Influencing factors of laser cutting processing quality

November 25, 2022
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The quality of laser cutting refers to the accuracy of the cutting size and the quality of the cutting surface. The quality of the cutting surface is generally measured by the following four indicators: the width of the incision and the surface roughness of the incision; the width of the heat-affected zone; the corrugation of the incision section ; Whether there is dross on the cut section or the lower surface. The main factors affecting the surface quality of laser cutting are as follows:

1. Laser for cutting, the laser should have high beam quality. Laser cutting is a process based on thermal effects. In order to obtain high power density and fine incision, the diameter of the focus spot should be small. At the same time, in order to ensure the consistency of cutting quality in different directions, the laser beam should have good rotational symmetry around the optical axis. And circular polarization and high emission direction stability to ensure that the focused spot position is stable. Modern lasers should also be capable of fast switching between continuous and high-repetition outputs to ensure high-quality cutting of complex contours.

2. The thickness of the focusing lens and the plate, the focal length of the lens is selected according to the thickness of the material to be cut, taking into account the diameter of the focusing spot and the depth of focus. If the material is thick, the focal length should be large, otherwise, the focal length should be small. The position of the focus spot should be close to the surface of the workpiece. Generally, the focus should fall on the lower part of the upper surface of the plate about 1/3 of the thickness of the plate.

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3. Airflow and nozzle. The airflow in the laser cutting machine has the function of blowing off the molten material, protecting the focusing lens and even providing part of the cutting energy. The gas pressure and flow rate are important factors affecting the cutting quality. If the pressure is too low, the molten material at the incision cannot be blown away; if it is too high, it is easy to form a vortex on the surface of the workpiece, which weakens the effect of the airflow on removing the molten material. Practice has proved that nozzles with different structures will 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 cutting speed range. If the cutting speed is too high, the slag will not be cleared completely, or even cut through. If the cutting speed is too low, the material will be over-burned, and the kerf width and heat-affected zone will be large.

5. Cutting trajectory. For the cutting of complex contours or parts with inflection points, due to the change of acceleration, it is easy to overheat and melt the inflection point to form a collapse angle. Therefore, a reasonable cutting trajectory is one of the effective ways to avoid this phenomenon.