I. Main characteristics of laser cutting
1. Laser cutting has a narrow slit and small workpiece deformation
The laser beam is focused into a very small spot so that a very high power density is achieved at the focal point. At this point the heat input from the beam far exceeds that reflected, conducted or diffused by the material, which is quickly heated to the point of vaporisation and evaporation to form a hole. As the beam moves linearly relative to the material, the holes are made to form a continuous slit of very narrow width. The cutting edge is minimally affected by the heat and there is essentially no workpiece deformation.
An auxiliary vapour suitable for the material being cut is also added to the cutting process. When cutting steel, oxygen is used as an auxiliary vapour to oxidise the material in an exothermic chemical reaction with the molten metal and to help blow away the slag in the cut. Compressed air is used for cutting plastics such as polypropylene and inert vapour is used for cutting flammable materials such as cotton and paper. The auxiliary vapour entering the nozzle also cools the focusing lens, preventing soot from entering the lens holder and contaminating the lens and causing it to overheat.
Most organic and inorganic materials can be cut by laser. In the metalworking industry, which plays a large part in the industrial manufacturing system, many metals, regardless of their hardness, can be cut without distortion. Of course, for highly reflective materials such as gold, silver, copper and aluminium alloys, which are also good conductors of heat transfer, laser cutting is difficult or even impossible.
Laser cutting is burr-free, wrinkle-free and highly accurate, which makes it superior to plasma cutting. For many mechanical and electrical manufacturing industries, because of the microcomputer program-controlled modern laser cutting system can facilitate the cutting of different shapes and sizes of workpieces, it is often more preferred than punching and moulding process; although it is still slower than mould punching, but it does not have mould consumption, no need to repair the mould, but also save time to replace the mould, thus saving processing costs, reducing production costs, so from the overall consideration is more It is more cost effective overall.
2. Laser cutting is a contactless process with high energy and controlled density
The laser beam is focused to form a very small point of action with extremely high energy and its application to cutting has a number of features.
Firstly, the laser light energy is converted into a surprising amount of heat energy kept in a very small area, providing (1) a narrow straight edge cut; (2) a minimal heat affected zone adjacent to the cut edge; and (3) very little localised distortion. Secondly, the laser beam exerts no force on the workpiece, it is a contactless cutting tool, which means (1) no mechanical deformation of the workpiece; (2) no tool wear and tear, and no talk of tool changeover; (3) no need to consider the hardness of the material being cut, i.e. the laser cutting capability is not affected by the hardness of the material being cut, any hardness can be cut. <! — Inject Script Filtered –> Once again, the laser beam is highly controllable and has a high degree of adaptability and flexibility, thus (1) it is easy to combine with automated equipment and to automate the cutting process; (2) the laser beam has unlimited profiling capabilities as there is no restriction on the workpiece to be cut; (3) in combination with a computer, the whole board can be scheduled, saving material .
3. Laser cutting offers a wide range of adaptability and flexibility
Compared to other conventional processing methods, laser cutting offers greater adaptability.
Firstly, compared to other thermal cutting methods, which also act as thermal cutting processes, other methods cannot act on a very small area as the laser beam does, resulting in wide kerfs, large heat affected zones and significant workpiece distortion. Laser can cut non-metals, while other thermal cutting methods can not.
Second, the main processes of laser cutting
1. Vapour cutting
Under the heating of a high power density laser beam, the surface temperature of the material rises to boiling point temperature so quickly that melting caused by heat conduction is avoided, so that part of the material vaporises and disappears as steam and part of the material is blown away from the bottom of the cut as an ejecta by the auxiliary gas stream.
2. Melt cutting
When the power density of the incident laser beam exceeds a certain value, the material at the point of beam irradiation opens up inside the mother and evaporates, forming a hole. Once this small hole is formed, it acts as a black body to absorb all the energy of the incident beam. The hole is surrounded by molten metal walls and an auxiliary airflow coaxial to the beam then carries the molten material around the hole. As the workpiece moves, the small hole moves across in the cutting direction in parallel to form a slit.
The laser beam continues along the front of this slit and the molten material is continuously or pulsatingly blown away from within the slit.
3. Oxidation melting cutting
If oxygen or other reactive gases are used instead, the material is ignited by the laser beam and reacts violently with the oxygen to produce another heat source, known as oxidative melting cutting.
4. Controlled fracture cutting
For brittle materials that are susceptible to thermal damage, a high-speed, controlled cut-off by heating with a laser beam is known as controlled fracture cutting. The main element of this cutting process is that the laser beam heats a small area of brittle material, causing a large thermal gradient and severe mechanical deformation in the area, leading to the formation of cracks in the material. The laser beam can guide the creation of cracks in any desired direction as long as a balanced heating gradient is maintained.