Vacuum Pulldown Print Media Wrinkle Reduction
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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 wrinkles and image quality issues, as the print media cannot slip on rollers, resulting in flutes or wrinkles that affect image quality and can smear ink onto support structures.
Innovation Solution
A printing system with two lineheads oriented horizontally, each equipped with a vacuum assembly that deflects the print medium away from the lineheads, using vacuum manifolds to increase the wrap angle around transport rollers, reducing flutter and smearing by maintaining contact and preventing flutes from forming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the print medium is supported by rollers to prevent fluttering, then the print medium stability is improved, but the print medium cannot slip on the rollers causing expansion in crosstrack direction to create flutes or wrinkles
Solution Approach 1:
The patent applies vacuum technology (pneumatics) by using a vacuum assembly with a vacuum manifold disposed opposite the second side of the print medium. The vacuum manifold outputs a vacuum force that deflects the print medium away from the lineheads and increases the wrap angle around transport rollers, allowing the print medium to slip properly during expansion without creating flutes or wrinkles, while still maintaining stability.
2Force
If the print medium wrap around roller produces sufficient friction to prevent sliding, then the print medium is constrained in crosstrack direction, but this constraint causes localized buckling and ripples when the print medium expands
Solution Approach 1:
The vacuum assembly creates a controlled vacuum force that allows the print medium to maintain contact with the roller (providing sufficient friction) while also allowing controlled slipping through the increased wrap angle. This prevents the localized buckling and ripples that occur when friction is too high and prevents uncontrolled sliding that would cause poor print quality.
Solution Approach 2:
The invention changes the geometry of the print medium path by increasing the wrap angle around the transport roller. This dimensional change in the path configuration allows the print medium to accommodate expansion forces without creating localized buckling, as the extended contact area distributes the stress more evenly.
3Quantity of substance
If drying is used frequently to remove moisture from the print medium, then the moisture content is reduced, but this causes changes in dimensional characteristics that adversely affect image quality
Solution Approach 1:
The vacuum assembly allows the system to print multiple colors on the print medium without frequent drying cycles. By maintaining proper contact and allowing controlled slipping through the increased wrap angle, the system can accommodate the dimensional changes from moisture absorption without creating flutes or wrinkles, enabling continuous printing with better image quality.
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 configuration simplifies the print media path, reduces wrinkles and smearing, and enhances image quality by maintaining consistent contact between the print medium and rollers, preventing flutes and improving print quality.
Implementation Method 1
each vacuum assembly having a vacuum manifold disposed opposite the second side of the print medium, where the vacuum manifold outputs a vacuum force proximate to the second side of the print medium
Implementation Method 2
the vacuum manifold outputs a vacuum force proximate to the second side of the print medium such that at least a portion of the print medium is deflected away from the lineheads and towards the aligned transport roller thereby increasing the wrap angle of the print medium around the aligned transport roller
Data Source
AI summary
A printing system for printing on a print medium is disclosed. The printing system comprises two lineheads disposed opposite a first side of the print medium, wherein the two lineheads have a common orientation relative to a horizontal direction. At least one roller is disposed under each linehead and in contact with a second side of the print medium. At least one vacuum assembly is disposed under each linehead, each vacuum assembly having a vacuum manifold disposed opposite the second side of the print medium, where the vacuum manifold outputs a vacuum force proximate to the second side of the print medium such that at least a portion of the second side of the print medium is deflected away from the two lineheads.