Angled Two-Nip Calender Layout for Lower Soft Roll Thermal Stress
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Solution Overview
Problem
Existing calenders expose soft rolls to high thermal stress and irregularities, particularly when dealing with thick points like seams, leading to inefficient processing and increased material loss due to complex control requirements.
Innovation Solution
A calender design with a hard roll forming nips at an angle less than 180° with two soft rolls, preferably 90°, allows for independent control of line forces in each nip, reducing thermal load on soft rolls and minimizing material loss by enabling one pressure control, and incorporating a thick point sensor to adjust line forces before thick points pass through.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If two soft rolls are used together with another roll to form two nips in one passage, then the desired calendering effect is achieved in one run, but the soft rolls are exposed to high thermal stress and irregularities
Solution Approach 1:
The calendering process is segmented into two independent nips with separate soft rolls, allowing each soft roll to be optimized for specific conditions while the hard roll serves as a common heated element. This segmentation reduces thermal stress on each individual soft roll compared to using a single soft roll for both nips.
Solution Approach 2:
The hard roll is specifically designed with heating capability to provide localized thermal energy only where needed for the calendering process, while the soft rolls remain unheated and are positioned to minimize exposure to thermal stress. This local quality assignment optimizes the thermal management of the system.
2Reliability
If the planes of action of soft roller and hard roller are at an angle less than 180°, then irregularities in one roll gap have less impact on the other roll gap, but the device complexity increases
Solution Approach 1:
The effective planes of the soft rolls are deliberately arranged at asymmetric angles (specifically 90°) relative to each other, creating independence between the two nips. This asymmetric arrangement ensures that irregularities in one roll gap do not directly transfer to the other, improving reliability while maintaining manageable device complexity through a standardized angular configuration.
3Object-affected harmful factors
If the axis of rotation of hard roller is higher than the axis of rotation of soft rollers, then thermal load on soft rollers is reduced by convection, but the device complexity increases
Solution Approach 1:
The hard roll is positioned in a different vertical dimension (higher axis) relative to the soft rolls, creating a three-dimensional arrangement that utilizes convective air flow patterns to reduce thermal load on the soft rolls. This dimensional arrangement allows thermal management through natural convection while maintaining structural integrity and operational simplicity.
4Productivity
If thick points like seams pass through the calender, then material processing continues, but material loss increases due to complex control requirements
Solution Approach 1:
A thick point sensor detects seams and irregularities before they reach the nips, allowing the control system to preemptively adjust line forces and prepare the calender for upcoming thick points. This preliminary action enables continuous processing while minimizing material loss by preventing damage before it occurs.
Solution Approach 2:
The thick point sensor provides real-time feedback to the control system, which automatically adjusts the line forces in response to detected irregularities. This feedback mechanism allows the calender to adapt to varying material conditions, maintaining continuous processing while reducing material loss through automated control.
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 design reduces thermal stress on soft rolls, minimizes material loss, and simplifies control processes by allowing independent regulation of line forces, ensuring efficient passage of thick points without damaging the calender.
Implementation Method 1
the thermal load on the soft rollers is reduced by the hard roller due to convection
Data Source
Figure 1~4
Figure 5
AI summary
The invention relates to a calender (100) for treating a product web (1), comprising several rolls (2, 3, 4), wherein at least one hard roll (3) is provided, which together with two soft rolls (2, 4) forms two nips (5, 6), wherein the hard roll (3) is preferably heated, wherein the planes of action (7, 8) of the soft rolls (2, 4) with the hard roll (3) are located at an angle y relative to one another, said angle being smaller than 180º.