CO2 laser cutting technology has found widespread applications in industrial production, particularly demonstrating immense potential in high-speed cutting and the processing of thick steel plates. The four primary laser cutting processes include melting cutting, vaporization cutting, oxidation melting, and controlled fracture. Let’s delve into the principles and characteristics of each of these processes in the context of CO2 laser cutting machine.
Four Process Principles of CO2 Laser Cutting Machine
Melting cutting involves heating the material with an incident laser beam. When the power density of the laser beam exceeds a certain threshold, the irradiated area of the material begins to evaporate internally, forming small holes. These holes further absorb the energy of the laser beam, melting the surrounding metal walls. Simultaneously, an auxiliary airflow, coaxial with the beam, carries away the molten material around the holes. As the workpiece moves, a cut is formed on the metal surface.
Vaporization cutting requires a higher laser beam power than melting cutting. Under such a beam, the material is heated directly to the boiling point without melting. This allows the material to disappear in a vapor state, with the vapor carrying away molten particles and flushing debris, creating holes. Approximately 40% of the material turns into vapor during the vaporization process, while the remaining 60% is expelled as molten droplets, blown away from the bottom of the cut. This process is effective for non-meltable materials such as wood and carbon materials.
Oxidation melting employs active gases like oxygen as auxiliary airflow. During cutting, the material surface is heated to the ignition point under the laser cutter’s beam, triggering a vigorous combustion reaction with oxygen, releasing a considerable amount of heat. This heat heats the material, creating small holes filled with steam and melting the metal walls surrounding the holes.
The burning rate of metal in oxygen is controlled by the transfer of the burning substance to molten slag. The speed at which oxygen diffuses through the molten slag to the ignition front directly determines the burning rate. A higher oxygen flow rate leads to more intense combustion and faster removal of molten slag, enabling higher cutting speeds. However, an excessively high oxygen flow rate may cause rapid cooling of reaction products, i.e., metal oxides, at the cut exit, adversely affecting cutting quality.
In this cutting process, metal melting has two heat sources: the heat generated by the laser cutting machine‘s laser irradiation and the heat produced by the chemical reaction between oxygen and metal. It is estimated that about 60% of the total energy required for cutting steel is released through oxidation reactions. Therefore, precise calculations are essential for the oxygen combustion rate and the laser beam’s movement speed to achieve perfect coordination. If the oxygen combustion rate exceeds the laser beam’s movement speed, the cut may appear wide and rough, while a faster laser beam may result in a narrow and smooth cut.
Controlled fracture involves heating the material with a laser beam to achieve rapid and controlled cutting. This process is highly effective for brittle materials susceptible to thermal damage. The specific procedure involves heating a small area of the brittle material with a laser beam, inducing a large thermal gradient and severe mechanical deformation, leading to the formation of cracks. As long as a balanced heating gradient is maintained, the laser beam can guide the cracks to form in any desired direction.
It’s important to note that controlled fracture cutting is not suitable for cutting sharp angles and corner cuts. Successfully achieving cuts in extra-large enclosed shapes is also challenging. Controlled fracture cutting is fast, requiring moderate power. Excessive power may cause surface melting on the workpiece, compromising the cut edge. The primary control parameters are laser power and spot size.
The four distinct process principles of CO2 laser cutting technology offer a comprehensive toolkit for various industrial applications, demonstrating versatility, precision, and efficiency in the ever-evolving landscape of manufacturing.