Laser cutting types

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

1. Laser vaporization cutting

Using a laser beam with high energy density to heat the workpiece, the temperature rises rapidly, reaching the boiling point of the material in a very short time, and the material begins to vaporize and form steam. The speed of these vapors is very high, and at the same time the vapor is emitted, a notch is formed in the material. The heat of vaporization of the material is generally large, so the 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, etc.).

2. Laser melting cutting

When laser melting cutting, the metal material is melted by laser heating, and then non-oxidizing gas (Ar, He, N, etc.) is sprayed through the nozzle coaxial with the beam, and the liquid metal is discharged by the strong pressure of the gas to form the incision. Laser melting cutting does not require the metal to be completely vaporized, and the energy required is only 1/10 of that of vaporized cutting.

Laser melting cutting is mainly used for the cutting of some non-oxidizing materials or active metals, such as stainless steel, titanium, aluminum and its alloys.

3. Laser oxygen cutting

The principle of laser oxygen cutting is similar to oxy-acetylene cutting. It uses a laser as a preheating heat source and an active gas such as oxygen as a cutting gas. On the one hand, the gas blown out interacts with the cutting metal to undergo oxidation reaction and release a large amount of oxidation heat; On the other hand, the molten oxide and melt are blown out of the reaction zone, forming a notch in the metal. Due to the oxidation reaction in the cutting process produces a lot of heat, so the energy required for laser oxygen cutting is only 1/2 of the melting cutting, and the cutting speed is much greater than the laser vaporization cutting and melting cutting. Laser oxygen cutting is mainly used for carbon steel, titanium steel and heat-treated steel and other easily oxidized metal materials.

4. Laser scribing and control fracture

Laser scribing is the use of high energy density laser scanning on the surface of the brittle material, so that the material is heated to evaporate out of a small slot, and then apply a certain pressure, the brittle material will be split along the small slot. The lasers used for laser scribing are generally Q-switched lasers and CO2 lasers.

Controlled fracture is the use of the steep temperature distribution generated by laser grooving to create local thermal stress in the brittle material, causing the material to break along the small grooves.

peculiarity

Compared with other thermal cutting methods, laser cutting is generally characterized by fast cutting speed and high quality. Specifically summarized in the following aspects.

⑴ Good cutting quality

Because the laser spot is small, the energy density is high, and the cutting speed is fast, the laser cutting can obtain better cutting quality.

① The laser cutting incision is narrow, both sides of the slit are parallel and perpendicular to the surface, and the dimensional accuracy of the cutting parts can reach ±0.05mm.

② The cutting surface is clean and beautiful, the surface roughness is only tens of microns, and even laser cutting can be used as the last process, without mechanical processing, and the parts can be used directly.

③ After the material is laser cut, the width of the heat affected zone is small, the performance of the material near the slit is almost unaffected, and the workpiece deformation is small, the cutting precision is high, the geometry of the slit is good, and the cross-section shape of the slit is more regular rectangular. The comparison of laser cutting, oxy-acetylene cutting and plasma cutting methods is shown in Table 1. The cutting material is 6.2mm thick mild steel plate.

(2) High cutting efficiency Due to the transmission characteristics of the laser, the laser cutting machine is generally equipped with multiple numerical control tables, and the entire cutting process can be fully CNC. When operating, just change the numerical control program, it can be applied to cutting parts of different shapes, both two-dimensional cutting and three-dimensional cutting can be achieved.

(3) Fast cutting speed

Cutting 2mm thick low carbon steel plate with 1200W laser power, cutting speed up to 600cm/min; Cutting 5mm thick polypropylene resin plate, cutting speed up to 1200cm/min. The material does not need to be fixed in the laser cutting, which can save the fixture and save the auxiliary time of loading and unloading.

⑷ Non-contact cutting

There is no contact between the torch and the workpiece during laser cutting, and there is no tool wear. Processing parts of different shapes, do not need to replace the "tool", just change the output parameters of the laser. Laser cutting process has low noise, low vibration and no pollution.

(5) There are many kinds of cutting materials

Compared with oxy-acetylene cutting and plasma cutting, there are many types of laser cutting materials, including metal, non-metal, metal base and non-metal base composite materials, leather, wood and fiber. However, for different materials, due to their thermal physical properties and different absorption rates of laser, they show different laser cutting adaptability. Using CO2 laser, the laser cutting performance of various materials is shown in Table 2.

Due to the limitations of laser power and equipment volume, laser cutting can only cut plates and pipes of medium and small thickness, and with the increase of workpiece thickness, the cutting speed decreases significantly.