Nowadays, the laser welding technique is quickly applied to production lines in all walks of life, with laser marking, engraving, cutting, and welding as the main application processes. In addition, laser repair and laser cleaning are also used in a small number of specific scenarios.
For a long time, laser welding is considered to have great market potential, but due to insufficient laser power, workpiece fixtures, and a high threshold for automatic control research and development, the market application has not been well developed.
In the past, most laser welding used traditional YAG lasers and CO2 lasers. The traditional laser welding stand-alone equipment, the technical threshold is not high. This low-power welding machine can only perform simple welding for specific industries such as molds, glasses, jewelry, and advertising channel letter making, and has a narrow application range.
Development of laser welding technique
Fiber laser welding continues to expand in terms of the materials and applications that can be welded. Innovations in laser technology and beam delivery devices are overcoming the application challenges that laser welding has faced, such as welding copper, dissimilar materials, thin metal foils, or poorly assembled parts.
Fiber lasers offer an increasing choice of beam characteristics, wavelengths, output powers, and pulse durations. Combined with advanced oscillation welding technology, fiber lasers have significantly alleviated past application challenges through advances in “improved coupling to highly reflective materials, improved solidification behavior of the melt pool, elimination of defects, improved penetration depth control, and compensation for poorly assembled parts”.
In addition, integrated full-process monitoring technologies, such as coherent imaging, allow a wealth of information to be collected in real-time during the welding process, helping manufacturers to tightly control weld quality and improve productivity. Together, these driving technologies are facilitating the rapid adoption of defect-free laser welding technology in advanced applications across a wide range of industries.
Standard welding heads are designed to focus a collimated laser beam to the desired spot size and keep the beam path static during beam delivery, presenting a static spot in the focal plane. This standard configuration results in each setup being limited to being geared toward a specific application. In contrast, the oscillating weld head incorporates scanning oscillator technology within the standard weld head. By moving the beam with an internal mirror, the focal spot is no longer static and can be dynamically adjusted by changing the shape, amplitude, and frequency of the various patterns. The beam speed Vc can be controlled by the oscillation frequency f and the oscillation diameter D, Vc = π D f.
The benefits of this oscillation welding method are more apparent when smaller spots are used. When using near-infrared (NIR) wavelengths, the smaller spot achieves a large power density, overcoming the high reflectivity of materials such as copper and aluminum, resulting in stable keyholes with a wide processing window and avoiding porosity and cracking when using optimal oscillation parameters. This opens up new applications for 1µm fiber lasers in electric vehicle and battery manufacturing, eliminating the need for frequency-doubled green lasers.
In the past two years, handheld laser welder has achieved good shipments, because the price of a set of laser welding equipment has dropped significantly, at least about 10,000 US dollars, while a set of traditional low-power argon arc welding is cheap at 500 US dollars, and expensive up to $2000.
In addition, the laser welding speed is fast, the welding surface effect is good, and the sealing performance is good, which has become the choice for many hardware processing. But hand-held laser welding still relies on manual labor, and there is no automation.
In the future, apart from a few extra-large parts, structural parts with high added value require customized welding, such as rail locomotives and aerospace parts, and most other mass-produced industries need automated laser welding production lines, such as batteries, communication devices, watches, consumer electronics components, etc.
Power batteries promote the development of laser welding technique
About 8 years ago, the world began to vigorously promote the development of new energy vehicles, mainly electric vehicles. On the one hand, it can reduce automobile exhaust pollution caused by oil use, and at the same time, it can promote the replacement of automobiles and promote the consumption economy.
Sales of new energy vehicles have grown significantly over the past five or six years, and many automakers have joined the ranks to launch electric cars. The country’s long-term goal is to make new energy vehicles account for nearly one-third of annual sales. Then the core technology of electric vehicles is of course batteries. The large demand for power batteries has led to the rise of a number of lithium battery companies.
Power batteries bring a lot of demand for laser processing. The manufacturing process needs to use laser cutting, and more laser welding is used. Connecting sheets, cells, copper materials, as well as aluminum alloys, battery packaging, etc., are all laser welding. The laser equipment for power batteries is a highly automated production line workstation with certain thresholds. Power batteries have brought new breakthroughs to the demand for laser welding, driving more than 2.5 billion in demand for welding equipment in 2020.
Electric vehicles in particular are the main driver of this trend, and the automotive industry and automotive suppliers are looking for robust, efficient welding processes for the high-volume production of copper and aluminum joints, which are in wide demand in electric vehicles (EV) batteries and power storage products.
Another problem in copper welding is instability, as the low viscosity and surface tension of the molten metal can lead to spatter and porosity when welding at low speeds. Increasing the speed to over 10m/min minimizes these instabilities and creates a stable welding process. However, this means that the best welding parameters are within the limits reached by conventional motion systems, such as robots. In addition, the depth of melt decreases with increasing speed and the weld seam becomes very narrow. This has to be compensated by increasing the laser power, which requires a higher capital investment in the system.
New process studies show that the above phenomena can be avoided and that stabilization of the welding process can be achieved not only by increasing the welding speed, but also by dynamic positioning of the laser technology, e.g. with an oscillating welding head to achieve a stable weld. This oscillation technique allows stable welding at low linear welding speeds with minimal effect on the depth of melt. For example, high-quality copper welds up to 1.5 mm deep can be achieved with only one 1 kW single-mode fiber laser.
The same technology is available for high-brightness multimode lasers and has been used extensively to improve weld quality and weld consistency in aluminum housings. The gradient of temperature and cooling rate change is slower than conventional laser welding, which helps to eliminate defects and suppress spatter generation.
A comparison of welding 5000 series aluminum housings with standard welding technology and oscillating welding technology, using the same 3.0kW power, shows that oscillating welding results in a more consistent, porosity-free weld. With a weld depth of 5mm, it is clear that the oscillating welding technique is superior in terms of overall weld quality.
In conclusion
Power batteries are only one area of laser welding applications. In the future, we predict that there will be more industrial processes using laser welding techniques, and the process will be batched when process matures. Laser welding often requires reliable parts and stability of welding quality. Varibend has been committed to making products that customers can trust for more than 10 years. Contact our Gold Service team to learn more.
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