Laser Welding Head With Overlapping Spots for Crack Prevention
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Solution Overview
Problem
High-silicon steel plates used in transformer and motor laminations often suffer from welding defects such as cracking, especially when the silicon content exceeds 4.3wt%, and conventional welding techniques at room temperature lead to deformation and cracking in low-temperature conditions.
Innovation Solution
A laser welding head utilizing a collimation lens, a condensing lens, and a hollowed convex or concave cylindrical lens to form a high power density spot and a lower power density spot, which overlap on the welding plane, preventing cracking and enhancing welding quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional welding techniques are used at room temperature for high-silicon steel plates, then welding process simplicity is maintained, but welding quality deteriorates due to cracking and deformation
Solution Approach 1:
The laser beam is segmented into multiple beams through the use of a beam splitting optical system, creating multiple focal points that can be distributed across the welding area. This segmentation allows the welding process to address cracking and deformation issues by distributing thermal input across multiple zones rather than concentrating it in a single location.
Solution Approach 2:
The patent employs parameter changes by adjusting laser beam parameters (number of beams, focal point distribution, power density) and optical system parameters (lens focal lengths, beam spacing) to optimize welding quality for high-silicon steel plates without requiring preheating or post-heating processes.
2Reliability
If preheating or post-heating is implemented to prevent cracking, then welding quality improves, but thermal distortion increases and dimensional accuracy deteriorates
Solution Approach 1:
The patent implements preliminary action by using the distributed focal points to pre-distribute thermal energy across the welding zone before complete fusion occurs. This preliminary thermal distribution prevents stress concentration that leads to cracking, while avoiding the excessive thermal input of traditional preheating that causes distortion.
Solution Approach 2:
The patent replaces the mechanical/thermal system of conventional preheating and post-heating with an optical system that uses laser beam distribution and focal point control to achieve crack prevention without the thermal distortion associated with traditional heating methods.
3Productivity
If a single high power density spot is used for welding, then welding speed is improved, but welding quality deteriorates due to concentrated thermal stress causing cracking
Solution Approach 1:
The single high power density spot is segmented into multiple focal points that are distributed across the welding area. This segmentation maintains high welding speed by keeping total power density high while distributing the thermal stress across multiple locations, preventing the concentrated stress that causes cracking in single-spot welding.
Solution Approach 2:
The patent applies local quality by creating different power density zones through distributed focal points - high power density at each focal point for efficient welding, but distributed across multiple locations to prevent stress concentration. This local variation in power density distribution achieves both speed and quality.
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
The solution prevents welding cracking, enhances the quality and yield of the welding process, and allows for flexible adjustment of the power ratio between the high and lower power density spots, accommodating various materials and shapes.
Implementation Method 1
remaining light beams that transmit through a curved portion of the cylindrical lens changes a beam angle thereof in transmission through the optical axis in individual direction due to the curved surface of the cylindrical lens
Implementation Method 2
uses a collimation lens and a condensing lens to form an image with laser light emerging from an optical fiber
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 2(c)
AI summary
A laser apparatus includes a single-core optical fiber (2) and a barrel (3) for converging of emergent light from the single-core optical fiber (2) in order to realize combined welding of a high power density spot and/or a lower power density spot. In an interior of the barrel, a cylindrical lens (10), a collimation lens (12), and a condensing lens (13) are sequentially arranged on a same optical axis as the single-core optical fiber. The cylindrical lens (12) is arranged in the interior of the barrel and located between an output of the optical fiber and the collimation lens. (12) The cylindrical lens (10) has a focal distance that is longer than that of the condensing lens (13). A hollowed portion of the cylindrical lens (10) is arranged in a light beam emerging from the optical fiber. The present invention possesses advantages of being flexibly corresponding to fiber lasers of all manufacturers and being also capable of single mode transmission, and being capable of realizing combined welding of keyhole type and heat conduction type by using a simple single-core optical fiber with high durability.