Inkjet Print Width Calibration for Uniform Color Density
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Solution Overview
Problem
Inkjet printers face challenges in maintaining consistent color density across the printing width due to variations in ink flow velocity, temperature, or pressure, leading to inconsistent droplet formation and print quality.
Innovation Solution
A method involving printing a 2-dimensional pattern with varying nominal densities, recording color values with a camera, deriving correction curves for each column, and adjusting printing signals to homogenize droplet formation across the print width using a control unit and piezo elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manual inspection and adjustment methods are used (as in US 2009/028585 A1), then print quality can be improved at seams, but the process requires user intervention and is time-consuming
Solution Approach 1:
The system performs self-calibration by automatically printing test patterns, capturing images, analyzing density variations, and generating correction curves without human intervention. The control unit autonomously processes the calibration data and applies corrections to printing signals, enabling the printing system to self-optimize its performance.
Solution Approach 2:
The calibration process is performed in advance before actual production printing. Test patterns are printed and analyzed beforehand to establish correction curves that are stored and applied during normal operation, preventing quality issues before they occur rather than correcting them during production.
2Manufacturing precision
If correction curves are derived for each column individually, then color density consistency across printing width is improved, but computational effort increases
Solution Approach 1:
The printing width is divided into multiple columns, and correction curves are generated independently for each column based on its specific density characteristics. This segmentation allows targeted correction of local variations without requiring complex global models, balancing precision with computational efficiency.
Solution Approach 2:
Each column receives a customized correction curve tailored to its specific density deviations rather than applying a uniform correction across the entire printing width. This local approach optimizes color density consistency for each region while keeping the computational model relatively simple and modular.
3Manufacturing precision
If voltage pulse parameters are adjusted for each nozzle group, then droplet formation homogeneity is improved, but device control complexity increases
Solution Approach 1:
Voltage pulse parameters (amplitude, duration, shape) are individually adjusted for each nozzle group based on its specific performance characteristics. This localized parameter optimization ensures homogeneous droplet formation across all nozzles while maintaining a relatively simple control architecture that only requires storing and applying pre-determined correction parameters for each nozzle group.
Solution Approach 2:
The system optimizes droplet formation by adjusting electrical parameters (voltage pulse characteristics) applied to piezo elements rather than modifying mechanical or thermal parameters. This approach provides precise control over droplet volume, shape, and velocity through electrical parameter modification, achieving homogeneity without complex mechanical adjustments.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Achieves consistent color density by correcting ink ejection variations, ensuring high-quality prints without user intervention and reducing computational effort.
Implementation Method 1
For a piezoelectric inkjet printer, the step of correcting the printing signals can involve adjustment of voltage pulse amplitudes, durations and/or shapes applied at the print head piezo elements
Data Source
Figure 1~2
AI summary
The invention relates to a method for improving the consistency of the color density over the printing width of an inkjet printer (10) comprising the steps of: - Printing a 2-dimensional pattern (32), wherein the 2-dimensional pattern (32) has the same nominal print density over a printing width and varying nominal print densities in printing direction; - Dividing the 2-dimensional pattern (32) in multiple columns (38) across the printing width; - Recording with a camera (24) at least one color value for each nominal print density in each of the columns (38); - Deriving a correction curve for each column (38) from the recorded color values; and - Correcting printing signals and/or printing patterns with the correction curves. Furthermore, the invention relates to an inkjet printer (10).