Zone-Specific Ink Metering for Offset Press Color Control
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Solution Overview
Problem
Offset printing units face challenges in accurately supplying ink due to uneven ink requirements across zones, leading to underinking or overinking in areas with different area coverages, and the increased dampening solution affects color density.
Innovation Solution
The method involves independently adjustable ink metering elements in zones transverse to the printing direction, with presetting values determined to minimize ink deviation by accounting for humidity and area coverage, using correction values to adjust ink metering elements based on the relationship between dampening solution and density deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of dampening solution is determined by the zone with the greatest ink requirement, then the maximum dampening solution requirement is met, but low area coverage areas become underinked due to oversupply of dampening solution
Solution Approach 1:
The patent divides the dampening solution supply into zone-specific portions, where each ink metering element receives dampening solution according to its specific ink requirements. This segmentation allows each zone to receive the appropriate amount of dampening solution rather than being governed by the maximum requirement of any single zone, thereby preventing underinking in low area coverage areas while still meeting the needs of high area coverage zones.
Solution Approach 2:
The patent applies local quality by adjusting the dampening solution supply according to the specific characteristics of each zone. The control device calculates and supplies dampening solution in amounts tailored to the ink requirements of individual ink metering elements, ensuring that each zone receives the appropriate level of dampening solution rather than a uniform supply based on maximum requirements.
2Ease of operation
If ink metering elements are preset based on area coverage using characteristic curves, then the presetting is simplified, but other process variables influencing ink requirement are not considered
Solution Approach 1:
The patent implements feedback by using the control device to calculate and adjust presetting values based on multiple process variables including area coverage, printing medium properties, and printing machine characteristics. The control device receives information about these variables and dynamically adjusts the presetting of ink metering elements to achieve accurate ink supply, moving beyond simple characteristic curve-based presetting.
Solution Approach 2:
The patent applies preliminary action by calculating and determining presetting values for ink metering elements before the actual printing process begins. The control device uses available information about the printing job, printing medium, and machine characteristics to pre-calculate optimal presetting values, allowing for accurate ink supply from the start without requiring trial and error adjustments during printing.
3Adaptability or versatility
If characteristic curves are learned from actual settings for dynamic updating, then the presetting adapts to specific conditions, but the influence of dampening solution on color density is not compensated
Solution Approach 1:
The patent enhances feedback by incorporating the relationship between dampening solution amount and color density into the learning process. The control device not only learns from actual ink metering element settings but also compensates for the influence of dampening solution on color density. This allows the system to adapt to specific printing conditions while maintaining accurate color density control.
Solution Approach 2:
The patent addresses asymmetry by recognizing that the relationship between dampening solution and color density is not uniform across different zones and printing conditions. The control device applies asymmetric compensation, adjusting presetting values based on the specific dampening solution conditions in each zone and the corresponding impact on color density, rather than applying a uniform correction factor.
Data Source
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AI summary
The method involves applying printing ink on an ink roller of an inking unit using a set of color dosing elements, which are adjusted independent from one another. The dosing elements are arranged transverse to a printing direction in zones. Each color dosing element is preset depending on a color requirement in the zone that is assigned to the color dosing elements. A value of the preset for the color dosing elements is determined such that a deviation of the coloring from an expected value in the zone is reduced, where the deviation is caused by large quantity of dampening agent. An independent claim is also included for a printing machine with a control computer and an offset printing unit.