accuracy, then measurement precision is improved, but device cost and complexity increase
Solution Approach 1:
The patent changes the evaluation parameters from requiring high vertical resolution to utilizing horizontal position information. By measuring the horizontal distance between line pairs in consecutive rows and comparing it to expected values, the system achieves accurate detection with standard camera resolution, avoiding the need for high-resolution cameras.
4Reliability
If locator marks are added to the test pattern, then detection reliability is improved, but manufacturing precision requirements worsen due to additional alignment and positioning constraints
Solution Approach 1:
The test pattern elements (vertical line pairs) serve dual purposes: they are both the test objects and the reference elements for detection. The line pairs themselves provide the positional information needed for evaluation, eliminating the need for separate locator marks and reducing alignment requirements.
Data Source
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AI summary
A method for detecting failed print nozzles (11) in an inkjet printing machine (7) by a computer (6), wherein a nozzle test pattern (14) is printed for each color separation, which consists of a specific number of horizontal rows of periodically vertically printed, equally spaced lines (15) arranged one below the other, wherein in each row of the nozzle test pattern (14) only those print nozzles corresponding to the specific number of horizontal rows contribute periodically to the nozzle test pattern (14), and wherein the printed nozzle test pattern (16) is captured for evaluation by means of an image sensor, digitized and transmitted to the computer (6) for evaluation, and which is characterized in that, in order to determine failed print nozzles (11) at an edge of the printhead (8, 9), the beginning of the horizontal rows (8, 9) of the nozzle test pattern (16) is examined by the computer (6) during the evaluation of the nozzle test pattern (16).how far the lines (15) at the beginning of the respective row of the nozzle test pattern (16) below deviate geometrically, wherein the computer (6) examines the geometric deviation of the lines (15) insofar as the horizontal distance of the first line (15) of a row of the nozzle test pattern (16) from the first line (15) of the row of the nozzle test pattern (16) below is.