OCT-Guided Laser Weld Bead Control for Consistent Attachment Area
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Solution Overview
Problem
Current laser welding processes for metallic bar-type conductors, such as copper or aluminum, face challenges in ensuring a consistently large attachment area due to variations in surface reflectivity, contamination, positioning errors, and spatter formation, leading to inefficient energy input and complex reworking of defective welds.
Innovation Solution
The method employs optical coherence tomography (OCT) for real-time scanning of the melt pool and weld bead during the laser welding process, allowing for closed-loop control of welding parameters based on actual geometry deviations from target geometries, enabling immediate adjustments to achieve a sufficient attachment area without destructive testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser welding is performed with constant power and time, then the welding process is simple and fast, but the attachment area varies due to surface reflectivity, contamination, positioning errors, and spatter formation
Solution Approach 1:
The patent implements real-time feedback control by monitoring the melt pool geometry during laser welding using optical sensors. The actual melt pool dimensions are measured and compared to target values, and welding parameters (power, speed, position) are dynamically adjusted to maintain consistent attachment area despite variations in surface conditions or positioning errors
Solution Approach 2:
The welding system transitions from static constant-power welding to dynamic welding where parameters are continuously adjusted based on real-time melt pool monitoring. The laser power, welding speed, and beam position are made variable to compensate for spatter formation, surface reflectivity changes, and positioning deviations, ensuring consistent attachment area
2Productivity
If the attachment area is checked only subsequently by destructive testing or CT/x-ray technology, then the welding process is fast, but reworking defective parts is complex and time-consuming
Solution Approach 1:
The system performs preliminary quality assessment by monitoring melt pool geometry in real-time during welding. Defects are detected and corrected during the welding process itself rather than after completion, preventing defective welds before they occur and eliminating the need for subsequent destructive testing or complex rework
Solution Approach 2:
Real-time feedback from optical monitoring enables immediate detection of abnormal melt pool behavior indicating potential defects. The system responds by adjusting welding parameters to correct the issue during processing, avoiding the need for post-weld inspection and rework
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 enables non-destructive, real-time monitoring and control of the laser welding process, ensuring a consistently large attachment area and reducing the complexity of reworking defective parts by automatically adjusting welding parameters, thus improving the efficiency and quality of the welds.
Implementation Method 1
an optical coherence tomography (OCT) measurement beam is directed by the laser scanner at the two end faces, in particular at the melt pool and/or the melt bead and/or the weld bead
Implementation Method 2
a processing laser beam that is directed at end faces of the workpieces arranged next to one another in order to melt a melt pool at the two end faces
Implementation Method 3
The end faces are melted by the heat that is introduced and, after solidification, are connected to one another via a re-solidified melt bead
Data Source
AI summary
A method for monitoring and/or controlling in a closed loop a laser welding process for welding together two workpieces of metallic material includes, during the laser welding process, scanning a melt pool and/or a melt bead using an optical coherence tomography (OCT) measurement beam in at least one line scan, determining an actual geometry of the melt pool and/or the melt bead based on the at least one line scan, and setting at least one welding parameter controlled in the closed loop based on a deviation of the actual geometry from a target geometry of the melt pool and/or the melt bead.