Laser Fusion Cutting

In principle, the cutting of metals with the laser is effected by locally heating the material to above melting point at the focal point of the focused laser beam. The resulting smelt is ejected by a gas that is injected coaxially to the laser beam, so that an open cut is formed. In the case of high-alloy steels and aluminum, in particular, an inert gas (nitrogen, argon) is typically used as the cutting gas. This process, known as laser fusion cutting, is effected solely by the energy in the laser beam. The laser power required is therefore higher than for laser flame cutting. Laser fusion cutting does not oxidize the cut edges, which is particularly important when welding is the next process step after cutting. Today, laser fusion cutting is used industrially for material up to 25 mm thick, though it must be noted that an appropriate width of cut for the ejection of the smelt must be taken into account as the thickness of the material increases.

In principle, both CO₂ and Nd:YAG lasers are suitable for this application. The decision for one or other beam source is influenced by such factors as the geometry of the cut, the cycle time, the system technology and above all the material. Cutting in two dimensions, which is the most common case, is the domain of the CO₂ laser, because it yields the bast cost-benefit ratio. Typical cutting speeds in steel are, for example, in the region of approx. 8 meters per minute for 1 mm, 4.5 meters per minute for 3mm and 1.5 meters per minute for 8 mm thick material.