Laser Welding Penetration Measurement Under Optical Axis Deviation
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Solution Overview
Problem
Laser welding methods face inaccuracies in measuring the penetration depth of weld portions 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 coaxially aligning a laser beam and a measurement beam with different wavelengths, moving their irradiation positions in various directions during welding, determining the optical axis deviation direction, and applying a correction value to ensure accurate penetration depth measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a beam splitter is used to separate the laser beam and measurement beam, then the measurement can be performed, but the beam splitter may warp due to heat causing misalignment of optical axes
Solution Approach 1:
The patent introduces a reference mark as an intermediary element that serves as a stable reference for both the laser beam and measurement beam. By aligning both beams to the same reference mark, the system compensates for beam splitter warping, as the reference mark provides a common reference frame that remains stable despite thermal effects on the beam splitter.
Solution Approach 2:
The patent changes the measurement approach by measuring penetration depth at multiple positions (front, center, rear) of the keyhole bottom rather than relying on a single central measurement. This parameter change allows the system to detect and compensate for optical axis deviations caused by beam splitter warping, as the distribution of measurements across multiple positions reveals the alignment errors.
2Device complexity
If the measurement beam is coaxially aligned with the laser beam, then the measurement setup is simplified, but heat-induced warping causes the measurement beam to deviate and measure shallower penetration
Solution Approach 1:
The patent performs preliminary alignment of both the laser beam and measurement beam to a reference mark before welding begins. This preliminary action establishes a stable reference frame that accounts for potential beam splitter warping, allowing the system to maintain measurement accuracy despite the simplified coaxial alignment approach.
Solution Approach 2:
The patent implements a feedback mechanism where penetration depth is measured at multiple positions (front, center, rear) and these measurements are used to determine and correct for optical axis deviation. The system uses the measured values to identify the direction and magnitude of deviation, then applies correction to achieve accurate penetration depth measurement.
3Measurement precision
If multiple measurements are taken in different directions, then optical axis deviation can be detected, but the measurement process becomes more complex
Solution Approach 1:
The patent measures penetration depth at three specific positions (front, center, rear) of the keyhole bottom, which is more than a single measurement but less than exhaustive mapping. This partial measurement approach provides sufficient information to detect and correct optical axis deviation without requiring overly complex measurement procedures, achieving a balance between accuracy and simplicity.
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 accurate determination of the penetration depth, even when optical axis misalignment occurs, by identifying and correcting for deviations in the measurement beam's alignment.
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
The laser welding device is configured to coaxially align a laser beam with a measurement beam and emit the coaxially aligned beams into a keyhole of a weld portion
Data Source
AI summary
Laser welding is performed while moving irradiation positions of a laser beam and a measurement beam in forward, rightward, rearward and leftward directions, and the penetration depth of a weld portion 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.