Interferometric Keyhole Monitoring for Stable Laser Welding
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Solution Overview
Problem
Existing laser welding technologies face challenges in controlling the phase change region (PCR) during keyhole welding, leading to instability, voids, and porosity due to the turbulent and stochastic nature of the keyhole formation, which complicates weld quality verification and system contamination.
Innovation Solution
Implementing low-coherence interferometry to characterize keyhole dynamics by directing multiple imaging beams at various positions and angles relative to the PCR, using an interferometry output processor to determine keyhole characteristics such as depth, width, and stability, allowing for real-time feedback control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If keyhole welding is used to achieve higher aspect ratio features and deeper penetration, then the depth of the phase change region increases, but the keyhole becomes unstable and turbulent leading to voids and porosity
Solution Approach 1:
The patent employs real-time optical monitoring of the keyhole using interferometry to detect keyhole dynamics and morphology. This feedback information is used to adjust welding parameters (power, speed, focus position) to maintain stable keyhole formation while achieving deep penetration, thereby preventing voids and porosity
Solution Approach 2:
The patent dynamically changes welding parameters (laser power, welding speed, focal position) based on real-time keyhole measurements to optimize the balance between penetration depth and keyhole stability, preventing turbulence while maintaining deep phase change region
2Length of moving object
If laser power is increased to maintain keyhole formation at greater depths, then penetration depth increases, but spatter increases contaminating nearby components
Solution Approach 1:
The real-time optical monitoring system detects keyhole morphology and stability, providing feedback to adjust laser power and welding parameters to maintain adequate penetration while minimizing spatter generation and contamination of surrounding components
3Loss of information
If conventional imaging methods are used to monitor the weld, then the system complexity remains low, but the ability to track the phase change region in real-time is insufficient
Solution Approach 1:
The patent uses optical interference phenomena (phase transitions of light waves) to create an imaging system that can penetrate and visualize the keyhole interior in real-time, providing detailed information about the phase change region without requiring overly complex imaging hardware
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
Enhances weld quality by providing dynamic and simultaneous tracking of keyhole features, reducing instability and porosity, and enabling closed-loop process control to improve the consistency and reliability of laser welding.
Implementation Method 1
an optical combiner that combines the reflection component and at least another component of the imaging light to produce an interferometry output
Implementation Method 2
an optical combiner that combines the reflection component and at least another component of the imaging light to produce an interferometry output, the interferometry output based on a path length taken by the first component and the reflection component compared to a path length taken by the at least another component of the imaging light
Implementation Method 3
the more dynamic and unstable process of keyhole welding is used to allow the conversion of optical to thermal energy to occur deeper in the material
Data Source
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AI summary
A method, apparatus, and system are provided to monitor and characterize the dynamics of a phase change region (PCR) created during laser welding, specifically keyhole welding, and other material modification processes, using low-coherence interferometry. By directing a measurement beam to multiple locations within and overlapping with the PCR, the system, apparatus, and method are used to determine, in real time, spatial and temporal characteristics of the weld such as keyhole depth, length, width, shape and whether the keyhole is unstable, closes or collapses. This information is important in determining the quality and material properties of a completed finished weld. It can also be used with feedback to modify the material modification process in real time.