Laser cutting was first used in the 1970s. In modern industrial production, laser cutting is more widely used in sheet metal, plastic, glass, ceramic, semiconductor and textile, wood and paper and other materials processing.In the next few years, the application of laser cutting in the field of precision machining and micromachining will also gain substantial growth. Laser cutting When a focused laser beam hits a workpiece, the irradiated area heats up sharply to melt or vaporize the material. Once the laser beam penetrates the workpiece, the cutting process begins: the laser beam moves along the contour while melting the material. A jet of air is usually used to blow the melt away from the cut, leaving a narrow gap between the cut section and the plate holder that is nearly as wide as the focused laser beam. Flame cutting Oxygen cutting is a standard process used when cutting mild steel, using oxygen as the cutting gas. Oxygen is pressurized up to 6 bar and blown into the incision. There, the heated metal reacts with oxygen: it begins to burn and oxidize. The chemical reaction releases a large amount of energy (up to five times of the laser energy) to assist the laser beam cutting. Melt cutting Fusion cutting is another standard process used when cutting metal. Can also be used to cut other fusible materials such as ceramics. Nitrogen or argon is used as the cutting gas, and a gas pressure of 2-20 bar is blown through the incision. Argon and nitrogen are inert gases, which means they don't react with the molten metal in the cut, just blowing them away to the bottom. At the same time, the inert gas can protect the cutting edge from being oxidized by the air. Compressed air cutting Compressed air can also be used to cut thin sheets. Air pressurized to 5-6 bar is enough to blow away the molten metal in the cut. Since nearly 80% of the air is nitrogen, compressed air cutting is basically fusion cutting. Plasma assisted cutting If the parameters are selected properly, plasma clouds will appear in the plasma-assisted melting cutting cuts. The plasma cloud consists of ionized metal vapor and ionized cutting gas. The plasma cloud absorbs the energy of the CO2 laser and converts it into the workpiece, so that more energy is coupled into the workpiece and the material melts faster, resulting in faster cutting. Therefore, this cutting process is also called high-speed plasma cutting. The plasma cloud is virtually transparent to the solid-state laser, so plasma-assisted melting cutting can only be done with CO2 lasers. Gasification cutting Evaporation cutting vaporizes the material, minimizing thermal effects on the surrounding material. This can be achieved with continuous CO2 laser processing by evaporating low-heat, high-absorbing materials such as thin plastic films as well as non-melting materials such as wood, paper, and foam. Ultrashort pulsed lasers allow the technology to be applied to other materials. Free electrons in the metal absorb the laser light and heat up violently. The laser pulses do not react with the molten particles and plasma, and the material sublimates directly, leaving no time to transfer the energy to the surrounding material in the form of heat. Picosecond pulses ablate the material without significant thermal effects, without melting and burr formation. gas cutting Parameters: Adjust the machining process Many parameters affect the laser cutting process, some of which depend on the technical performance of the laser and machine tool, while others are variable. Degree of polarization The degree of polarization indicates what percentage of the laser light is converted. A typical degree of polarization is generally around 90%. This is enough for high quality cuts. Focus diameter The focal diameter affects the width of the incision, and the focal diameter can be changed by changing the focal length of the focusing mirror. A smaller focal diameter means a narrower incision. Focus position The focus position determines the beam diameter and power density on the workpiece surface and the shape of the notch. Laser power The laser power should be matched to the type of processing, type of material and thickness. The power must be high enough that the power density on the workpiece exceeds the machining threshold. Operating mode Continuous mode is mainly used for cutting standard profiles of metal and plastic in millimeter to centimeter sizes. In order to melt the perforations or produce precise contours, low-frequency pulsed lasers are used. Cutting speed Laser power and cutting speed must match each other. Cutting speeds that are too fast or too slow can lead to increased roughness and burr formation. Nozzle diameter The diameter of the nozzle determines the flow rate and shape of the gas flow from the nozzle. The thicker the material, the larger the diameter of the gas jet, and the correspondingly larger diameter of the nozzle orifice. Gas Purity and Barometric Pressure Oxygen and nitrogen are often used as cutting gases. The purity and pressure of the gas affect the cutting effect. When using oxygen flame cutting, the gas purity needs to be 99.95 %. The thicker the steel plate, the lower the gas pressure used. Gas purity needs to be 99.995 % (ideally 99.999 %) when melt-cutting with nitrogen, and higher gas pressures are required for melt-cutting thick steel. Technical Data Sheet In the early days of laser cutting, users had to decide the setting of processing parameters by themselves through trial operation. Now, mature machining parameters are stored in the control unit of the cutting system. For each material type and thickness, there is corresponding data. The technical data sheet enables smooth operation of laser cutting equipment even for those unfamiliar with this technology. Laser cutting quality evaluation factors There are many criteria for judging the edge quality of laser cutting. Criteria such as burr forms, depressions, and lines can be judged with the naked eye; verticality, roughness, and incision width need to be measured with special instruments. Material deposition, corrosion, heat-affected zone and deformation are also important factors in measuring the quality of laser cutting. evaluation factor The continued success of laser cutting is beyond the reach of most other processes. This trend continues today. In the future, the application prospect of laser cutting will also become more and more broad. Tianhong laser cutting machine is widely used various industries, mostly in sheet metal processing.
