Laser Weld Inspection Using Thermal and Plasma Signal Comparison
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Solution Overview
Problem
Current laser welding quality inspection methods struggle to accurately detect minute welding abnormalities due to overlapping signal intensities of thermal radiation and plasma light, leading to erroneous determinations.
Innovation Solution
A method and apparatus that compare the signal intensities of thermal radiation light and plasma light during laser welding, calculating a difference signal to determine welding abnormalities by identifying peaks exceeding a preset reference value, thereby enhancing detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the peak intensity or integrated intensity of welding light (thermal radiation light, plasma light, and laser reflection light) is used for determination, then clear welding abnormalities can be detected, but minute welding abnormalities cannot be accurately determined
Solution Approach 1:
The patent segments the welding light into three distinct components: thermal radiation light, plasma light, and laser reflection light. By using multiple light-receiving units (first, second, and third light-receiving units respectively), each component is detected separately. This segmentation allows the system to analyze the temporal characteristics of each light type independently, enabling accurate detection of minute welding abnormalities that cannot be identified when using only the peak or integrated intensity of combined welding light.
2Measurement precision
If only peak intensity or integrated intensity of welding light is measured, then the inspection method is simple, but the detection accuracy for minute abnormalities is insufficient
Solution Approach 1:
The patent divides the inspection method into multiple stages: first, segment the welding light into three components using separate light-receiving units; second, calculate temporal derivatives (first and second derivatives) of each light component's intensity over time; third, integrate these derivatives to generate determination values. This segmented approach, while more complex than simple peak intensity measurement, provides significantly enhanced detection accuracy for minute abnormalities by analyzing the temporal evolution of each light component.
Solution Approach 2:
The patent introduces dynamic analysis by calculating the first and second temporal derivatives of the intensity of each light component. Instead of using static measures like peak intensity or integrated intensity, the system evaluates how the intensity changes over time (first derivative) and how the rate of change evolves (second derivative). This dynamic approach enables the detection of subtle temporal patterns that indicate minute welding abnormalities, improving detection accuracy while maintaining a systematic inspection framework.
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 allows for precise identification of welding abnormalities, even those that were previously undetected, resulting in a higher accuracy rate and reduced erroneous determinations.
Implementation Method 1
acquiring first data indicating a signal intensity of thermal radiation light radiated from the welded portion during the welding
Implementation Method 2
a measurement device that measures the thermal radiation light and the plasma light
Implementation Method 3
acquiring second data indicating a signal intensity of plasma light radiated from the welded portion during the welding
Data Source
AI summary
A laser welding quality inspection method of a welded portion between a joining object and a joined object, when the joining object and the joined object are welded by being irradiated with a laser beam, the method includes: acquiring first data indicating a signal intensity of thermal radiation light radiated from the welded portion during the welding; acquiring second data indicating a signal intensity of plasma light radiated from the welded portion during the welding; and determining whether or not the welded portion includes an abnormality based on a comparison between the signal intensity of the thermal radiation light and the signal intensity of the plasma light which are acquired.