Compared with traditional oxyacetylene and plasma cutting processes, laser cutting has the advantages of fast cutting speed, narrow cutting seam, small heat affected zone, good perpendicularity of cutting seam edge and smooth cutting edge.
At the same time, there are many kinds of materials that can be laser cut. Laser cutting technology has been widely used in automobiles, machinery, electric power, hardware and electrical appliances.
Several key technologies of laser cutting machine are the integrated technology of optical, mechanical and electrical integration.
In laser cutting machine, the parameters of the laser beam, the performance and accuracy of the machine and NC system directly affect the efficiency and quality of laser cutting.
Cutting accuracy is the first factor to judge the quality of NC laser cutting machine. So, what are the factors affecting the cutting quality of laser cutting machine?
The factors affecting the cutting quality of laser cutting machine include cutting speed, focus position, auxiliary gas, laser output power and workpiece characteristics, which are analyzed in detail below.
The laser cutting machine generates energy from continuous-wave output laser beam. Laser power and mode selection will have an impact on cutting quality.
In actual operation, it is usually adjusted to a higher power to meet the cutting of thicker materials. At this time, the beam mode (the distribution of beam energy in the cross-section) is more important.
Under the condition of less than high power, the focus obtains higher power density and better cutting quality.
The modes are not consistent throughout the effective working life of the laser.
The condition of optical elements, the slight change of laser working gas mixture and flow fluctuation will affect the mode mechanism.
The relative position between the focus and the workpiece surface is particularly important to ensure the cutting quality.
In most cases, when cutting, the focus position is just on the workpiece surface or slightly below the surface.
In the whole cutting process, ensuring the constant relative position between the focus and the workpiece is an important condition to obtain stable cutting quality.
When the focus is in a better position, the slit is smaller, the efficiency is higher, and a better cutting speed can obtain a better cutting result.
In most applications, the beam focus is adjusted to just under the nozzle. The distance between the nozzle and workpiece surface is generally about 1.5mm.
After the laser beam is focused, the spot size is directly proportional to the focal length of the lens.
After the beam is focused by the short focal length lens, the spot size is very small, and the power density at the focus is very high, which is very beneficial to material cutting;
The disadvantage is that the focal depth is very short and the adjustment allowance is small.
It is more suitable for high-speed cutting of thin materials.
The long focal length lens has a wide focal depth and sufficient power density, which is more suitable for cutting thick workpieces.
The cutting speed of materials is directly proportional to the laser power density, that is, increasing the power density can improve the cutting speed.
The cutting speed is inversely proportional to the density (specific gravity) and thickness of the material being cut.
When other parameters remain unchanged, the factors to improve the cutting speed are: increase the power (within a certain range, such as 500 ~ 2000 W);
Improve the beam mode (e.g. from high-order mode to low-order mode to TEM00);
Reduce the focus spot size (e.g. focusing with a short focal length lens);
Cutting materials with low initial evaporation energy (such as plastic, plexiglass, etc.);
Cutting low-density materials (such as white pine, etc.); Cut thin material.
Auxiliary gas is required for material cutting with laser cutting machine, and the gas pressure is a very important factor.
The auxiliary gas is ejected coaxially with the laser beam to protect the lens from pollution and blow away the slag at the bottom of the cutting area.
For non-metallic materials and some metallic materials, use compressed air or inert gas to treat melted and evaporated materials and inhibit excessive combustion in the cutting area.
For most metal laser cutting, active gas (as long as O2) is used to form oxidation exothermic reaction with hot metal.
This additional heat can increase the cutting speed by 1 / 3 ~ 1 / 2. When cutting thin materials at high speed, higher gas pressure is required to prevent slag sticking on the back of the cut (hot slag sticking to the workpiece will also damage the cutting edge).
When the material thickness increases or the cutting speed is slow, the gas pressure should be appropriately reduced.
In order to prevent the frosting of plastic cutting edge, it is also better to cut with lower gas pressure.