Laser Welding Focal Deviation Compensation via Inspecting Beam
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Solution Overview
Problem
Conventional laser welding methods fail to properly adjust the focal length of the laser beam when spatters adhere to the protective glass of a laser processing device, leading to poor welding due to the thermal lens effect, as existing detection methods cannot accurately measure the resulting focal deviation.
Innovation Solution
A laser welding method that includes a decrease-amount calculating step and a focal-deviation-amount calculating step, where an inspecting laser beam with lower power is used to detect the intensity change and calculate the power decrease and focal deviation, allowing for adjustments to the laser oscillator's output and focal length to prevent reduced laser beam power and improve welding quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spatters adhere to the protective glass, then the protective glass blocks part of the laser beam, but the existing detection method cannot measure the focal length variation caused by thermal lens effect
Solution Approach 1:
The patent introduces an intermediary inspecting laser beam with a different wavelength than the welding laser beam. This intermediary beam serves as a probe to detect the optical properties of the protective glass and measure focal length variations without being affected by the thermal lens effect generated during actual welding. The intermediary measurement system indirectly captures the focal length information that would otherwise be lost.
Solution Approach 2:
The patent replaces direct mechanical measurement of focal length with an optical measurement system. Instead of physically measuring the focal point position, the system uses an optical receiver to detect the intensity distribution of the inspecting laser beam after it passes through the protective glass, thereby optically inferring the focal length variation caused by thermal lens effect.
2Reliability
If the focal length varies due to thermal lens effect, then welding quality deteriorates, but the conventional method cannot detect or adjust for this focal deviation
Solution Approach 1:
The patent performs preliminary measurement of the inspecting laser beam intensity distribution before actual welding occurs. By measuring the optical properties of the protective glass and calculating the focal length variation in advance, the system can predict and compensate for the thermal lens effect before it degrades welding quality. This preliminary action allows proactive adjustment of welding parameters.
Solution Approach 2:
The patent establishes a feedback loop where the optical receiver continuously monitors the intensity distribution of the inspecting laser beam, the controller calculates the focal length variation based on this data, and the system adjusts welding parameters accordingly. This closed-loop feedback mechanism enables real-time compensation for thermal lens effect, maintaining welding quality despite focal length variations.
3Power
If the laser beam power is reduced due to spatter adhesion, then welding effectiveness decreases, but the system lacks the capability to adjust output accordingly
Solution Approach 1:
The patent implements a feedback control system where the optical receiver measures the intensity of the inspecting laser beam after it passes through the protective glass, the controller calculates the power reduction based on this measurement, and the laser oscillator output is automatically adjusted to compensate. This feedback mechanism maintains effective welding power despite spatter adhesion and thermal lens effect.
Solution Approach 2:
The patent dynamically changes the output power parameter of the laser oscillator based on real-time measurements. By adjusting the laser beam power parameter in response to detected spatter adhesion and focal length variation, the system maintains optimal welding conditions despite changing environmental factors.
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 method effectively detects dirt on the protective glass, measures focal deviation caused by the thermal lens effect, and adjusts the focal length, preventing poor welding by ensuring the laser beam's power is maintained, thus reliably improving the quality of laser welding.
Implementation Method 1
the focal length of the laser beam varies due to 'thermal lens effect'. The 'thermal lens effect' is a phenomenon in which the laser beam is absorbed by the spatters adhering to the protective glass, and the refractive index of the protective glass varies in the parts around the spatters.
Implementation Method 2
an optical receiver which receives a return beam incident into the optical system out of the laser beam reflected on the welding portion
Data Source
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AI summary
Provided is a laser welding method capable of easily restraining poor welding when spatters adhere to a protective glass of an optical system. The laser welding method includes a decrease-amount calculating step performed before laser welding is performed by irradiating a welding portion of a workpiece with the laser beam having a predetermined power. The decrease-amount calculating step includes irradiating the welding portion with an inspecting laser beam having a power smaller than the predetermined power, receiving a return beam of the inspecting laser beam, measuring the intensity of the return beam, and comparing the intensity of the return beam with a standard intensity to calculate an amount of decrease in power of the inspecting laser beam at the welding portion. The invention refers also to a laser processing device (100) comprising a laser oscillator (10), an optical system (20), a protective glass (20), a controller (40), used in performing said method.