Calender
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Solution Overview
Problem
Existing calenders expose soft rolls to high thermal stress and irregularities, particularly when dealing with thick points, leading to inefficiencies and damage during the calendering process.
Innovation Solution
A calender design with a hard roll forming nips at an angle of less than 180° with two soft rolls, where the planes of action are preferably 90° apart, allowing independent control of line forces and reducing thermal load on soft rolls through convection, and incorporating a thick point sensor and control device to manage line forces during thick point passage.
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 nip zones formed by a three-roll arrangement. The first nip (between hard roll and first soft roll) and second nip (between hard roll and second soft roll) operate with independent line forces, allowing separate control of thermal and mechanical parameters for each zone. This segmentation enables one soft roll to be protected from thermal stress while the other performs calendering.
Solution Approach 2:
The hard roll serves as a thermal mediator between the heated zone and the soft rolls. By positioning the hard roll to form nips with both soft rolls at angles less than 180°, the hard roll transfers heat to the material web in a controlled manner while the soft rolls remain relatively cool, protecting them from excessive thermal stress.
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 three rolls are arranged asymmetrically with the planes of action of the soft rollers and hard roller forming angles γ1 and γ2 less than 180° with each other. This asymmetric configuration ensures that irregularities in one roll gap do not directly transfer to the other gap, improving process stability while maintaining a relatively simple mechanical structure.
3Adaptability or versatility
If line force in one nip is controlled independently of the other nip, then the ability to handle thick points is improved, but the control system complexity increases
Solution Approach 1:
The line forces in the two nips are made dynamically independent and controllable. The first line force and second line force can be adjusted separately based on material conditions, allowing the system to adapt to thick points, seams, or variations in web thickness. This dynamic control capability enables responsive handling of material irregularities without requiring complex mechanical adjustments.
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 minimizes thermal stress on soft rolls, reduces material loss, and simplifies control processes by allowing independent regulation of line forces, thereby enhancing the calendering efficiency and reducing rejects.
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.