Vacuum Pulldown for Print Medium Wrinkle Control
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Solution Overview
Problem
In digitally controlled printing systems, the expansion and contraction of print media due to moisture content lead to dimensional changes, causing image quality issues such as wrinkles and flutes, which result in print defects and ink smearing.
Innovation Solution
A method involving a vacuum assembly with a vacuum manifold aligned with transport rollers to increase the wrap angle of the print medium around the rollers, preventing fluttering and smearing, and reducing the formation of wrinkles by maintaining better contact with the rollers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the print medium is supported by rollers during printing, then the print medium is prevented from moving freely, but the moisture-induced expansion causes localized buckling and wrinkle formation
Solution Approach 1:
The support system is segmented into multiple independent vacuum assemblies positioned at different locations along the print medium width. Each vacuum assembly independently applies vacuum force to specific zones, allowing localized control of print medium contact with rollers. This segmentation enables the system to maintain stability in supported areas while allowing controlled movement in non-supported areas, preventing wrinkle formation.
Solution Approach 2:
The vacuum assemblies are made dynamically controllable through independent activation and adjustment of each assembly. The system can dynamically adjust which vacuum assemblies are active and at what vacuum levels, adapting to real-time printing conditions. This dynamic control allows the system to optimize the balance between preventing print medium movement and avoiding wrinkle formation during the printing process.
2Adaptability or versatility
If the print medium is allowed to expand freely due to moisture absorption, then dimensional changes occur, but restricting expansion through roller contact causes flutes and wrinkles
Solution Approach 1:
Different regions of the print medium are subjected to different vacuum forces by individual vacuum assemblies. Areas with higher moisture content or greater expansion tendency receive adjusted vacuum levels compared to drier areas. This local quality approach allows the system to accommodate dimensional changes in specific regions while maintaining overall print quality, preventing flutes and wrinkles by allowing controlled local expansion.
Solution Approach 2:
The vacuum force parameter is continuously adjustable for each vacuum assembly independently. The system can change vacuum levels in response to moisture content variations, print speed changes, or medium type variations. This parameter flexibility enables the system to adapt to dimensional changes caused by moisture absorption while maintaining print quality through dynamic adjustment of the vacuum force applied to different zones.
3Manufacturing precision
If multiple vacuum assemblies are used to control print medium contact, then wrinkle formation is reduced, but system complexity increases
Solution Approach 1:
Each vacuum assembly is designed as a universal module that can be applied to different positions and configurations along the print medium. The modular design allows the same basic vacuum assembly structure to serve multiple functions at different locations. This universality reduces overall system complexity by using standardized components rather than custom-designed elements for each position, while still providing the needed distributed control to prevent wrinkles.
4Stability of the object's composition
If the wrap angle of print medium around rollers is increased, then contact and stability are improved, but moisture-related dimensional changes are exacerbated
Solution Approach 1:
The vacuum assemblies apply partial vacuum force to specific zones rather than attempting to secure the entire print medium surface. By applying vacuum only where needed to prevent fluttering and maintain stability, the system avoids excessive contact that would exacerbate moisture-induced dimensional changes. This partial action approach provides just enough stabilization without over-constraining the print medium.
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
This solution effectively prevents print medium fluttering, reduces wrinkle formation, and enhances image quality by maintaining consistent contact and reducing moisture-related dimensional changes.
Implementation Method 1
applying a vacuum force proximate to the second side of the print medium such that at least a portion of the moving print medium is deflected thereby increasing a wrap angle of the moving print medium around the aligned transport roller
Data Source
AI summary
A method for printing on a moving print medium in a printing system is disclosed. The method includes providing a linehead defining one or more print zones. A plurality of transport rollers are provided, wherein at least one transport roller is disposed opposite the linehead, adjacent to the second side of the print medium, and aligned with one of the print zones. A vacuum assembly is disposed opposite the second side of the print medium and includes a vacuum manifold aligned with the aligned transport roller. The print medium is moved through the printing system and a vacuum force operates on the print medium such that at least a portion of the print medium is deflected thereby increasing a wrap angle of the moving print medium around the aligned transport roller. Liquid is jetted from the linehead onto the print medium to form a print.