Non-Contact Metal Layer Thickness Measurement via Induced Current
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Solution Overview
Problem
In metal object production, measuring the thickness of metal layers on metal sheets or strips is challenging due to differing floating properties during deformation, and existing methods require contact and are not suitable for real-time thickness control during rolling processes.
Innovation Solution
A method utilizing a time-variable magnetic field to induce a current in the metal layer, measuring the secondary magnetic field changes over time, and applying mathematical relationships to determine the layer thickness without contact, allowing for non-invasive, real-time thickness measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If contact-based measurement methods are used to measure metal layer thickness, then measurement can be performed, but the measurement process interferes with the rolling process and cannot achieve real-time control
Solution Approach 1:
The patent replaces contact-based mechanical measurement systems with a non-contact electromagnetic measurement system. The measuring device uses magnetic fields to detect layer thickness without physically touching the metal sheet, allowing real-time measurement during the rolling process without interfering with production.
Solution Approach 2:
The patent introduces magnetic fields as an intermediary between the measurement system and the metal layer. By using magnetic coupling, the measurement can be performed without direct contact, enabling real-time thickness control while maintaining uninterrupted rolling operations.
2Measurement precision
If existing eddy current measurement methods are used, then layer thickness can be measured, but the method requires contact and is not suitable for continuous production monitoring
Solution Approach 1:
The patent replaces contact-based eddy current measurement with a non-contact magnetic field-based measurement system. This substitution enables continuous monitoring during rolling operations while maintaining measurement precision, as the magnetic fields can penetrate and interact with the metal layer without physical contact.
Solution Approach 2:
The patent employs periodic magnetic field excitation to continuously monitor layer thickness during the rolling process. The periodic nature of the magnetic field application allows for real-time data collection and analysis, enabling continuous production monitoring without interrupting the rolling operation.
3Measurement precision
If thickness measurement is performed after rolling, then the measurement can be accurate, but the control loop is too slow for real-time thickness adjustment
Solution Approach 1:
The patent performs thickness measurement during the rolling process itself rather than after completion. By measuring while the metal sheet is still in the rolling mill, the system provides real-time feedback that can be immediately used to adjust rolling parameters, eliminating the time delay associated with post-rolling measurement and enabling real-time thickness 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
Enables accurate, non-contact measurement of metal layer thickness, facilitating real-time thickness control during production, particularly in rolling processes, and allows for simultaneous determination of resistivity, improving production efficiency.
Implementation Method 1
a time variable magnetic field is generated close to the layer. The time variable magnetic field induces a current in the surface of the layer
Implementation Method 2
The induced current produces a secondary magnetic field. The changes over time of the secondary magnetic field are measured outside the layer
Implementation Method 3
the changes of the magnetic field are measured by measuring the voltage across the coil
Data Source
Figure 1~4
Figure 5~8
Figure 9~10
AI summary
The present invention relates to a method and an apparatus for measuring the thickness of a metal layer (2) provided on a metal object (1). The metal layer has a resistivity (p1) that differs from the resistivity (p2) of the metal object. The apparatus comprises a first device (4,7) arranged to generate a magnetic field in close vicinity of the metal layer, and to generate a variation of the magnetic field so that a current is induced in the surface of the metal layer, a second device (5,8) arranged to measure the changes of the magnetic field outside the metal layer due to the induced current during a time period that is longer than the time it takes for the current to propagate through the metal layer, and a computing unit (9) configured to receive the measured changes of the magnetic field and to determine the thickness (d) of the layer based on a mathematical relation between the thickness of the layer and the measured values of the changes of the magnetic field.