The quality of laser cutting refers to the precision of cutting dimension and the quality of cutting surface. The quality of cutting surface is generally measured by the following four indicators: The width of the cut;
The roughness of the cut surface;
Width of heat affected zone; Corrugation of cut section;
Whether there is slag on the cut section or the lower surface.
The main factors affecting the surface quality of laser cutting are as follows:
1.The laser used for cutting shall have high beam quality. Laser cutting is a process based on thermal effect. In order to obtain high power density and fine notch, the focus spot diameter should be small. At the same time, in order to ensure the consistency of cutting quality along different directions, the laser beam should have good rotational symmetry around the optical axis, circular polarization and high stability in the emission direction, so as to ensure the stability of the focus spot position. Modern lasers should also have the function of continuous and high repetitive output fast switching to ensure high-quality cutting of complex contours.
2.Thickness of focusing lens and plate: the lens focal length shall be selected according to the thickness of the material to be cut, taking into account the focusing spot diameter and focal depth. If the material is thick, the focal length should be large, otherwise, the focal length should be small. The focus spot position shall be close to the workpiece surface, and generally the focus shall be located at about 1/3 of the plate thickness below the upper surface of the plate.
3.Air flow and nozzle: the air flow in the laser cutting machine can blow away molten materials, protect the focusing lens and even provide part of cutting energy. The gas pressure and flow rate are important factors affecting the cutting quality. The pressure is too low to blow away the molten material at the notch; Too high, it is easy to form eddy current on the surface of the workpiece, which weakens the role of air flow in removing molten materials. Practice has proved that different nozzle structures have different effects on cutting.
4.The cutting speed of laser cutting outsourcing processing depends on the power density of the laser and the thermophysical properties and thickness of the material to be cut. Under certain cutting conditions, there is a reasonable range of cutting speed. If the cutting speed is too high, the cutting slag is not cleaned completely, or even the cutting is not penetrated. If the cutting speed is too low, the material is burned, and the cutting width and heat affected zone are large.
5.Cutting path: for the cutting of parts with complex contour or inflection point, due to the change of acceleration, it is easy to overheat and melt at the inflection point and form a collapse angle. Therefore, a reasonable cutting path is one of the effective ways to avoid this phenomenon.
