Laser is an enhanced light obtained by stimulated radiation.

Its basic characteristics:

High intensity and brightness

The wavelength and frequency are determined, and the monochromaticity is good.

Good coherence and long coherence length

Good directivity, almost a beam of parallel light.

When the laser beam irradiates the surface of the workpiece, the light energy is absorbed and converted into heat energy, which makes the temperature of the irradiation point rise rapidly, melt and vaporize, and form small pits. Due to thermal diffusion, the metal around the light spot melts, and the metal vapor in the small pit expands rapidly, resulting in a micro-explosion, which ejects the melt at high speed and produces a strong directional back shock wave, so a hole with a big top and a small bottom is punched on the machining surface.

Comparison between ordinary light and laser

Generation of laser

Laser generated gas

Characteristics of laser cutting

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

(1) Good cutting quality

Laser cutting can obtain better cutting quality because of its small laser spot, high energy density and fast cutting speed.

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

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

(3) After laser cutting, the width of the heat affected zone is very small, and the properties of materials near the notch are almost unaffected, and the workpiece deformation is small, the cutting accuracy is high, the geometric shape of the notch is good, and the cross-sectional shape of the notch presents a regular rectangle. See table 1 for the comparison of laser cutting, oxyacetylene cutting and plasma cutting methods, and the cutting material is 6.2mm thick low-carbon steel plate.

(2) high cutting efficiency

Due to the transmission characteristics of laser, laser cutting machines are generally equipped with multiple CNC tables, and the whole cutting process can be fully CNC. When operating, just change the numerical control program, which can be applied to cutting parts with different shapes, both for two-dimensional cutting and three-dimensional cutting.

(3) fast cutting speed

Using laser with power of 1200W to cut 2mm thick low-carbon steel plate, the cutting speed can reach 600 cm/min; Resin plate cutting speed of 5mm thick polypropylene can reach 1200cm/min. There is no need to clamp and fix the material during laser cutting, which can not only save the fixture, but also save the auxiliary time of loading and unloading.

(4) Non-contact cutting

There is no contact between the cutting torch and the workpiece during laser cutting, and there is no tool wear. Machining parts with different shapes does not need to change "tools", only the output parameters of laser need to be changed. The laser cutting process has low noise, small vibration and no pollution.

(5) There are many kinds of cutting materials.

Metal matrix composites, leather, wood and fiber, etc. However, different materials show different laser cutting adaptability because of their different thermophysical properties and laser absorption rate. Using CO2 laser, the laser cutting performance of various materials is shown in Table 2.

(6) Disadvantages

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

Laser cutting equipment has high cost and large one-time investment.

Application scope of laser cutting

Most laser cutting machines are controlled by numerical control programs or made into cutting robots. As a precision machining method, laser cutting can cut almost all materials, including two-dimensional cutting or three-dimensional cutting of metal sheets.

In the field of automobile manufacturing, the cutting technology of roof window and other spatial curves has been widely used. Volkswagen uses a laser with a power of 500W to cut the body sheet and various curved parts with complex shapes. In the aerospace field, laser cutting technology is mainly used to cut special aviation materials, such as titanium alloy, aluminum alloy, nickel alloy, chromium alloy, stainless steel, beryllium oxide, composite materials, plastics, ceramics and timing. Aerospace parts processed by laser cutting include engine flame tube, titanium alloy thin-walled casing, aircraft frame, titanium alloy skin, wing stringer, tail plate, helicopter main rotor, space shuttle ceramic heat insulation tile, etc.

Laser cutting forming technology is also widely used in the field of non-metallic materials. It can not only cut high-hardness and brittle materials, such as silicon nitride, ceramics, aging and so on. It can also cut and process flexible materials, such as cloth, paper, plastic board, rubber and so on. If you use laser to cut clothes, you can save 10% 12% of clothing materials and improve the efficiency by more than 3 times.

The process of laser processing

Laser light path

Laser generator

Carving head

From drawings to parts

Factors affecting cutting

Cutting gas

Focus position

How to improve cutting quality