Transparent Workpiece Laser Welding with Energy Modulation
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Solution Overview
Problem
Existing welding methods using focused laser beams for transparent and non-transparent workpieces face challenges due to high local energy input, leading to temperature stresses, tensions, and potential cracking in the weld seam.
Innovation Solution
Modulating the energy connected to the process zone by the laser beam reduces temperature stresses and allows for more homogeneous energy distribution, enabling larger and more complex modifications without cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a focused laser beam is used to weld transparent workpieces, then welding speed and energy efficiency are improved, but thermal stresses and cracking in the material increase
Solution Approach 1:
The patent applies periodic modulation of the laser beam energy at frequencies between 100 Hz and 10 kHz to create cyclic heating and cooling cycles. This periodic action prevents continuous thermal accumulation, reduces peak temperatures, and minimizes thermal stresses that cause cracking, while maintaining effective welding through sustained energy input over time.
Solution Approach 2:
The patent dynamically adjusts laser beam parameters including energy modulation depth (10-90%), frequency (100 Hz-10 kHz), and pulse duration (10 ns-10 µs) to optimize the balance between welding efficiency and stress reduction. This dynamic control allows real-time adaptation to material conditions and welding progress.
2Productivity
If high energy density is concentrated in the process zone, then welding efficiency is improved, but the risk of material damage and cracks increases
Solution Approach 1:
By modulating the laser energy periodically, the patent creates cycles of high energy concentration followed by cooling periods. This allows the material to dissipate heat between pulses, preventing thermal runaway and material damage, while still achieving effective welding through cumulative energy input during the high-energy phases.
Solution Approach 2:
The patent changes multiple laser parameters simultaneously including energy density, pulse duration, repetition frequency, and modulation depth to optimize the energy input profile. This multi-parameter optimization ensures sufficient energy for welding while preventing excessive thermal accumulation that would compromise material integrity.
3Speed
If continuous laser energy input is used, then processing speed is improved, but heat accumulation and thermal stresses increase
Solution Approach 1:
The patent replaces continuous energy input with periodic pulsed energy input, where the duty cycle (10-90%) and frequency (100 Hz-10 kHz) are optimized to maintain average power for processing speed while allowing periodic cooling to prevent heat accumulation. This achieves both fast processing and temperature control.
Solution Approach 2:
The patent applies preliminary cooling periods between laser pulses, allowing heat to dissipate before the next energy input. This preliminary action prevents thermal buildup while maintaining overall processing efficiency through optimized pulse timing and duration.
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 approach reduces transient and permanent tensions in the material, allows for improved processing efficiency, and enables the creation of larger, crack-free welds and modifications.
Implementation Method 1
generate a melt by energy absorption in the process zone exposed to the laser beam
Implementation Method 2
focusing the processing laser beam into the process zone such that the energy input is highest in the process zone area
Implementation Method 3
By temporally modulating the energy injected into the process zone by the laser beam, the thermal stresses generated in the material can be reduced
Data Source
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AI summary
The invention relates to a method for processing at least one workpiece, preferably for welding two workpieces, having the step of supplying a processing zone of the at least one workpiece with a pulsed laser beam, preferably an ultrashort pulse laser beam, wherein the energy coupled into the processing zone by the laser beam (110) is modulated over time.