Laser Weld Penetration Sensing with Orbital Measurement Light
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Solution Overview
Problem
Existing laser welding devices face inaccuracies in measuring weld penetration depth due to optical axis misalignment between laser light and measurement light, particularly when components are displaced by vibrations, leading to incorrect depth measurements.
Innovation Solution
A laser welding device that changes the irradiation position and optical axis of measurement light to move within a radius smaller than half the spot diameter of the laser light, allowing multiple measurements along a spiral or orbital path to accurately determine the weld penetration depth, using a determiner to filter out abnormal values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the measurement light and laser light are coaxially overlapped to measure weld penetration depth, then the measurement can be performed simultaneously with welding, but optical axis misalignment occurs due to vibrations causing measurement inaccuracy
Solution Approach 1:
The patent transitions from a single-point coaxial measurement (one-dimensional alignment) to a two-dimensional scanning measurement approach. The measurement light scans the keyhole bottom in the radial direction while the irradiation position moves along the welding path, creating a measurement plane that captures depth information from multiple positions, thereby resolving the alignment sensitivity issue.
Solution Approach 2:
The patent introduces dynamic scanning of the measurement light position rather than a static coaxial measurement. The irradiation position is changed along the welding path and the measurement light scans radially, allowing the system to adapt to vibrations and maintain measurement accuracy through continuous positional adjustment.
2Ease of operation
If the optical axis of measurement light is misaligned frontward in the welding direction, then the measurement light applies to a curved portion with shallower penetration, but the measured depth becomes shallower than the actual deepest part
Solution Approach 1:
The patent adds radial scanning dimension to the measurement process. Instead of relying on perfect axial alignment, the measurement light scans across the keyhole bottom in the radial direction, ensuring that the deepest point is captured regardless of axial misalignment. This transforms a one-dimensional axial measurement problem into a two-dimensional measurement that compensates for alignment errors.
Solution Approach 2:
The patent changes the measurement parameters by introducing radial position variation and scanning speed control. By adjusting the radial scanning range and speed, the system ensures comprehensive coverage of the keyhole bottom, allowing accurate depth measurement even when the optical axis is misaligned in the welding direction.
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 enhances the accuracy of weld penetration depth measurement by ensuring the measurement light is applied to the deepest part of the keyhole, reducing errors from optical axis misalignment and external disturbances.
Implementation Method 1
the measurement light reflected on the bottom of the keyhole is caused to enter an optical interferometer via a beam splitter. Because the optical interferometer can measure the optical path length of the measurement light, the depth of the keyhole obtained from the measured optical path length is identified as the weld penetration depth
Implementation Method 2
a first focusing lens 22 and a second focusing lens 24, the irradiation positions of laser light L and measurement light S are changed
Data Source
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AI summary
A laser welding device (10) for welding a weld part (35) with laser light (L) includes: a laser emitting head (20) overlapping the laser light (L) and a measurement light (S) coaxially with each other and applying the laser light (L) and the measurement light (S) to the weld part (35), the measurement light (S) having a wavelength different from a wavelength of the laser light (L); a first parallel plane plate and a second parallel plane plate, changing an irradiation position of the measurement light (S) such that the irradiation position orbitally move around a center of rotation that moves on a predetermined welding path in a radius of rotation that is smaller than 1/2 of a spot diameter of the laser light (L); a measuring instrument (14) repeatedly measuring a weld penetration depth of the weld part (35) based on the measurement light (S) that is emitted from the laser emitting head (20) and is reflected on the weld part (35) while the measurement light (S) is being orbitally moved; and a determiner (17) determining the weld penetration depth of the weld part (35) using a plurality of measured values of the weld penetration depth, the plurality of measured values being measured by the measuring instrument (14) within a fixed time period while shifting a start time point of the fixed time period.