Analysis of the Four Factors Affecting the Cutting Quality of Laser Cutting Machines – XT LASER Annie

Factors that affect the cutting quality of laser cutting machines include cutting speed, focus position, auxiliary gas, laser output power, and workpiece characteristics, etc., which will be analyzed in detail below.


1. Laser output power
The laser cutting machine generates energy from the continuous wave output laser beam, and the laser power and mode selection will have an impact on the cutting quality. In actual operation, it is usually adjusted to a higher power to meet the requirements of cutting thicker materials. This is where the beam pattern (the distribution of beam energy across the cross-section) becomes more important. Under the condition of less than high power, higher power density is obtained at the focal point, and better cutting quality is obtained. The mode is not consistent throughout the useful operating life of the laser. The condition of the optics, slight changes in the laser working gas mixture, and flow fluctuations all affect the mode mechanism.

2. Focus position adjustment
The relative position of the focal point and the workpiece surface is particularly important to ensure the cutting quality. In most cases, the focal position is just at or slightly below the surface of the workpiece when cutting. During the whole cutting process, ensuring that the relative position of the focal point and the workpiece is constant is an important condition for obtaining stable cutting quality. When the focus is in the best position, the kerf is smaller and the efficiency is higher, and the better cutting speed can get better cutting results. In most applications the beam focus is adjusted to be just below the nozzle. The distance between the nozzle and the surface of the workpiece is generally about 1.5mm.

After the laser beam is focused, the spot size is proportional to the focal length of the lens. After the beam is focused by a short focal length lens, the spot size is very small, and the power density at the focal point is very high, which is very beneficial to material cutting; the disadvantage is that the focal depth is very short, and the adjustment margin is small. Suitable for cutting thin materials at high speed. The telephoto lens has a wider depth of focus and sufficient power density, which is more suitable for cutting thick workpieces.

3. Cutting speed
The cutting speed of the material is directly proportional to the laser power density, that is, increasing the power density can increase the cutting speed. Cutting speed is inversely proportional to the density (specific gravity) and thickness of the material being cut. When other parameters remain unchanged, the factors to increase the cutting speed are: increase the power (in a certain range, such as 500 ~ 2 000W); improve the beam mode (such as from high-order mode to low-order mode until TEM00); reduce the focus spot size ( Such as using a short focal length lens to focus); cutting materials with low initial evaporation energy (such as plastics, plexiglass, etc.); cutting low-density materials (such as white pine, etc.); cutting thin materials

4. Auxiliary gas pressure
The use of auxiliary gas is required for cutting materials with laser cutting machines, and the gas pressure is an extremely important factor. The auxiliary gas is ejected coaxially with the laser beam to protect the lens from contamination and blow away the slag at the bottom of the cutting area. For non-metallic materials and some metallic materials, use compressed air or inert gas to process melted and evaporated materials while suppressing excessive combustion in the cutting area.

For most metal laser cutting, active gas (as long as it is O2) is used to form an oxidative exothermic reaction with the hot metal. This part of the additional heat can increase the cutting speed by 1/3 to 1/2. When cutting thin materials at high speed, higher gas pressure is required to prevent sticking of slag on the back of the cut (hot sticky slag on the workpiece will also damage the cutting edge). When the thickness of the material increases or the cutting speed is slow, the gas pressure should be appropriately reduced. In order to prevent frosting of the plastic cutting edge, it is better to cut with a lower gas pressure

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