SPG OF LASER WELDING

There are two different approaches to laser welding. One is the low-power method for relatively thin materials; and the other is the "brute force" high-power approach that generally involves keyholing. In both cases, since filler material is rarely used, a tight fitup of the parts being welded is necessary. For butt and seam welds, the laser energy is applied to the junction of the materials, minimizing heat input and distortion and permitting high processing speeds. However, these butt joints must fit accurately, which often limits laser butt welding to circular parts which can be turned to close tolerances and press-fit together prior to welding.

For lap joints, the tolerances for seam alignment are somewhat looser. The width of the weld is the major consideration. The upper material forms most of the fusion zone so that a good laser-weldable material could be welded to less suitable material by putting the former material on top.

Slow-axial-flow lasers with enhanced pulsed capabilities offer an advantage over fast-axial-flow units for applications requiring rapid energy coupling and low heat input. In pulsed operation, the peak power in the pulse is several times greater than the continuous-wave power, although the average power is lower. This peak power overcomes surface reflectivity and minimizes thermal damage to the surrounding material.

Solid state lasers (the generic name for Nd:YAG, Nd:Glass and similar lasers), are preferred for low- to moderate- power applications. They have found extensive application in the electronic/electrical industries for spot welding and beam lead welding integrated circuits to thin film interconnecting circuits on a substrate.

One consideration that can be important in evaluating laser welding is the physical size of the equipment. Solid state laser welding systems are relatively small compared to CO2 systems, which could occupy an average room to achieve the high powers required. Still, if you need the brute power, it can be guided to the workpiece through optics or articulating arms (attached to robots, if desired).