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Laser Wobbling

Fiber Laser Wobble Welding

When producing welds for industries that rely on precision, a word like “wobble” might raise some red flags. In a world of tolerances on the micrometer level, wobble sounds sloppy. Where strength and consistency are paramount, wobble seems weak and inconsistent.
But sometimes it’s out-of-the-box thinking that leads to innovation. It’s these very factors that have brought laser welding to the center stage of high-tech industries – with its high welding speeds, small heat-affected zone and consistent welds.
But like all manufacturing processes, there’s room to improve. And laser welding is no different.
 

What is wobble laser welding?

Standard laser welding heads are designed to focus a collimated laser beam to a required spot size, keeping the beam path static through the beam delivery and a static spot at the focal plane.
This standard configuration limits each setup to a specific application.
Wobble heads, on the other hand, incorporate scanning (oscilation or wobbling) mirror and lenses technology inside a standard laser weld head.
By moving the beam with internal mirrors, the focal spot is no longer static, and can be dynamically adjusted by changing the shape, amplitude, and frequency.

Wobble-welding: revolution in laser welding

TREPANNING LASER WELDING HEAD

Fiber Laser wobble welding or Laser beam stir welding

Trepanning laser beam welding

Laser wobble welding or Laser beam stir welding is increasingly being utilized to improve weld quality, properties, and reliability for a wide range of industries, and improvements in laser beam quality and delivery capabilities are helping to spur this growth. The process has wide application in the automotive, aerospace, and fabrication industries, to name a few.

The term "laser stir welding" or laser wobble welding was coined to describe a process in which the laser keyhole or vapor cavity was manipulated or oscillated at a relatively high rate to cause a stirring action within a larger pool. It has also been referred to as laser beam welding with wobbling. The phenomena is centered upon proper selection of the energy density of the laser and relative rate and motion of beam oscillation based on the thermal properties of the material being processed.

The ultimate effect when the correct parameters are chosen is the integration of energy distributed over the beam oscillation area, allowing the keyhole to cause a hydrodynamic stirring action at the rapidly moving beam. The total energy integrated over the oscillation region is responsible for maintaining the large molten pool, while the local intensity of the beam sustains the vapor cavity during oscillation and stirring within the molten pool. The rapid motion of the oscillated beam establishes a self-healing nature of the keyhole.

Research conducted during the development of the process had shown that laser beam welds produced on alloys using the laser stir welding process displayed less weld defects when compared to traditional laser beam welding, along with concomitant benefits of increased size of the weld to accommodate gaps and improve shear strength of lap joints, and enhanced ability to feed filler material. It was also established that by proper selection of parameters that govern the input and distribution of energy in relation to the thermal diffusivity and fluidity of the base metal, the process is easily applied to other alloy systems.

Recent research and applications of laser stir welding have increased significantly since its inception, based on the underlying principle that rapid oscillation of the vapor cavity within the molten pool provides a hydrodynamic stirring action that may reduce defects related to gas absorption and keyhole instability, while also providing simultaneous benefits associated with the formation of a larger weld pool.

The principle of the laser stir welding process remains the same, but laser sources providing improved beam quality and galvanometer-based systems for beam manipulation enable the process to be effectively adopted and utilized for a broad range of industrial applications.

Fiber laser Wobble movement

oscillating scanning fiber laser

Fiber laser oscillation wobbling welding results

The wobble method produces a superior weld by greatly reducing imperfections, increasing consistency, reducing material cost and providing more tolerance for process variables.

Laser stir welding (wobble welding) involves the manipulation of the laser beam to provide hydrodynamic stirring and subsequent healing of the keyhole.

To achieve the wobble method, a fixed laser is optically manipulated with attachments, such as our wobble head, that allow the laser to wobble to a programmed pattern down the seam of the weld. The wobble method produces a superior weld by greatly reducing imperfections, increasing consistency, reducing material cost and providing more tolerance for process variables.

Laser Beam Welding Vs Laser Beam wobble Welding (or Laser beam stir welding)

Laser Beam Welding (LBW) is a material-joining technique that applies laser radiation to melt the base material and create the welding joint. Laser beam welding process is related to other traditional welding methods, such as electron beam welding (EBW), tungsten plasma arc welding (PAW), or inert gas tungsten arc welding (TIG).
Laser beam welding applies a high power industrial laser to create a narrow and deep melt pool between the parts to be welded. Laser is a highly concentrated heat source that can be easily automated and installed on industrial welding cells or mounted in a handheld gun like our wobble-3, providing high welding speeds for many industrial applications.
Nevertheless, factors such as the laser beam quality or the processed materials have a great influence on the resulting geometry, microstructure, and residual stress distribution. Therefore, final results are directly dependent on the process input parameters, which means that process parameters must be carefully selected for achieving the desired quality.
Laser Stir Welding (LSW) - (LWW Laser Wobble Welding) utilizes some form of beam manipulation to oscillate the keyhole or vapor cavity within a larger molten pool. It requires a relatively high rate of manipulation, which may be represented by circular motion or some other pattern. The manipulation of the beam, and its corresponding oscillation of the vapor cavity within the molten pool, is utilized in conjunction with motion used for the welding path.