Fiber Web Caliper Control via Inner Layer Compensation
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Solution Overview
Problem
Fiber web production lines often result in caliper values exceeding target values, leading to significant economic and environmental drawbacks due to bulkiness and caliper losses during reeling and winding, particularly in board manufacturing.
Innovation Solution
A method to control the caliper of fiber webs by adjusting production line parameters such as web speed, headbox-flow, coating weight, and calender nip load, measured through on-line sensors and sample data, to ensure the parent roll and customer rolls have a constant or nearly constant caliper, with increased caliper values for inner layers to compensate for bulk loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the fiber web is produced with constant caliper values to meet target specifications, then manufacturing precision is maintained, but caliper losses during reeling cause the final product to fall below target values
Solution Approach 1:
The patent applies preliminary action by increasing the caliper of the fiber web before reeling. The control device adjusts production parameters (headbox flow, web speed, calender nip load) in advance during the reeling phase to compensate for anticipated bulk loss, ensuring the final caliper meets target values after compression during winding.
Solution Approach 2:
The patent implements dynamics by making the caliper control adaptive rather than static. The control device continuously monitors actual caliper values and dynamically adjusts production parameters based on the current parent roll diameter and phase (inner layers vs. outer layers), allowing real-time optimization to counteract varying compression effects during reeling.
2Manufacturing precision
If the fiber web caliper is increased to compensate for reeling bulk loss, then final caliper target values are achieved, but raw material usage and energy consumption increase
Solution Approach 1:
The patent applies local quality by differentiating caliper control for different regions of the parent roll. The control device applies different target caliper values for inner layers versus outer layers during reeling, adjusting parameters locally based on the specific phase of winding to achieve uniform final caliper while minimizing overall material usage.
Solution Approach 2:
The patent implements parameter changes by dynamically modifying production parameters (headbox flow rate, web speed, calender nip load) based on the current reeling phase and parent roll diameter. This allows precise control of web caliper at different stages, compensating for bulk loss only when and where needed rather than maintaining uniformly increased caliper throughout.
3Manufacturing precision
If production parameters are adjusted frequently to maintain constant caliper, then manufacturing precision is improved, but device complexity and control system complexity increase
Solution Approach 1:
The patent implements feedback by using on-line caliper measurement devices to continuously monitor actual web caliper values during production. The control device receives this feedback and automatically adjusts production parameters to maintain target caliper values, creating a closed-loop control system that improves precision without requiring complex manual intervention.
Solution Approach 2:
The patent applies self-service by enabling the control system to automatically regulate caliper based on measured values and pre-programmed rules. The system monitors its own performance through on-line measurements and self-adjusts parameters (headbox flow, web speed, calender load) without external intervention, maintaining precision while keeping the control architecture manageable.
Data Source
AI summary
To minimize the cost of a fiber web due to the web, particularly a board web, being manufactured overly thick to compensate for loss of caliper in the reel-up, the web is made thicker just for the inner layers of what will become a parent roll. The caliper of the web is measured as or after it is unwound. A caliper curve of the parent roll as a function of the diameter of the parent roll is calculated as a function of the diameter of the parent roll and/or the customer roll. The fiber web is adjusted by changing running parameters of the production line: web speed i.e. production speed, headbox-flow, head-box consistency, coating weight of the coating paste or calender nip load.