Indirect Strip Thickness Calculation in Multi-Stand Rolling Mills
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Solution Overview
Problem
In multi-stand cold rolling mills, strip thickness errors often go unnoticed until the last rolling stand, leading to delayed and incomplete corrections, as intermediate stands lack thickness measurement, and proposed solutions like additional measuring devices are impractical due to cost or imprecision.
Innovation Solution
An operating method that calculates strip thickness indirectly using inlet and outlet speed measurements, modeling overfeed based on circumferential roll speed, allowing for real-time correction of strip thickness errors across all rolling stands without the need for additional thickness measuring devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thickness measuring devices are arranged behind each roll stand, then strip thickness can be measured at each intermediate stand, but the cost increases significantly
Solution Approach 1:
The patent uses speed measurements as an intermediary parameter to indirectly determine strip thickness. Instead of measuring thickness directly at each stand, the system measures strip speed at inlet and outlet of each roll stand and uses the continuity equation (mass conservation) to calculate thickness. This mediator approach avoids installing expensive thickness measuring devices at every location while still achieving the measurement objective.
Solution Approach 2:
The patent replaces mechanical thickness measuring devices with a computational approach based on speed measurements and mathematical modeling. The system substitutes physical measurement infrastructure with a combination of speed sensors, overfeed modeling, and continuity equation calculations, thereby reducing hardware complexity and cost.
2Device complexity
If thickness measurement is only performed at the last rolling stand, then the system is simpler, but strip thickness errors are detected too late for effective correction
Solution Approach 1:
The patent implements preliminary detection of strip thickness errors at each intermediate roll stand by calculating thickness in real-time using speed measurements. Instead of waiting until the last stand to detect errors, the system continuously monitors and calculates thickness at each stage, enabling early detection and immediate correction before the strip progresses further through the rolling train.
Solution Approach 2:
The system establishes a continuous feedback loop where speed measurements at each roll stand inlet and outlet are used to calculate strip thickness, which is then fed back to control systems for immediate adjustment. This real-time feedback mechanism enables dynamic correction of thickness deviations at each intermediate stand rather than delayed correction at the end.
3Device complexity
If rolling force and spring constant are used to calculate strip thickness, then no additional measuring devices are needed, but the measurement precision is insufficient
Solution Approach 1:
The patent changes the measured parameters from rolling force and spring constant to strip speed at inlet and outlet of each roll stand. By measuring speed instead of force and using the continuity equation, the system achieves higher measurement precision. The speed measurements directly reflect the actual strip flow and thickness changes, whereas force-based calculations involve multiple assumptions and indirect relationships that reduce accuracy.
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
Enables immediate and precise correction of strip thickness errors throughout the rolling train, improving dimensional accuracy and operational efficiency by tracking section thickness and adjusting roll stands dynamically.
Implementation Method 1
the strip thickness being determined for the roll stand under consideration on the basis of the entry thickness, the entry-side speed of the strip and the exit-side speed of the strip
Data Source
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AI summary
A strip (6) is fed to one of (2 - 5) the rolling stands (1 - 5) (rolling stand in question) of a multi-stand rolling mill with a known inlet thickness (d1 - d4) and exits the rolling stand in question (2 - 5) with a strip thickness (d2 - d5). Measurement parameters (vR, vW) are determined that are characteristic of the inlet-side velocity (v1 - v4) of the strip (6) and the outlet side velocity (v2 - v5) of the strip (6) with respect to the rolling stand in question (2 – 5). By means of the measurement parameters (vR, vW), the inlet-side velocity (v1 - v4) of the strip (6) and the outlet side velocity (v2 - v5) of the strip (6) are determined with respect to the rolling stand in question (2 – 5). By means of the inlet thickness (d1 - d4), the inlet-side velocity (v1 - v4) of the strip (6) and the outlet side velocity (v2 - v5) of the strip (6), the strip thickness (d2 - d5) is determined with respect to the rolling stand in question (2 – 5). Taking into account the determined strip thickness (d2 - d5), further measures are taken. The measurement parameter (vW) for the inlet-side velocity (v1 - v4) of the strip (6) is the roller peripheral velocity (vW) of the rolling stand (1 – 4) directly prior to the rolling stand in question (2 – 5). Alternatively or in addition, the measurement parameter (vW) for the outlet-side velocity (v2 – v5) of the strip (6) is the roller peripheral velocity (vW) rolling stand in question (2 – 5). The peripheral precession of the strip (6) in the respective rolling stand (2 – 5) is modeled. The respective velocity (v1 - v5) of the strip (6) is determined using the respective roller peripheral velocity (vR) and the peripheral precession of the strip (6) in the respective rolling stand (1 - 5).