Laser Weld Monitoring for Transparent Workpiece Gap Bridging
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Solution Overview
Problem
Current methods for monitoring laser welding of transparent workpieces, such as glass, require time-consuming manual inspections to assess the quality of welds and determine if gaps are bridged, which is inefficient and lacks real-time feedback.
Innovation Solution
Evaluating the intensity profile of the process radiation emitted during laser welding, specifically the depth and duration of intensity drops and increases, to determine if a gap is bridged, allowing for real-time assessment of weld quality and gap position and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual inspection methods are used to assess weld quality and detect gaps, then measurement precision can be achieved, but productivity is significantly reduced due to time-consuming post-welding examination
Solution Approach 1:
The patent applies preliminary action by performing quality monitoring during the welding process itself rather than after completion. The photodetector continuously monitors process radiation intensity throughout welding, enabling real-time detection of gap bridging events before the weld is finished, thus eliminating the need for separate post-welding inspection steps
Solution Approach 2:
The patent replaces manual mechanical inspection methods with an optical detection system. Instead of using microscopes and manual examination, the system uses photodetectors to monitor process radiation intensity, automatically detecting gap bridging through optical signal analysis, thereby substituting mechanical inspection with optical sensing
2Productivity
If real-time monitoring of the welding process is implemented, then productivity is improved through continuous processing, but device complexity increases due to additional sensing and evaluation systems
Solution Approach 1:
The patent applies universality by making the process radiation detection system serve multiple functions. The same photodetector and intensity monitoring system that monitors welding progress also detects gap bridging events, enabling both process control and quality assessment with a single integrated system rather than separate dedicated devices
Solution Approach 2:
The patent applies self-service by using the welding process's own process radiation as the monitoring signal source. The melt volume naturally emits process radiation during welding, and this self-emitted radiation is captured by the photodetector, eliminating the need for external illumination or separate sensing sources that would increase system complexity
3Measurement precision
If the position and size of gaps are determined microscopically after welding, then measurement precision is achieved, but loss of time occurs due to post-process examination
Solution Approach 1:
The patent performs gap detection during the welding process itself by monitoring process radiation intensity changes that occur when melt bridges the gap. This preliminary detection provides real-time information about gap position and bridging status before the weld is completed, eliminating the need for time-consuming post-welding microscopic examination
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 direct, real-time quality inspection of welded joints during processing, eliminating the need for manual inspections and improving the efficiency of the welding process by accurately determining if a cohesive connection has been made.
Implementation Method 1
a melt volume in the region of the interface between the two workpieces is melted by a pulsed laser beam, in particular an ultrashort pulse laser beam
Implementation Method 2
absorption is drawn in the direction of the incident wavefront over several pulses, as this is where preferential absorption occurs due to the elevated temperature
Implementation Method 3
the intensity of the process radiation emitted by the melt volume is detected
Data Source
Figure 1
Figure 2a~2f
AI summary
The invention relates to a method for monitoring a laser welding process for welding two workpieces (2, 3) which are transparent to the laser wavelength, preferably workpieces made of glass, wherein a melt volume (7) is melted in the workpieces (1, 2) by a pulsed laser beam (4), in particular an ultrashort pulse laser beam, in the region of the boundary surface (5) of the two workpieces (2, 3) in order to produce a welding seam (8), wherein the intensity of the process radiation (10) emitted from the melt volume (7) is detected. According to the invention, the detected intensity curve is analyzed with respect to at least one of the following features: - the extent (ΔI) of an intensity decrease, - the duration (Δt) of an intensity decrease, and - the renewed increase (17) of the intensity after an intensity decrease, and the analysis is used to determine whether the gap (9) has been bridged or not during the laser welding process.