Printer Edge Hold Down Tensioned Band Substrate Flatness
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Solution Overview
Problem
Conventional flatbed printers face challenges in maintaining the accuracy and precision of ink droplet placement on substrates as they move through the printer, leading to inconsistent print quality due to substrate movement and defects, which conventional vacuum belt assemblies often struggle to address.
Innovation Solution
The implementation of edge hold down (EHD) systems using tensioned bands, affixed between entry and exit tension assemblies, to apply pressure and keep the substrate flat against the transfer belt, potentially supplemented by a vacuum belt assembly depending on substrate characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional flatbed printer allows the substrate to simply sit on the transfer belt, then the device complexity is low, but the substrate moves during printing resulting in poor droplet accuracy
Solution Approach 1:
The hold-down mechanism is segmented into multiple independent rollers positioned at different locations along the substrate. Each roller can apply pressure independently to specific regions, allowing precise control of substrate flatness without requiring a complex monolithic pressing mechanism.
Solution Approach 2:
A vacuum belt assembly is introduced as an intermediary between the transfer belt and the substrate. The vacuum belt creates negative pressure to secure the substrate to the transfer belt, preventing movement during printing while maintaining system simplicity.
2Manufacturing precision
If a tensioned band is used to hold the substrate flat against the transfer belt, then substrate flatness is improved, but friction increases causing the substrate to slip
Solution Approach 1:
A vacuum belt assembly using pneumatic principles is employed to hold the substrate flat against the transfer belt. The vacuum creates negative pressure that secures the substrate without requiring high friction, thereby preventing slipping while maintaining flatness.
Solution Approach 2:
The surface characteristics of the vacuum belt are optimized to create sufficient negative pressure. By changing the pneumatic parameters (vacuum level, belt speed), the system achieves substrate flatness without excessive friction that would cause slipping.
3Strength
If the tensioned band is made stiffer to resist distortion, then the band can better hold the substrate flat, but the band becomes difficult to install and adjust
Solution Approach 1:
The tensioned band is designed with dynamic characteristics that allow it to be flexible during installation and adjustment, then become stiff when tensioned. The band can be easily positioned and adjusted in the relaxed state, and gains the required stiffness and distortion resistance when properly tensioned between the hold-down rollers.
Solution Approach 2:
The physical state of the tensioned band changes from flexible (during installation) to stiff (when tensioned). By controlling the tension parameter, the band transitions between easy-to-manipulate and structurally-rigid states, resolving the contradiction between ease of installation and resistance to distortion.
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
Ensures high print quality by maintaining substrate flatness and preventing ink droplet misplacement, even with substrates having defects like curls or notches, while minimizing friction-induced slipping.
Implementation Method 1
The tensioned band holds the substrate substantially flat against a transfer belt during printing by applying pressure to the surface of the substrate
Implementation Method 2
in some embodiments, a vacuum belt assembly may be necessary because the tensioned band creates too much friction, which causes the substrate to slip on the transfer belt
Data Source
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AI summary
Edge hold down (EHD) systems are described herein that enable high print quality to be achieved more consistently, particularly when using substrates that are rigid or include one or more defects. Each EHD system includes a tensioned band for holding down an edge of a substrate as it passes through a printer assembly without impacting the print area. The tensioned band can be affixed between an entry tension assembly and an exit tension assembly disposed downstream of the entry tension assembly in the media feed direction. The tensioned band holds the substrate substantially flat against a transfer belt during printing by applying pressure to the surface of the substrate. The tensioned band generally contacts the surface of the substrate substantially proximate to an outer edge that is parallel to the media feed direction.