Laser Beam Shaping and Beam Wiggling

Beam Shaping

When we talk about Beam Shaping, we often refer to the use of beam shaping lenses, lenses, microlenses or different shaped fibers to achieve a homogenizing effect on the spot. Here we introduce a new method: BrightLine welding technology from TRUMP, using a 2-in-1 fiber (Figure 1), which is composed of an inner fiber core and an outer fiber ring. The two beams are superimposed to act on the processing area.

Figure 1 TRUNP's 2-in-1 fiber optic technology Figure 3 Linear motion and up-and-down oscillation superimposed trajectory

In the Deep Penetration Process, the metal in the tiny location is melted and vaporized by the laser heat, creating a high-pressure vapor at the bottom of the tiny hole. The steam is ejected from the bottom resulting in material loss, also known as spatter. The whole process is similar to boiling water at home that continuously generates bubbles. When using a 2-in-1 shaping beam, the outer ring fiber creates a larger area of "buffer" around the micro-aperture, allowing the high-pressure vapor to escape. The outer ring beam helps create a more stable deep fusion welding process.

At the same time, the outer ring beam changes the flow direction of the molten pool metal liquid (Figure 2). The molten metal flowing faster toward the surface is deflected to the side under the influence of the ring beam pulse. Thus, under the combined effect of these two changes, the internal and external fiber-optic shaping technique has been tested and proven to reduce spatter by 90%.

Figure 2 Change of melt pool under the action of internal and external beams

Beam Oscillation

The beam oscillation trajectory is shown in the figure below. For some butt and lap welding processes, where there is a gap between the parts and no filler material, conventional laser welding does not weld effectively because it follows a straight line along the gap. Therefore, beam oscillation (Oscillation or Wobble) is introduced, where straight and up-and-down movements are superimposed to create a spiral (Figure 3), increasing the molten pool area, where the metal liquid fills the gap to achieve the weld. The use of beam oscillation has the added benefit of compensating for dimensional errors in the part, reducing porosity and increasing the aesthetics of the weld and the stability of the welding process.

Figure 3 Straight-line motion and up-and-down oscillation superimposed trajectory

The simultaneous use of beam shaping and beam oscillation can greatly improve the stability of the deep-fusion welding process, improve the weldability of aluminum alloys and high-strength steels, and effectively avoid microcracking. However, for some materials, random micro-cracking still exists. Figures 4-6 below show the welding results of 6XXX series aluminum alloys under the three conditions of beam shaping, beam oscillation, and beam shaping and oscillation.

Figure 4 Beam shaping welding cross-section microscopic effect

Figure 5 Beam swing welding cross-section microscopic effect

Figure 6 Beam shaping and beam swing welding cross-section microscopic effect