Laser Welding Monitoring via Reflected Beam Start Detection
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Solution Overview
Problem
Existing laser welding monitoring devices struggle to accurately detect the start of welding by a laser welding machine, as some laser oscillators do not output a signal indicating the start of laser beam emission.
Innovation Solution
A laser welding monitoring device and method that utilize a beam receiving unit to capture both the reflected laser beam and a monitoring beam caused by thermal radiation, with a spectrometer unit to separate and convert these beams into electric signals, and a trigger unit to generate a trigger signal when the reflected beam's signal level reaches a threshold, initiating monitoring to determine if welding is performed normally.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the monitoring device waits for a signal from the laser oscillator to start monitoring, then the device can start monitoring, but some laser oscillators do not output such a signal causing monitoring to fail to start
Solution Approach 1:
The patent uses the reflected laser beam as an intermediary signal to detect the start of welding. Instead of relying on the laser oscillator's output signal (which may not be available), the system detects the reflected beam from the workpiece, which reliably indicates when the laser actually reaches the material. This intermediary approach resolves the contradiction by providing a reliable monitoring start trigger without adding complex signal detection systems.
2Loss of time
If the monitoring device starts monitoring immediately when the laser oscillator emits the beam, then monitoring timing is accurate, but the device cannot detect the actual welding start if no signal is provided
Solution Approach 1:
The patent replaces the electrical signal-based detection system with an optical detection system. By using a photodetector to measure the intensity of the reflected laser beam from the workpiece, the system directly detects the physical presence of the laser at the welding location. This substitution eliminates monitoring delay while maintaining accurate welding start detection, as the optical signal provides direct evidence of laser-material interaction.
3Measurement precision
If the system uses the reflected beam to trigger monitoring, then monitoring starts accurately, but the system must differentiate between reflected beam and thermal radiation signals
Solution Approach 1:
The patent utilizes the temporal parameter difference between the reflected beam and thermal radiation signals. The reflected beam appears immediately when the laser starts, while thermal radiation develops gradually as the material heats up. By setting a threshold on the reflected beam intensity and using it as a trigger, the system achieves precise welding start detection without complex signal separation, as the reflected beam's immediate appearance provides a clear temporal marker.
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 accurate and timely detection of the welding start, allowing for immediate monitoring with minimal delay and high repeatability, ensuring reliable assessment of laser welding processes.
Implementation Method 1
a radiated beam generated at an irradiation position of the laser beam and including a reflected beam of the laser beam and a monitoring beam caused by thermal radiation
Implementation Method 2
a spectrometer unit configured to spectrally separate the reflected beam and the monitoring beam included in the radiated beam
Data Source
AI summary
When a material to be welded is irradiated with a laser beam emitted by a processing head, a beam receiving units receive a radiated beam including a reflected beam of the laser beam and a monitoring beam that is caused by thermal radiation and is a beam having a wavelength different from that of the reflected beam. A spectrometer unit spectrally separates the reflected beam and the monitoring beam, and converts the monitoring beam into a first electric signal. A trigger unit converts the reflected beam into a second electric signal, and outputs a trigger signal when a level of the second electric signal is a predetermined threshold value or higher. When the trigger signal is input, a laser welding monitor starts, based on the first electric signal, a determination of whether or not laser welding of the material to be welded is normally performed.