Laser Weld Penetration Sensing for Overlap Gap Correction
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Solution Overview
Problem
Laser welding devices face challenges in accurately measuring the depth of penetration when welding overlapping workpieces, particularly due to gaps between them, leading to incorrect measurements and potential melt-through issues.
Innovation Solution
The device emits a laser beam and a measurement beam with a different wavelength, allowing the irradiation position of the measurement beam to be switched between the keyhole position and the weld bead position or boundary position, enabling accurate measurement of the keyhole depth and gap detection, with correction and adjustment of welding conditions to prevent insufficient penetration and melt-through.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the measurement beam is emitted coaxially with the laser beam to measure keyhole depth, then the depth of penetration can be measured, but the measurement value becomes incorrect when there is a gap between overlapping workpieces
Solution Approach 1:
The measurement process is segmented into two distinct parts: (1) measuring the keyhole depth at the irradiation position using the measurement beam, and (2) separately measuring the gap between workpieces at a different position. By dividing the measurement into these segments, the patent avoids the error that occurs when attempting to measure both simultaneously at the same position, thereby resolving the contradiction between measurement precision and reliability.
Solution Approach 2:
The patent introduces an intermediary measurement approach by using the measurement beam to first detect the gap between workpieces, and then using this gap information as a correction factor for the keyhole depth measurement. This intermediary step allows the system to account for gap effects without directly measuring at the problematic coaxial position, thus improving measurement reliability while maintaining precision.
2Strength
If the laser output is increased to ensure sufficient depth of penetration, then the bonding strength improves, but melt-through may occur when there is a gap between workpieces
Solution Approach 1:
The system performs preliminary measurement of the gap between workpieces before executing the welding operation. Based on this advance information about the gap, the laser output is pre-adjusted to an appropriate level that ensures sufficient penetration without causing melt-through. This preliminary action allows the system to optimize welding parameters in advance, resolving the contradiction between achieving sufficient bonding strength and preventing harmful melt-through.
Solution Approach 2:
The patent implements a feedback mechanism where the measured gap information is fed back to the control system, which then adjusts the laser output accordingly. This closed-loop control ensures that the laser power is optimized based on actual workpiece conditions, allowing sufficient penetration for strong bonding while preventing excessive energy input that would cause melt-through, thus resolving the strength-harmful factors contradiction.
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 configuration ensures accurate measurement of keyhole depth and gap detection, preventing melt-through and ensuring sufficient bonding strength by adjusting welding conditions based on gap measurements.
Implementation Method 1
a measurement unit configured to measure a depth from a predetermined reference surface based on the measurement beam emitted by the irradiation unit and reflected from the workpieces
Implementation Method 2
an irradiation unit configured to emit, to the workpieces, a laser beam and a measurement beam
Data Source
AI summary
A laser welding device is configured to switch an irradiation position of a measurement beam between a position of a keyhole coaxial with the optical axis of a laser beam and a position of a weld bead behind the center of an optical axis of the laser beam in a welding direction. The laser welding device determines whether there is a gap between an upper metal plate and a lower metal plate based on a measured value of a recess depth measured at the position of the weld bead.