Laser Welding Scan Pattern for Hairpin Pin Spatter Control
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Solution Overview
Problem
Laser welding of metal pin pairs, particularly hairpins and I-pins in stators, faces issues with spatter and void formation in keyhole welding, which reduce the volume and conductivity of the weld nugget, impacting the performance of rectangular bar wire stators.
Innovation Solution
A method involving a time-dependent laser scan pattern and energy input, where a first path is traced with a higher energy rate to form a melt pool, followed by a second path with a reduced energy rate, minimizing spatter and maximizing the depth and area of the weld nugget along the interface between the metal pins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If keyhole welding is used to achieve deep penetration and strong welds, then weld depth and strength are improved, but spatter and void formation increase
Solution Approach 1:
The patent applies periodic action by using a pulsed laser beam with varying power levels during welding. The laser operates in cycles of high power (to maintain keyhole and achieve deep penetration) and low power (to allow molten metal to calm and reduce spatter). This periodic modulation of laser power resolves the contradiction between achieving deep strong welds and minimizing spatter and voids.
Solution Approach 2:
The patent employs dynamics by continuously adjusting laser power, pulse duration, and scanning speed during the welding process. The laser parameters are dynamically modified based on real-time conditions to maintain optimal keyhole stability, controlling metal vaporization rates, and managing melt pool behavior. This dynamic control allows the system to achieve deep penetration while minimizing harmful spatter and void formation.
2Length of moving object
If high laser power density is used to create keyhole welding, then weld penetration depth is improved, but metal evaporation and spatter increase
Solution Approach 1:
The pulsed laser delivers power in periodic cycles with high peak power followed by lower power intervals. During high power phases, the laser creates and maintains the keyhole for deep penetration. During lower power phases, metal vaporization is reduced, allowing evaporated material to condense and return to the melt pool, thereby reducing spatter and material loss while maintaining weld depth.
Solution Approach 2:
The patent changes multiple laser parameters including power level, pulse duration, duty cycle, and scanning speed to optimize the welding process. By adjusting these parameters, the system achieves sufficient keyhole penetration depth while controlling the intensity and duration of metal vaporization, thereby minimizing spatter and material loss.
3Volume of moving object
If continuous high energy input is used to maximize weld nugget volume, then weld volume is improved, but spatter and process instability increase
Solution Approach 1:
The pulsed laser delivers energy in controlled periodic cycles rather than continuous input. The high power pulses create and maintain the keyhole and generate molten metal, while the lower power intervals between pulses allow the melt pool to stabilize, reduce spatter, and prevent excessive vaporization. This periodic energy delivery maintains weld nugget volume while significantly improving process stability and reducing spatter.
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 effectively reduces spatter and void formation, enhancing the electrical conductivity and depth of the weld nugget, thereby improving the performance of the welds in stators.
Implementation Method 1
Laser welding uses a continuous or pulsed laser beam as a concentrated heat source to locally melt and join two parts
Implementation Method 2
Keyhole welding occurs at higher laser powers and higher laser power densities that are sufficient to vaporize some of the irradiated material. Pressure of the vaporized material on surrounding melted material opens a channel through the melted material. This channel, known in the art as a keyhole, has a characteristic narrow and deep profile, which allows deep penetration of the laser beam
Implementation Method 3
Absorbed laser power heats the irradiated material, thereby melting material in each part to be joined, which flows, mixes, and then solidifies
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
A method for laser welding a pair of metal pins (182,200) delivers a laser beam (112) to a work-side (220) of the pair of metal pins (182,200) where a respective pair of surfaces (204) of the metal pins (182,200) are adjacent to each other and face in the same direction. The laser beam (112) first traces a first path (230,630) on the work-side (220) to form a melt pool (850)by keyhole welding. The first path (230,630) crosses an interface (210) between the metal pins (182,200). After tracing the first path (230,630), the laser beam (112) is switched to trace a second path (240,640) on the work-side (220) with the laser beam (112) at a delivered rate of energy per unit path length that is less than the one used for the first path (230,630). The second path (240,640) crosses the interface (210) and is within the first path (230,630). The method is well-suited for welding of hairpin and I-pin stators.