Laser cutting technology is an advanced cutting tool. Its principle is to use high power and high density laser beam to irradiate the cut material, heat it to the vaporization temperature through high temperature, form holes, and then move the laser beam continuously to complete the cutting. This cutting method is a kind of thermal cutting treatment. Laser cutting is efficient and environmentally friendly, with good cutting quality and fast speed. It can improve cutting efficiency and gradually replace the traditional tool cutting method.
However, in the process of laser cutting, there are many factors that affect the completion quality of the material to be cut. The factors that affect the cutting quality of the laser cutting machine include cutting speed, focus position, auxiliary gas, laser output power and workpiece characteristics.
1. Laser output power
The laser cutting machine generates energy from the continuous wave output laser beam. The laser power and mode selection will affect the cutting quality. In practical operation, it is usually adjusted to a higher power to meet the requirements of cutting thicker materials. At this time, the beam mode (the distribution of beam energy in the cross section) is more important. In the case of less than high power, higher power density is obtained at the focus and better cutting quality is obtained. The mode is not consistent throughout the effective working life of the laser. The condition of the optical elements, the subtle changes of the laser working gas mixture and the flow fluctuations will affect the mode mechanism.
2. Focus position adjustment
The relative position of the focus and the workpiece surface is particularly important to ensure the cutting quality. In most cases, the focus position is just on the workpiece surface or slightly below the surface when cutting. During the whole cutting process, it is an important condition to ensure that the relative position of the focus and the workpiece is constant to obtain stable cutting quality. When the focus is in a better position, the slit is smaller and the efficiency is higher. A better cutting speed can obtain better cutting results. In most applications, the beam focus is adjusted to just below the nozzle. The distance between nozzle and workpiece surface is generally about 1.5mm.
3. Cutting speed
The cutting speed of the material is proportional to the laser power density, that is, increasing the power density can improve the cutting speed. The cutting speed is inversely proportional to the density (specific gravity) and thickness of the material to be cut. When other parameters remain unchanged, the factors to improve the cutting speed are: increase the power (within a certain range, such as 500~2000W); Improve the beam mode (such as from high-order mode to low-order mode to TEM00); Reduce the size of focus spot (such as focusing with short focal length lens); Cutting materials with low initial evaporation energy (such as plastic, plexiglass, etc.); Cutting low-density materials (such as white pine); Cut thin material.
4. Auxiliary gas pressure
The use of auxiliary gas is required for the cutting of materials by laser cutting machine, and the gas pressure is a very important factor. The auxiliary gas and laser beam are coaxially sprayed to protect the lens from pollution and blow away the slag at the bottom of the cutting area. For non-metallic materials and some metallic materials, compressed air or inert gas shall be used to treat melted and evaporated materials, while inhibiting excessive combustion in the cutting area.
For most metal laser cutting machines, active gas (as long as it is O2) is used to form oxidation exothermic reaction with hot metal. This additional heat can increase the cutting speed by 1/3~1/2. When cutting thin materials at high speed, high gas pressure is required to prevent slag sticking on the back of the cut (hot slag sticking on the workpiece will also damage the cutting edge). When the material thickness increases or the cutting speed is slow, the gas pressure should be appropriately reduced. In order to prevent the plastic cutting edge from frosting, it is also better to cut at a lower gas pressure.