Laser Weld Penetration Measurement Under Optical Axis Deviation
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Solution Overview
Problem
Laser welding devices face inaccuracies in measuring keyhole penetration depth due to potential misalignment of optical axes caused by beam splitter warping, leading to shallower measurements when the measurement beam deviates from the laser beam.
Innovation Solution
The method involves moving the irradiation positions of both the laser and measurement beams in multiple directions during welding, comparing penetration depth values to determine optical axis deviation, and applying correction values to ensure accurate measurement of keyhole depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a beam splitter is used to separate the laser beam and measurement beam, then the measurement system can be configured, but the beam splitter may warp due to heat causing misalignment of optical axes
Solution Approach 1:
An alignment mark is introduced as an intermediary element that both the laser beam and measurement beam target. This common reference point allows the system to detect and compensate for optical axis misalignment caused by beam splitter warping, maintaining measurement precision while preserving the beam splitter-based configuration.
Solution Approach 2:
The patent replaces mechanical alignment adjustment with an optical field-based alignment method using alignment marks and image processing. Instead of mechanically adjusting the beam splitter position, the system uses digital image analysis to detect misalignment and calculate correction values, eliminating the need for mechanical intervention.
2Device complexity
If the measurement beam optical axis deviates from the laser beam, then the measurement system is simpler to configure, but the penetration depth measurement becomes inaccurate
Solution Approach 1:
The system performs preliminary alignment by capturing images of alignment marks with both the laser beam and measurement beam before actual welding begins. This preliminary action establishes the optical axis relationship and calculates correction values in advance, allowing the measurement system to remain simple while ensuring accurate penetration depth measurement during welding.
Solution Approach 2:
The system uses feedback from alignment mark images to detect optical axis deviation and automatically calculates correction values. This feedback mechanism allows the system to maintain simple configuration while compensating for misalignment, ensuring accurate measurements without complex mechanical adjustment systems.
3Measurement precision
If multiple penetration depth measurements are taken in different directions, then optical axis deviation can be detected, but the measurement process becomes more time-consuming
Solution Approach 1:
The system performs measurements in multiple directions (excessive action) to ensure accurate detection of optical axis deviation, but only applies corrections during actual welding operations. The preliminary multi-directional measurement phase is kept separate from the production welding phase, so the time investment is made once rather than repeatedly, minimizing overall time loss.
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 reduces variations in measured values and allows for precise determination of keyhole penetration depth, even when optical axis misalignment occurs, thereby improving the accuracy of weld quality assessment.
Implementation Method 1
The measurement beam is reflected from the bottom of the keyhole and received by an optical interferometer via a beam splitter. Since the optical interferometer can measure the optical path length of the measurement beam, the depth of the keyhole is detected from the measured optical path length
Implementation Method 2
emitting, to the weld portion, the laser beam and a measurement beam coaxially aligned with the laser beam
Implementation Method 3
performing laser welding while moving an irradiation position of the laser beam
Data Source
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AI summary
Laser welding is performed while moving irradiation positions of a laser beam L and a measurement beam S in forward, rightward, rearward and leftward directions, and the penetration depth of a weld portion 35 is measured during laser welding in each of the directions. Then, a direction in which a value smaller than a reference value is measured is determined to be an optical axis deviation direction, and a correction value is added to the values measured during the laser welding when the laser welding is performed in the optical axis deviation direction.