We usually refer to the distance of the upper surface of the workpiece processed by the focal length as the focal length of the upper and lower parts of the workpiece. The focus position above the workpiece is generally called positive focus, and the focus position below the workpiece is generally called negative focus. Changing the focusing position means changing the size of the light spot, which increases the focusing distance, thickens the light spot and widens the gap, thus affecting the heating area, focusing distance and slag discharge.
Positive focus cutting means that the cutting focus is on the workpiece and the cutting focus is on the material. When the carbon steel is cut by oxygen positive polymerization, the cutting width of the lower cutting surface is larger than that of the upper cutting surface, which is conducive to slag discharge. The oxygen reaching the lower cutting surface participates in the full oxidation reaction. In the range of focal length, the larger the positive focus amount, the larger the spot size of the plate surface is; and the more sufficient the preheating and heat source supplement, and the smoother and cleaner the carbon steel cutting surface is. The 10000 watt pulsed laser is used to cut thick stainless steel plates. The positive focus cutting is more stable, conducive to slag removal, and not easy to produce blue light.
Negative focus cutting means that the focus of cutting is on the workpiece. Because the focus is far away from the cutting surface, the cutting width is larger than the cutting width of the workpiece, and the required cutting air flow is large enough and the temperature is high enough. When cutting stainless steel, the negative focus cutting effect is good, the cutting surface has even lines, and the section is good. Before cutting, because the perforation has a certain height, negative focusing can minimize the spot size on the hole location and maximize the energy density. The greater the hole depth, the better the negative focusing effect.
Zero focus cutting, that is, the cutting focus is the surface of the workpiece. The cutting surface near the focus is usually smooth, while the surface away from the focus is rough. The invention is mainly applied to continuous thin sheets laser cutting, and pulse laser cutting high peak power evaporation foil.
The selection of the cutting point in the laser cutter does not depend on the material of the cutting plate (stainless steel and carbon steel), but on the cutting method (oxidation cutter and melting cutter).
How to Select the Focus Position of Laser Cutting Machine?
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