Variable Web Tensioning for Printed Media Cockling
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Solution Overview
Problem
Web-fed printing devices face issues with cockling and poor compactness of media when wet ink is wound onto a roller, leading to air trapping and reduced quality of the rolled media due to inadequate tension control based on ink drying rates.
Innovation Solution
A system with a controller that adjusts tension in real-time based on ink drying characteristics, ambient conditions, and ink flux to prevent cockling by varying the tension according to the time taken for the ink to dry, using a tensioner and densitometer to ensure proper winding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If web-fed printing devices operate at high speed, then productivity is improved, but ink drying time becomes insufficient leading to cockling and poor compactness
Solution Approach 1:
The patent applies dynamics by making the tension applied to the media variable rather than constant. The tension is dynamically adjusted based on real-time monitoring of ink drying characteristics, allowing the system to accommodate high printing speeds while preventing cockling. The tensioning mechanism responds continuously to changing conditions during the winding process.
Solution Approach 2:
The patent changes the parameter of tension force based on ink drying rate. By monitoring ink flux and drying characteristics, the system adjusts the tension parameter to optimal values that prevent media deformation. This parameter adjustment ensures that even at high printing speeds where ink drying time is reduced, the media maintains proper flatness and compactness.
2Manufacturing precision
If tension is increased to prevent cockling, then media flatness is improved, but risk of media damage and printing quality degradation increases
Solution Approach 1:
The patent implements feedback control by continuously monitoring ink drying characteristics (ink flux, drying rate) and using this information to adjust tension levels. This closed-loop system ensures tension is increased only to the extent necessary to prevent cockling, rather than applying excessive tension that could damage the media or degrade print quality. The feedback mechanism allows real-time optimization of tension based on actual drying conditions.
Solution Approach 2:
The patent dynamically adjusts the tension parameter based on monitored ink drying rates. When drying is rapid, lower tension suffices; when drying is slow (as at high printing speeds), tension is increased appropriately. This parameter adaptation prevents both cockling and media damage by matching tension levels to actual drying conditions rather than using fixed high tension.
3Device complexity
If constant tension is applied during winding, then device complexity is reduced, but adaptability to varying ink drying rates is poor
Solution Approach 1:
The patent employs feedback control where sensors monitor ink drying characteristics (ink flux, drying rate) and this information feeds back to the tension control system. This allows the relatively simple mechanical tensioning device to adapt automatically to varying drying conditions without requiring complex manual intervention or overly complicated control mechanisms.
Solution Approach 2:
The system performs self-adjustment of tension based on monitored drying conditions. The tension control mechanism automatically responds to ink drying variations without external intervention, making the system adaptable to different printing speeds and environmental conditions while maintaining reasonable device complexity.
Data Source
AI summary
A system (300) is provided having a printer (4) to print printing liquid onto a web (6) of media (8). The system (300) has a winding roller (10) on which to roll the web (6) of media (8) after printing. A tensioner (12) to vary the tension in a portion (14) of the web (6) of media (8) is also provided. The portion (14) is a portion of web which is being rolled onto the winding roller (10). Also provided is controller (16) to control the tensioner (12) to vary the tension based on the time taken for the printed printing liquid on the web (6) of media (8) to dry.