WOT Transposition for Uniform Elastomeric Wound Rolls
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Solution Overview
Problem
Winding processes for elastomeric and low modulus films result in non-uniform material properties throughout the wound roll, leading to variations in elastic properties and increased waste and downtime in processing lines, especially when printing is involved, due to permanent changes in material attributes caused by stored stresses.
Innovation Solution
A modified winding procedure using 'WOT Transposition' adjusts the wound-on-tension (WOT) profile to compensate for deficits in tension across the roll diameter, ensuring uniform material properties through the use of a computer model based on Zbigniew Hakiel's nonlinear model for wound roll stresses, implemented in a winder computer program.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a constant WOT winding profile is used, then the winding process is simple and fast, but the material properties become non-uniform throughout the wound roll
Solution Approach 1:
The patent applies dynamics by transitioning from a static constant WOT profile to a dynamic controlled WOT profile that varies with roll diameter. The WOT is adjusted in real-time based on the current diameter of the wound roll, allowing the tension to adapt as layers are added. This dynamic adjustment ensures uniform material properties throughout the roll while maintaining efficient winding speeds.
Solution Approach 2:
The patent changes the WOT parameter from a constant value to a variable value that depends on roll diameter. By modifying the WOT parameter dynamically during the winding process, the system achieves uniform material properties throughout the wound roll. The controlled WOT profile adjusts tension based on the accumulating layers, preventing the non-uniformity that occurs with constant tension winding.
2Strength
If high tension is applied during winding to create a hard roll, then the roll structure is strong, but permanent changes occur in material properties of elastomeric and delicate materials
Solution Approach 1:
The patent applies local quality by adjusting the WOT based on the specific requirements of different materials and different positions in the winding process. For elastomeric and delicate materials, the controlled WOT profile applies lower tension compared to hard rolls, preventing permanent material property changes. The system tailors the tension locally to the material type and roll diameter, ensuring both structural integrity and material property consistency.
Solution Approach 2:
The patent uses dynamics to create a controlled WOT profile that adapts to material characteristics. Rather than applying constant high tension, the system dynamically adjusts tension based on material type and roll diameter. This dynamic approach allows the roll to achieve sufficient hardness for handling while preventing the permanent material property changes that occur with excessive tension on elastomeric and delicate materials.
3Manufacturing precision
If variable WOT control is implemented to achieve uniform properties, then material consistency improves, but the control system becomes more complex
Solution Approach 1:
The patent implements feedback by using a computer model that continuously calculates the required WOT based on the current roll diameter and material properties. The system monitors the winding process and adjusts the WOT in real-time to maintain uniform material properties. This feedback mechanism automates the complex control required for variable WOT, reducing the burden on operators while achieving precise uniformity.
Solution Approach 2:
The patent introduces a computer model as an intermediary between the winding process and the control system. This intermediary calculates the optimal WOT profile based on Hakiel's nonlinear model, translating complex theoretical requirements into practical control signals. The computer model acts as a mediator that simplifies the implementation of variable WOT control by handling the complex calculations automatically.
4Device complexity
If constant WOT is used for simplicity, then the control system remains simple, but waste and downtime increase due to property variations
Solution Approach 1:
The patent applies self-service by implementing an automated computer-controlled system that manages the variable WOT profile without requiring constant human intervention. The system self-adjusts the tension based on roll diameter and material properties, maintaining uniform material properties throughout the winding process. This automation reduces waste and downtime by preventing property variations that would otherwise require manual adjustment or result in rejected rolls.
Data Source
AI summary
A winding procedure has been developed that results in substantially uniform material properties from the outside diameter to the core of a wound roll of elastomeric webs produced by vertical film lamination (VFL) or stretch bond lamination (SBL) or as registered film. The web material is wound onto the roll in accordance with a wound on tension (WOT) profile that varies with the diameter of the wound web in a manner that was calculated using WOT transposition that is based on a modified version of Hakiel's nonlinear model for wound roll stresses. A constant WOT winding profile is corrected to obtain a compensated WOT winding profile that can be employed to wind the material into a roll that exhibits properties (including MD stress in the web) that are substantially uniform thru-roll. This resulting controlled winding technique has immediate application for webs that are converted for child care products, adult care products, and infant care products.