Before cutting, the distance between laser focus and cutting material must be adjusted. Different focus positions often lead to different fineness of cutting material section, different slag hanging at the bottom, and even unable to cut off the material; Different cutting workpiece, different materials, laser cutting machine focus position selection will be different, so how to choose correctly?
That is, the cutting focus is on the workpiece, and the focus is located above the cutting material.
For carbon steel oxygen cutting, it is suitable to use positive focus. The cutting range of the bottom of the workpiece is larger than that of the upper surface, which is conducive to slag removal and oxygen reaching the bottom of the workpiece to participate in full oxidation reaction. In a certain range of focus, the larger the positive focus is, the larger the spot size is, the more sufficient the preheating and heat supplement around the slit is, and the smoother and brighter the carbon steel cutting surface is.
For the 10000 watt laser pulse mode cutting stainless steel thick plate, the positive focus is adopted, the cutting is stable, which is conducive to slag removal and is not easy to reverse blue light;
2.Negative focus cutting
That is, the cutting focus is in the workpiece. In this mode, because the focus is far away from the cutting surface, the cutting range is relatively larger than that of the cutting point on the workpiece surface, and the cutting air flow and temperature need to be large and sufficient.
When cutting stainless steel, it is suitable to use negative focus cutting, the cutting surface is even and the section is good.
For the plate perforation before cutting, because the perforation has a certain height, the negative focus is adopted to ensure the minimum spot size and the maximum energy density at the perforation position, and the deeper the perforation position is, the larger the negative focus is.
3.Zero focus cutting
That is, the cutting focus is on the surface of the workpiece. The cutting surface close to the focus is relatively smooth, while the lower surface away from the cutting focus is rough. This is mainly used for cutting thin plates and pulse laser peak power vaporization to cut metal foil.
The choice of the positive and negative focus of laser cutting is not determined by the cutting plate material (stainless steel, carbon steel), but by the cutting method (oxidation cutting, melting cutting).