Laser Weld Penetration Measurement Using Keyhole Depth Filtering
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Solution Overview
Problem
Existing laser welding devices face challenges in accurately measuring weld penetration depth due to diffused reflection and external disturbances, leading to variations in measured values and inability to perform precise measurements.
Innovation Solution
A laser welding device that measures weld penetration depth by overlapping laser and measurement light coaxially, with the measurement light having a different wavelength, and determines the depth based on multiple measured values within a predetermined range or their average, while adjusting the irradiation position to account for optical axis misalignment and external disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If measurement light is used to measure weld penetration depth, then measurement capability is provided, but measurement precision deteriorates due to diffused reflection and external disturbances
Solution Approach 1:
The patent performs multiple measurements (excessive action) and selects only the deepest measured value that falls within the predetermined range from the greatest side, rather than using all measured values or a simple average. This partial selection approach eliminates measurements affected by diffused reflection while capturing the true keyhole depth.
Solution Approach 2:
The system continuously monitors multiple measured values and uses feedback logic to identify and select the deepest value within the predetermined range. This feedback mechanism dynamically adjusts the measurement result based on the distribution of multiple measurements, improving reliability by filtering out erroneous shallow measurements.
2Reliability
If multiple measured values are used to determine weld penetration depth, then measurement reliability improves, but measurement complexity increases
Solution Approach 1:
The patent changes the parameter selection criterion from simple averaging to selecting the deepest value within a predetermined range from the greatest side. This parameter change in the determination logic simplifies the processing while improving reliability, as it requires only comparison and range checking rather than complex statistical analysis.
3Ease of operation
If optical axis misalignment occurs between laser light and measurement light, then device operation becomes simpler, but measurement precision deteriorates
Solution Approach 1:
The patent performs multiple measurements and selects the deepest value within the predetermined range, which compensates for optical axis misalignment. By taking multiple measurements and using the deepest valid value, the system tolerates alignment errors while maintaining measurement precision.
Solution Approach 2:
The measurement system is designed to handle both aligned and misaligned conditions through the same measurement and selection process. The predetermined range approach provides universal applicability regardless of alignment quality, making the system robust to optical axis deviations.
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 allows for accurate measurement of the weld penetration depth by filtering out shallower keyhole depths and ensuring the measurement light reaches the deepest part of the keyhole, reducing the impact of 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
Implementation Method 2
laser light and measurement light are overlapped coaxially with each other to irradiate the inside of a keyhole of a weld part
Data Source
AI summary
A laser welding device includes: an irradiator configured to overlap laser light and measurement light coaxially with each other and apply the laser light and the measurement light to a weld part, a wavelength of the measurement light being different from a wavelength of the laser light; a measuring instrument configured to repeatedly measure a weld penetration depth of the weld part based on the measurement light that is emitted from the irradiator and reflected on the weld part so as to generate measured values; and a determiner configured to determine the weld penetration depth of the weld part based on (i) one or more measured values; or (ii) an average value of the one or more measured values, the one or more measured values being included within a predetermined range with reference to a greatest side measured value of the plurality of measured values.