Laser Welding Keyhole Depth Measurement Stability
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Solution Overview
Problem
The penetration depth of a keyhole in laser welding cannot be stably measured due to variations in welding conditions, such as the formation of a penetration bead and changes in the keyhole shape caused by molten metal vaporization, leading to inconsistent measurement values.
Innovation Solution
A method involving emitting a measurement beam to the keyhole during laser welding, dividing measured values into regions, counting the number of points over time, and calculating the average variation to determine if the measurement is stable, with additional steps to identify gaps between workpiece members if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser welding is performed under high temperature conditions causing molten metal vaporization, then welding penetration depth increases, but keyhole shape becomes unstable and measurement precision deteriorates
Solution Approach 1:
The patent applies dynamics by continuously monitoring the keyhole shape over time and detecting temporal changes. The system captures multiple images of the keyhole during welding and analyzes the variation in shape, allowing it to adapt to the dynamic nature of the keyhole while maintaining measurement accuracy despite the unstable conditions caused by high temperature vaporization.
Solution Approach 2:
The patent implements feedback by using the detected keyhole shape variations to evaluate welding quality. The system provides real-time feedback on whether the welding conditions are appropriate by analyzing the stability of keyhole shape measurements, enabling adjustment of welding parameters to maintain optimal measurement and welding conditions.
2Strength
If penetration bead formation is used as an indicator of welding quality, then welding strength improves, but measurement stability deteriorates due to random bead formation
Solution Approach 1:
The patent replaces the mechanical/visual assessment of penetration beads with an optical measurement system. Instead of relying on post-weld inspection of bead formation, the system uses optical imaging to directly measure keyhole shape and penetration depth during welding, providing more reliable and stable measurements that are not affected by the random nature of penetration bead formation.
Solution Approach 2:
The patent performs preliminary measurement of the keyhole shape during the welding process itself, before the weld is completed and cooled. This allows for real-time assessment of welding quality based on keyhole characteristics rather than relying on post-weld inspection of penetration beads, enabling earlier detection and correction of welding issues.
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
Enables determination of whether the welding condition is suitable for stable measurement of the keyhole penetration depth by evaluating the average variation in point data, ensuring accurate assessment of welding quality.
Implementation Method 1
a first step of emitting a measurement beam to a keyhole of the workpiece during the laser welding to measure a penetration depth of the keyhole
Data Source
AI summary
Point group data obtained by measuring the penetration depth of a keyhole 66 during laser welding is divided into a plurality of regions in the depth direction of measured values, and evaluation data showing a change in number of points with time is acquired for each of the plurality of regions. An average variation in number of points is calculated for each of the plurality of regions based on the plurality of pieces of evaluation data. When the average variation is equal to or larger than a predetermined threshold, it is determined that measurement of the penetration depth of the keyhole 66 is unstable under the welding condition.