Low-Coherence Interferometry for Keyhole Welding 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, which affects weld quality and productivity, with current imaging solutions being limited to pre- or post-weld monitoring.
Innovation Solution
The use of low-coherence interferometry to direct multiple imaging beams into the PCR, measuring keyhole characteristics such as length, width, depth, and shape in real time, allowing for dynamic control of the welding process through feedback mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If keyhole welding is used to achieve higher aspect ratio features, then the depth of penetration is improved, but the stability of the process deteriorates due to turbulent and stochastic keyhole dynamics
Solution Approach 1:
The patent implements real-time optical monitoring of keyhole dynamics during laser welding, capturing images at high frame rates to track keyhole position, shape, and stability. This feedback information is used to dynamically adjust welding parameters (power, speed, focus) to maintain stable keyhole formation and prevent defects, thereby resolving the contradiction between achieving deep penetration and maintaining process stability.
Solution Approach 2:
The patent dynamically changes welding parameters (laser power, welding speed, focal position) based on real-time keyhole monitoring to optimize the balance between penetration depth and process stability. By adjusting these parameters in response to observed keyhole behavior, the system maintains stable welding at high aspect ratios without sacrificing penetration depth.
2Device complexity
If imaging solutions monitor regions before or after the PCR, then the system complexity is reduced, but the measurement precision of keyhole dynamics deteriorates
Solution Approach 1:
The patent introduces an optical intermediary system (lens, mirrors, beam splitters) that enables indirect observation of the keyhole through the welding head without requiring direct line-of-sight access. This intermediary optical path allows real-time monitoring of keyhole dynamics while keeping the imaging system relatively simple and integrated into the existing welding setup.
Solution Approach 2:
The patent designs an imaging system that can simultaneously monitor multiple aspects of the welding process (keyhole position, shape, spatter, weld pool) through a single integrated optical path. This multi-functional capability achieves high measurement precision without proportionally increasing system complexity, as one imaging system serves multiple diagnostic purposes.
3Manufacturing precision
If real-time monitoring of keyhole dynamics is implemented, then the manufacturing precision of weld quality is improved, but the device complexity increases due to additional imaging and processing components
Solution Approach 1:
The patent implements a feedback control system where real-time images of keyhole dynamics are processed to extract quantitative parameters (keyhole position, depth, width) that directly indicate weld quality. These parameters feed back to the control system to adjust welding parameters, ensuring consistent high-quality welds. The feedback mechanism transforms complex imaging data into simple quality indicators that drive process control.
Solution Approach 2:
The patent extracts only the most critical keyhole parameters (position, depth, width, stability) from the full imaging data stream for quality assessment and control. By focusing on these essential features rather than processing all image data, the system achieves high manufacturing precision while minimizing the computational and hardware complexity required for image processing.
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 precise monitoring and control of keyhole dynamics, reducing weld defects and improving the quality and productivity of laser welding processes by providing real-time feedback for process adjustments.
Implementation Method 1
directing an interferometry measurement beam (including, for example, a low-coherence interferometry measurement beam) into the PCR and surrounding area
Implementation Method 2
combining 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
Data Source
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.