Introduction of four commonly used laser cutting heads
1. Melt the cutting head
In laser fusion cutting head cutting, the workpiece is partially melted, and then the melted material is sprayed through an air stream. Since the material transfer only occurs in the liquid state, the process is called laser fusion cutting head cutting. When the laser melting cutting head cuts, of course, the material is heated to a certain temperature to melt, and then the non-oxidizing gas is injected through the nozzle coaxial with the beam, and the liquid metal is discharged by the pressure of the gas to form a cut. The energy required for the laser melting cutting head is only 1/10 of that for vaporized cutting, and the metal does not need to be completely vaporized. Laser fusion cutting can achieve oxidation-free cutting of iron materials and titanium metals. For steel materials, the power density of the laser head producing molten but less than vaporized is between 104W/cm2 and 105W/cm2.
2. Evaporation cutting head
In the cutting process of the laser vaporization cutting head, the high-energy and high-density laser head beam is used to heat the workpiece to increase the temperature, and the material evaporates into steam in a very short time. When the steam is ejected, a cut is formed in the material, thereby achieving the cutting effect. However, the heat of vaporization of general materials is very large, so the surface temperature of the material is raised to the boiling point temperature, so the melting caused by heat conduction can be avoided, so that some materials evaporate into steam and disappear, and some materials are swept from the slit by the auxiliary air flow The bottom acts as an ejector. Very high laser head power is required in this case.
To prevent material vapor from condensing onto the slit walls, the thickness of the material should not greatly exceed the diameter of the laser head beam. Therefore, this method is only suitable for applications where exclusion of molten material must be avoided. Materials used for cutting by laser evaporation cutting heads typically include extremely thin metallic and non-metallic materials. When the thickness of the plate is steady state, the maximum cutting speed is inversely proportional to the vaporization temperature of the material. The required laser head power density is greater than 108W/cm2, depending on the material, cutting depth and beam focus position. At a certain thickness of the plate, assuming sufficient laser power, the maximum cutting speed is limited by the gas injection rate.
3. Control the fracture cutting head
For brittle materials that are easily damaged by heat, high-speed and controlled cutting is performed by heating the laser head beam, which is called controlled fracture cutting. The main content of the cutting process is: the laser head heats a small piece of brittle material, resulting in a large thermal gradient and severe mechanical deformation, resulting in cracks in the material. The laser head can guide cracks in any desired direction as long as a uniform heating gradient is maintained. Common materials used for such cuts are brittle materials.
4. Oxidation melting cutting head (laser flame cutting head)
Typically, an inert gas is used to melt the cutting head for cutting. If oxygen or other reactive gas is used instead, the material will be ignited under the irradiation of the laser head beam and will react violently with the oxygen to generate an additional heat source to further heat the material, which is called oxidative fusion cutting head cutting. Due to this effect, for structural steel of the same thickness, the cutting rate obtained by this method is higher than that obtained by melt cutting. On the other hand, this method may have worse kerf quality than fusion cutting head cuts. In fact, it produces wider cuts, noticeable roughness, increased heat-affected zone and poorer edge quality. Laser head flame cutting is not suitable for machining precise models and sharp corners (there is a danger of burning at sharp corners).
