Laser Weld Penetration Measurement Using Filtered Interferometer Readings
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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 inaccurate results.
Innovation Solution
A laser welding device that measures weld penetration depth multiple times and determines the depth based on average values within a predetermined range, with the irradiation position of the measurement light moved on a predetermined welding path to ensure accurate alignment and reduce the impact of optical axis misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If measurement light is used to directly measure keyhole depth, then measurement capability is provided, but measurement accuracy deteriorates due to diffused reflection and external disturbances
Solution Approach 1:
The system continuously measures keyhole depth multiple times and uses feedback control to determine the final measurement. By comparing multiple measured values and selecting those within a predetermined range of the deepest value, the system eliminates erroneous shallow measurements caused by diffused reflection or external disturbances, thereby improving both accuracy and reliability
Solution Approach 2:
The system performs preliminary measurements multiple times before final determination. By pre-measuring the keyhole depth several times and identifying the deepest value as a reference, the system prepares a reliable baseline that filters out transient measurement errors, ensuring accurate final measurement results
2Measurement precision
If measurement is performed at a fixed position, then measurement simplicity is maintained, but measurement accuracy deteriorates due to optical axis misalignment
Solution Approach 1:
The system dynamically changes the irradiation position of the measurement light along the welding path and varies the optical axis position within a small radius. This dynamic measurement approach ensures that the measurement light captures the deepest keyhole position even when optical axis misalignment occurs, improving measurement accuracy without requiring complex realignment mechanisms
Solution Approach 2:
The system adds positional variation in the measurement process by moving the irradiation position along the welding path and adjusting the optical axis within a radius smaller than half the laser spot diameter. This dimensional approach to measurement ensures comprehensive coverage of the keyhole depth, eliminating the need for precise static alignment
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 precise measurement of the actual weld penetration depth, reducing variations and ensuring accurate assessment of the weld quality.
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 laser welding device for welding a weld part with laser light
Implementation Method 3
irradiate the inside of a keyhole of a weld part
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 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), thereby generating a plurality of measured values; and a determiner (17) determining the weld penetration depth of the weld part (35) based on (i) one or more measured values, where among the plurality of measured values, or on (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.