Keyhole Interferometry for Real-Time Laser Weld Stability
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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 affects weld quality and productivity.
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 length, width, depth, and aspect ratio, and applying these measurements to control the welding process.
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 weld defects
Solution Approach 1:
The interferometry measurement beam is directed into the PCR before the keyhole instability causes defects, enabling real-time monitoring and control. The system performs preliminary detection of keyhole characteristics (depth, width, shape) to prevent instability and weld defects before they occur.
Solution Approach 2:
The system uses interferometry to continuously measure keyhole dynamics and provides feedback control to maintain stable keyhole formation. By monitoring the PCR characteristics in real-time, the system can adjust welding parameters to prevent turbulence and instability, ensuring consistent weld quality at deeper penetration levels.
2Reliability
If ex-situ and destructive testing is used for weld quality verification, then weld quality can be confirmed, but productivity decreases and cost increases
Solution Approach 1:
The interferometry system performs preliminary quality verification during the welding process itself, before the weld is completed and cooled. By monitoring keyhole stability and PCR characteristics in real-time, the system can detect potential defects early, eliminating the need for subsequent destructive testing and improving productivity.
Solution Approach 2:
The system replaces mechanical destructive testing with optical interferometry measurement. Instead of physically examining welds after completion, the system uses non-contact optical methods to monitor keyhole dynamics and predict weld quality in real-time, maintaining reliability while dramatically improving productivity.
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 real-time monitoring and control of keyhole stability, reducing internal voids and spatter, and improving the overall productivity of the welding process.
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, 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 2
characterization of morphology, for example, including one or more of length, width, depth, size, shape, and aspect ratio of the keyhole and surrounding material over time by directing an interferometry measurement beam (including, for example, a low-coherence interferometry measurement beam) into the PCR
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.