There are several different types of laser cutting available, including fusion cutting, oxidation cutting and scribing. Compared with other conventional cutting processes (such as mechanical cutting and waterjet cutting), each laser cutting process can produce parts with high precision and high quality edge finish, and usually has less material contamination, physical damage and waste .
Although laser cutting has certain advantages over traditional cutting methods, some manufacturing applications may present problems, such as cutting reflective materials or materials that require secondary processing and finishing. The requirements and specifications required for a particular cutting application (for example, materials and their properties, energy consumption and power consumption limits, secondary finishing, etc.) help determine the type of cutting process most suitable for use.
Although each cutting process has its advantages and disadvantages, this article focuses on laser cutting, and outlines the basic knowledge of the laser cutting process and the necessary components and mechanical structure of the laser cutting machine. In addition, this article discusses various laser cutting methods and applications, the advantages and limitations of this method, and the comparison between laser cutting and other types of cutting methods.
Laser cutting machine and process
Laser cutting is a non-contact manufacturing process based on heat, suitable for metal and non-metal materials. In order to make the laser cutting process run smoothly and with the best capacity, several factors should be considered, such as the configuration and settings of the laser cutting machine, the material to be cut and its performance, and the type of laser and auxiliary gas used.
Overview of laser machine parts and mechanics
Compared with mechanical cutting using cutting tools and power-driven equipment and water jet cutting using pressurized water and abrasives, laser cutting uses a laser cutting machine for cutting, engraving and marking. Although laser cutting machines vary by model and application, typical settings include laser resonator components, mirrors, and laser cutting heads, which include laser focusing lenses, pressurized gas components, and nozzles. The basic laser cutting process includes the following stages:
Local heating and melting
Each stage is an indispensable part of the laser cutting process, and if executed correctly, precise cutting can be performed.
The term “laser” comes from the acronym “laser” or “optical amplification by stimulated radiation”. Essentially, this acronym summarizes the basic principles of laser generation-stimulation and amplification. Together with these principles, the laser resonator uses the processes of spontaneous emission and stimulated emission to generate a high-intensity beam (ie, laser beam) that is spatially and spectrally coherent.
The laser resonator contains an active laser medium (for example, CO2, Nd:YAG, etc.) whose electrons are excited by an external energy source such as a flash lamp or an electric arc. When the medium receives and absorbs energy, its atoms undergo a process called spontaneous emission. In this process, the energy absorbed by the atom causes the atom’s electrons to briefly jump to a higher energy level and then return to its ground state. After the electron returns to the ground state, the atom emits a photon.
The photons generated by spontaneous emission propagate in a medium contained in a laser resonator cavity between two mirrors. One mirror is reflective to keep the photons propagating in the medium so they continue to propagate stimulated emission, while the other mirror is partially transmissive to allow some photons to escape. Stimulated emission is the process by which photons (that is, incident photons) excite atoms that are already at a higher energy level. This interaction forces the excited atom to drop to its ground state by emitting a second photon of the same fixed wavelength or coherent with the incident photon.
The process of one photon propagating the emission of another photon amplifies the intensity and intensity of the beam. Therefore, the stimulated emission of photons (a type of electromagnetic radiation) causes light amplification. In other words, light is amplified by stimulated radiation emission. The improperly aligned photons in the resonator pass through the partial transmission mirror without being reflected into the medium, thereby generating the initial laser beam. Once the light beam is generated, it enters the laser cutting head and is guided by the mirror to the focusing lens.