Optical Flatness Measurement for Metallic Strip
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Solution Overview
Problem
Existing methods for measuring the flatness and residual stresses in metallic flat products, such as steel strips, face challenges in accuracy due to contamination, cooling effects, and insufficient precision, especially in hot rolling and tensionless conditions.
Innovation Solution
A method involving bending the metallic flat product to form an arc, allowing for non-contact measurement of the contour and subsequent determination of flatness and residual stresses, using optical distance measuring devices and a computation unit to analyze the actual bending radii and calculate stress, while maintaining the product tension-free and pressure-free during measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If non-contactless measuring methods (e.g., pressure-sensitive measuring rollers) are used, then contact with the measuring roller is established, but the flat product is cooled and measuring rollers are contaminated by scale or dirt, reducing measurement reliability
Solution Approach 1:
The patent replaces mechanical contact-based measurement systems with an optical measurement system. A laser beam is projected onto the flat product surface, and a camera captures the reflected light pattern. The flatness is determined by analyzing the deformation of the light pattern, eliminating the need for physical contact between measuring rollers and the flat product, thereby avoiding cooling effects and contamination.
Solution Approach 2:
The patent introduces light (laser beam) as an intermediary between the measurement system and the flat product. The laser beam serves as a non-contact probe that interacts with the flat product surface, and the camera acts as an intermediary to capture and transmit the measurement information, enabling accurate flatness measurement without direct mechanical contact.
2Measurement precision
If non-contactless flatness measuring is performed, then a defined minimum tension is required, but measuring accuracy is adversely affected and flatness of tensionless strip head or strip foot cannot be determined
Solution Approach 1:
The optical measurement system replaces mechanical tension-based measurement methods. Since the measurement is based on optical pattern analysis rather than mechanical force application, no minimum tension is required. This enables accurate flatness measurement of tensionless strip heads and strip feet that cannot be measured by conventional contact methods.
3Reliability
If contactless measuring methods are used, then measurement reliability is improved, but measurement accuracy is insufficient
Solution Approach 1:
The patent employs an optical measurement system that combines the advantages of both contactless and high-precision methods. By using laser projection and camera-based pattern analysis, the system achieves contactless measurement while maintaining high accuracy through sophisticated optical signal processing and mathematical evaluation of the light pattern deformation.
Solution Approach 2:
The patent transitions from one-dimensional point measurements to two-dimensional field measurements by projecting a laser line or pattern across the flat product surface and capturing the entire pattern with a camera. This dimensional expansion provides comprehensive surface information and enables more accurate flatness assessment across the entire width of the flat product.
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 approach enhances the accuracy and reliability of flatness and residual stress measurements, enabling better quality control and precise processing, including the ability to assess and correct flatness in real-time during rolling and account for residual stresses in further processing steps.
Implementation Method 1
The contour is measured, in particular by measuring the actual bending radii r(y), in the region of the arc of the bent flat product in a number of positions (y)
Data Source
AI summary
A method and apparatus for flatness measuring and measuring of residual stresses in a metallic flat product (1): The method includes bending the flat product (1) in a bending device (3) such that a planar flat product (1) forms an arc (5) with a target bending radius r0 after bending; measuring the contour and the actual bending radii r(y), in the region of the arc (5) of the bent flat product (1) at a plurality of positions along the width direction of the flat product (1); and determining the flatness of the flat product (1) taking into account the measured contour of the bent flat product (1).