Classification and application of laser metal sheet metal processing

Classification of laser cutting machines

According to the different laser generator, it can be divided into three laser cutting machines: CO2 laser cutting machine, YAG (solid state) laser cutting machine, fiber laser cutting machine.

CO2 laser cutting machine

CO2 laser cutting machine is equipped with a nozzle at the beam exit to spray oxygen, compressed air or the inert gas N2, which is used to improve the cutting speed and ensure the smooth and clean incision.In order to improve the stability and life of power supply, the discharge stability of high power laser should be solved by CO2 gas laser.

YAG (solid) laser cutting machine

YAG laser cutting machine is mainly used for drilling and spot welding and sheet cutting.Its green laser beam can be used in the case of pulse or continuous wave, with short wavelength, good light concentration, suitable for precision machining, especially in the case of pulse hole machining, can also be used for cutting, welding and photolithography.The wavelength of YAG solid laser cutting machine is not easy to be absorbed by non-metallic materials, so it cannot cut non-metallic materials, and YAG solid laser cutting machine needs to improve the stability of power supply and life.It is necessary to develop a light source with large capacity and long life by using semiconductor light pump.

Fiber optic laser cutting machine

Optical fiber laser cutting machine can be transmitted through optical fiber, the degree of flexibility has been unprecedented improved, fewer fault points, convenient maintenance, fast, in the cutting of thin plate within 4mm has a great advantage, but due to the influence of the wavelength of solid laser, its quality in cutting thick plate is poor.The wavelength of optical fiber laser cutting machine is 1.06 m, not easy to be absorbed by non-metallic materials, so can not cut non-metallic materials.The photoelectric conversion rate of optical fiber laser is as high as 25%. The optical fiber laser has obvious advantages in the aspects of electricity consumption and supporting cooling system parameters.According to the international safety standards, optical fiber laser is the most harmful class because of the length of the wave.For safety reasons, optical fiber laser processing needs to be carried out in a completely closed environment.As a new laser technology, fiber laser cutting machine is far less popular than CO2 laser cutting machine.

 

Laser fusion cutting

(1) laser melting cutting, the workpiece is partially melted after the use of airflow to melt the material jet out.Because the transfer of material occurs only in its liquid state, the process is called laser-fusion cutting.

(2)The laser beam with a high purity inert cutting gas to force the melted material to leave the slit, the gas itself does not participate in the cutting.

(3) Laser melting cutting can get a higher cutting speed than gasification cutting.The energy required to vaporize is usually higher than that required to melt the material.In laser fusion cutting, the laser beam is only partially absorbed.

(4) The maximum cutting speed increases with the increase of laser power, as the thickness of the plate increases and the melting temperature of the material increases and decreases inversely proportional.When the laser power is constant, the limiting factors are the air pressure at the slit and the thermal conductivity of the material.

5) laser melting cutting for iron materials and titanium metal can be obtained without oxidation notch.For steel materials, the laser power density which melts but is not gasified is between 104W/cm2 and 105W/cm2.
 

Laser flame cutting

Laser flame cutting differs from laser melting in that it USES oxygen as the cutting gas.With the help of oxygen and the interaction between the heated metal, a chemical reaction takes place to heat the material further.For structural steel of the same thickness, the cutting rate obtained by this method is higher than that by melting.

On the other hand, the quality of the cut is worse than that of the fusion cut.It actually produces wider slits, greater roughness, increased heat affected area and poorer edge quality.

(1) Laser flame cutting in the processing of precision models and sharp corners is defective (there is a risk of burning off sharp corners).A pulsed mode laser can be used to limit the heat-affected area.

(2)The laser power used to determine the cutting speed.When the laser power is constant, the limiting factors are the supply of oxygen and the thermal conductivity of the material.

 

Laser gasification cutting

During laser gasification cutting, the material is vaporized at the slit, which requires very high laser power.To prevent condensation of the material on the slit wall, the thickness of the material must not be significantly greater than the laser beam diameter, and this process is therefore only suitable for use without the discharge of the melted material.This process is actually only used in very small areas of ferrous alloys.

(1) laser gasification cutting, the optimal beam focus depends on the material thickness and beam quality.

(2)The laser power and gasification heat on the optimal focus location has a certain effect.

(3) Under a certain thickness of the plate, the maximum cutting speed is inversely proportional to the material gasification temperature.

(4) The required laser power density is greater than 108W/cm2, depending on the material, cutting depth and beam focus location.

(5) there is a certain thickness of the plate.Assuming sufficient laser power, the maximum cutting speed is limited by the gas jet velocity.