Principle and category of laser cutting

Laser cutting is to use a focused high power density laser beam to irradiate the workpiece, so that the irradiated material can rapidly melt, vaporize, ablate or reach the ignition point. At the same time, the molten material can be blown away with the help of high-speed air flow coaxial with the beam, so as to cut the workpiece. Laser cutting is one of the thermal cutting methods. The principle of laser cutting is shown in the figure below.

Laser cutting can be divided into laser vaporization cutting, laser melting cutting, laser oxygen cutting and laser scribing and controlled fracture.

Folding laser vaporization cutting

Use the laser beam with high energy density to heat the workpiece, make the temperature rise rapidly, reach the boiling point of the material in a very short time, and the material begins to vaporize and form steam. The steam spews out at a high speed, and at the same time, it forms a notch on the material. The heat of vaporization of materials is generally large, so laser vaporization cutting requires a large power and power density.

Laser vaporization cutting is mostly used for cutting extremely thin metal materials and non-metallic materials (such as paper, cloth, wood, plastic and rubber).

Folding laser melting and cutting

During laser melting and cutting, the metal material is melted by laser heating, and then non-oxidizing gases (Ar, He, N, etc.) are sprayed through the nozzle coaxial with the beam, and the liquid metal is discharged by the strong pressure of the gas to form a cut. Laser melting cutting does not need to completely vaporize the metal, and the required energy is only 1/10 of that of vaporizing cutting.

Laser melting cutting is mainly used for cutting some materials that are not easy to oxidize or active metals, such as stainless steel, titanium, aluminum and its alloys.

Folding laser oxygen cutting

The principle of laser oxygen cutting is similar to oxyacetylene cutting. It uses laser as preheating heat source and oxygen and other active gases as cutting gas. On the one hand, the injected gas reacts with the cutting metal to produce oxidation reaction and release a large amount of oxidation heat; On the other hand, molten oxides and molten substances are blown out of the reaction zone to form a notch in the metal. Because the oxidation reaction in the cutting process produces a large amount of heat, the energy required for laser oxygen cutting is only 1/2 of that for melting cutting, and the cutting speed is far greater than that of laser vaporization cutting and melting cutting.

Laser oxygen cutting is mainly used for carbon steel, titanium steel, heat treatment steel and other easily oxidized metal materials.

Folding laser scribing and controlling fracture

Laser scribing is to use a high energy density laser to scan the surface of a brittle material, make the material evaporate into a small groove, and then apply a certain pressure, the brittle material will crack along the small groove. The lasers used for laser scribing are generally Q-switched lasers and CO2 lasers.

Controlled fracture is to use the steep temperature distribution generated by laser grooving to generate local thermal stress in brittle materials, and make the materials break along the small groove.