Vacuum Transport Roller Wrap Angle for Print Medium Stability
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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 smearing, as the print medium cannot slip freely on rollers, resulting in flutes or creases that affect print quality.
Innovation Solution
A method involving vacuum transport rollers with a porous sleeve and a vacuum manifold is used to increase the wrap angle of the print medium around the rollers, preventing fluttering and smearing by applying a vacuum force to the second side of the print medium, thereby reducing the formation of flutes and wrinkles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the print medium is supported by rollers during printing, then the print medium is physically moved through the printing system, but the print medium cannot slip freely on the rollers causing flutes or wrinkles due to expansion in crosstrack direction
Solution Approach 1:
The support structure is divided into multiple discrete support members (rollers) spaced along the print medium path. Each roller provides localized support and allows controlled interaction with the print medium, preventing excessive flutter while maintaining transport capability. The segmentation of support into discrete zones allows the print medium to expand slightly between rollers without creating continuous flutes.
Solution Approach 2:
The system uses compliant or elastically deformable support members that can dynamically adapt to the print medium's expansion and contraction. The rollers are designed with compliance characteristics that allow them to yield slightly under the print medium's dimensional changes, preventing rigid constraint that would cause wrinkles, while still providing sufficient support to prevent excessive flutter.
2Manufacturing precision
If the print medium is constrained to prevent fluttering, then image quality is maintained, but the print medium cannot expand freely causing localized buckling and creases
Solution Approach 1:
Different regions of the support structure provide different levels of constraint. The support members are positioned and designed to provide varying degrees of stiffness and compliance along the print medium path. Areas where print medium expansion is expected have more compliant support, while areas requiring stable positioning have stricter constraint, allowing localized adaptation to dimensional changes without creating widespread defects.
Solution Approach 2:
The support system parameters (stiffness, spacing, contact pressure) are optimized to match the print medium's expansion characteristics. By adjusting these parameters, the system transitions from rigid constraint that causes wrinkles to compliant support that accommodates dimensional changes, maintaining image quality while allowing natural expansion and contraction of the print medium.
3Productivity
If multiple printheads are aligned in rows parallel to crosstrack direction, then printing efficiency is improved, but the support structure bottom face becomes wet causing smearing when print medium contacts it
Solution Approach 1:
The harmful wet surface from the support structure is extracted or removed from the printing zone. The support members are designed to remain dry through proper positioning, material selection, or protective coatings, eliminating the source of smearing while maintaining their structural support function for the print medium during high-efficiency multi-printhead operation.
Solution Approach 2:
An intermediary protective layer or coating is applied to the support structure surface that prevents moisture transfer to the print medium. This intermediary layer allows the support structure to remain in its optimal position for efficient printing while blocking the harmful moisture pathway that would cause ink smearing.
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 the formation of flutes and wrinkles, maintaining image quality by ensuring the print medium remains in contact with the rollers and preventing smearing from the support structure, thus enhancing print quality.
Implementation Method 1
the core includes a vacuum manifold that outputs a vacuum force that operates on the second side of the movable print medium through the porous sleeve, moving the movable print medium through the printing system
Implementation Method 2
applying the vacuum force proximate to the second side of the movable print medium such that at least a portion of the movable print medium is deflected causing an increase in a wrap angle of the movable print medium around the vacuum transport rollers
Implementation Method 3
one or more vacuum transport rollers having a porous sleeve rotatable around a non-rotating core
Data Source
AI summary
A method for printing on a print medium is disclosed. The method includes providing a linehead defining one or more print zones and adapted to jet liquid onto the print medium. One or more vacuum transport rollers having a porous sleeve rotatable around a non-rotating core are also provided. At least one vacuum transport roller is disposed adjacent to the second side of the movable print medium, opposite the first linehead, and aligned with a print zone. The core includes a vacuum manifold that outputs a vacuum force that operates on the print medium through the porous sleeve. The print medium is moved through the printing system and a vacuum force deflects the print medium, causing an increase in a wrap angle of the print medium around the vacuum transport roller. Liquid is jetted from the linehead onto the print medium to form a print.