When the focused laser beam hits the workpiece, the irradiated area heats up dramatically to melt or vaporise the material. Once the laser beam has penetrated the workpiece, the cutting process begins: the laser beam moves along the contour line and melts the material at the same time. A jet of air is usually used to blow the molten material away from the cut, leaving a narrow slit between the cut part and the plate holder, which is almost as wide as the focused laser beam.
Flame cutting is a standard process used when cutting mild steel, using oxygen as the cutting gas. The oxygen is pressurised to up to 6 bar and blown into the cut. There, the heated metal reacts with the oxygen: it starts to burn and oxidise. The chemical reaction releases a large amount of energy (up to five times the energy of the laser) to assist the laser beam in the cutting process.
Melt cutting is another standard process used when cutting metal. It 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 to 20 bar is blown across the cut. Argon and nitrogen are inert gases, which means that they do not react with the molten metal in the kerf and simply blow it away towards the bottom. At the same time, the inert gases protect the cutting edge from oxidation by air.
Compressed air cutting
Compressed air can also be used to cut thin sheets. Air pressurised to 5-6 bar is sufficient to blow the molten metal out of the kerf. As the air is nearly 80% nitrogen, compressed air cutting is essentially melt cutting.
If the parameters are chosen correctly, a plasma cloud will appear in the kerf of a plasma-assisted fusion cut. The plasma cloud consists of ionised metal vapour and ionised cutting gas. The plasma cloud absorbs the energy of the CO2 laser and converts it into the workpiece so that more energy is coupled to the workpiece and the material melts faster, resulting in a faster cut. For this reason, this cutting process is also called high-speed plasma cutting. The plasma cloud is in fact transparent in relation to the solid-state laser and therefore plasma-assisted fusion cutting can only be done with a CO2 laser.
Vaporised cutting vaporises the material and minimises the thermal effect on the surrounding material. This can be achieved by using a continuous CO2 laser to vaporise low heat, high absorption materials such as thin plastic films and non-melting materials such as wood, paper and foam. Ultrashort pulsed lasers allow this technology to be applied to other materials. The free electrons in the metal absorb the laser and heat up violently. The laser pulse does not react with the molten particles and plasma, the material sublimates directly and there is no time to transfer the energy as heat to the surrounding material. The picosecond pulse ablates the material with no visible thermal effect, no melting and no burr formation.
Contact: Jacky Wang
Phone: +86 14714816052
Tel: +86 14714816052
Email: [email protected]
Add: Floor 1, Shixi Industrial area, Canton, Guangdong, China. 510288