Laser Welding Plastic Members Modulated Focus Seam Depth
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Solution Overview
Problem
Conventional laser welding of plastics faces challenges in controlling the shape and quality of the weld seam, particularly in the z-direction, due to limitations in thermal energy distribution and surface damage risks.
Innovation Solution
Modulating the laser power density in the z-direction by adjusting the focus position and feed speed, allowing the laser beam to sweep over the seam depth, thereby optimizing energy input and seam geometry, and using a device with adjustable lenses or a 3D scanner for precise focal position control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the laser beam is radiated through the surface of joining partners into the welding zone, then the welding zone can be heated to form a weld seam, but the surface can be affected by thermal effects and the weld seam strength and quality may be insufficient
Solution Approach 1:
The patent applies dynamic modulation of the laser focus position in the z-direction (perpendicular to the welding plane) during the welding process. The focus position is continuously varied according to a modulation function, causing the laser beam to dynamically sweep through different depths within the workpiece. This dynamic focusing strategy concentrates thermal energy within the interior welding zone while minimizing surface exposure to excessive heat, thereby improving weld seam strength without causing surface thermal damage.
Solution Approach 2:
The patent implements periodic modulation of the laser focus position through a sinusoidal or triangular modulation function. The focus position oscillates periodically between predetermined limits in the z-direction, creating a periodic sweeping motion that distributes thermal energy uniformly throughout the weld depth. This periodic action ensures thorough heating of the welding zone while preventing localized surface overheating, thus resolving the contradiction between weld strength and surface damage prevention.
2Manufacturing precision
If the focus position is modulated to sweep over the seam depth, then the seam geometry and energy input are optimized, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical positioning systems with a computational approach. Instead of using multiple movable components to physically reposition the laser beam through the workpiece depth, the invention uses a modulation function controlled by a computer or control unit to vary the focus position. This substitution of mechanical complexity with electronic/software control achieves precise seam geometry control while minimizing device complexity.
Solution Approach 2:
The patent achieves precise control of seam geometry by dynamically changing the focal parameter (focus position in z-direction) during the welding process. The modulation function varies the focus position according to a predetermined pattern, effectively controlling the energy distribution and melt pool formation. This parameter modulation approach provides precise manufacturing control through software-based parameter variation rather than complex mechanical adjustments.
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 enhances the seam depth and quality, ensuring a strong and evenly distributed weld while maintaining sufficient distance from the surface edges to prevent damage, resulting in improved joint strength and consistency.
Implementation Method 1
Conventional plastic laser welding processes are based on the introduction of thermal energy into the welding zone by means of the focused laser beam
Implementation Method 2
The latter melts, thermal energy is transferred to the transmissive joining partner, which also melts
Implementation Method 3
a focused laser beam is radiated into a welding zone
Implementation Method 4
the laser power density is modulated in the direction of the seam depth in the welding zone. The modulation takes place by modulating the focus position of the laser beam
Data Source
Figure 1
Figure 2a~2c
Figure 3a~3c
AI summary
In a method and device for laser welding of two plastic members to be joined, in which a focused laser beam (1) is irradiated into a welding zone (S) in the area of the boundary surfaces (4, 5) facing one another of the members to be joined (2, 3) in order to form a weld seam (7) with a defined seam depth (T) between the members to be joined (2, 3), it is provided that the laser power density in the direction (z) of the seam depth (T) in the welding zone (S) is modulated during the welding process.