Fast cutting speed is one of the advantages of fiber laser cutting machines, but the cutting speed is not as fast as possible. In the case of a certain laser power, it is necessary to select an appropriate cutting speed according to the plate, so as to make the cutting surface beautiful and obtain high-quality cutting workpieces. When you use a fiber laser cutting machine, you can judge whether the cutting speed is appropriate by the following methods, and then adjust the cutting speed:
Observe the cutting sparks: When the cutting speed is appropriate, the cutting sparks spread evenly from top to bottom. When the cutting speed is too fast, the cutting spark will tilt. When the cutting speed is too slow, the cutting sparks gather together, do not spread and are small.
Observe the cutting plate: when the cutting speed is appropriate, the cutting surface presents a relatively smooth line, and there is no slag in the lower half. When the cutting speed is too fast, the cutting section will be slanted, and the lower part will produce slag; at the same time, it may also cause the plate to be unable to be cut through, and sparks will spray. When the cutting speed is too slow, it will cause over-melting, the cutting surface will be rough, and the kerf will become wider.
2.Nozzle and Nozzle Height
As the beam and auxiliary gas channel, the shape, aperture and height of the nozzle will affect the cutting effect. The nozzle is mainly used to control the area and size of gas diffusion, so as to control the cutting quality and prevent debris such as slag from bouncing upwards, passing through the nozzle and contaminating the lens.
In general, when cutting thin plates, the defocus amount is small, and a small diameter nozzle is used. However, when cutting thick plates, a large kerf and a large spot are required, and a large-diameter nozzle is used.
The nozzle is divided into single layer and double layer. Single-layer laser nozzles are used for fusion cutting, that is, using nitrogen as an auxiliary gas, usually for cutting stainless steel and aluminum plates, etc. Double-layer laser nozzles are generally used for oxidative cutting, that is, using oxygen as an auxiliary gas, usually for cutting carbon steel.
The nozzle height is the distance between the nozzle outlet and the workpiece surface. When cutting, this height is generally set at 0.3mm-0.8mm. If the nozzle height is set too low, the nozzle will easily collide with the surface of the workpiece. If the nozzle height is set too high, the concentration and pressure of the auxiliary gas will be reduced, resulting in a decrease in the cutting quality. When perforating, in order to prevent the generated slag from being reflected on the lens, the height of the nozzle can be appropriately raised.
In the actual cutting process, we need to set the appropriate focus position to obtain the workpiece with better cutting effect:
Zero focal length: The focus is on the surface of the workpiece, which is suitable for cutting thin sheets.
Negative focal length: The focus is under the surface of the workpiece, generally at 1/2-2/3 of the thickness of the workpiece, so the range of the smooth surface is larger, and the slit will be wider than the zero focal length.
Positive focal length: The focus is on the upper surface of the workpiece, which is generally suitable for the cutting of thick carbon steel (thick plates require larger slits, and a negative focus will lead to overburning of carbon steel).
4. Auxiliary Gas Pressure
Insufficient air pressure: When the gas pressure is insufficient, the slag produced by cutting cannot be removed, and it is not easy to penetrate, resulting in slag on the cutting surface, which also affects the efficiency of cutting. In general, when cutting thin plates at high speed, high air pressure is required to prevent slag from attaching to the back of the slit; when the material is thicker or the cutting speed is slow, the air pressure can be appropriately reduced.
Excessive air pressure: Increasing the air pressure can improve the cutting speed to a certain extent, but excessive air pressure will reduce the cutting speed.This is because under high pressure, too fast gas flow will enhance the cooling effect and even interfere with the focusing of the beam energy, resulting in a decrease in cutting quality and efficiency. At the same time, when the air pressure is too high, the cutting surface will be rough and the kerf will be wider.