I. Principle of Laser Cutting
Laser cutting is a thermal cutting technology that uses a high-power-density laser beam to process materials. Its core principle is: through an optical system, the laser beam emitted by the laser is focused into an extremely small spot (diameter can be 0.1-0.3mm), achieving a power density at the focal point as high as 10⁴~10⁵ W/cm². When this high-energy beam strikes the workpiece surface, the material is heated to its melting or vaporization point in an extremely short time. Simultaneously, a high-speed auxiliary gas jet (e.g., oxygen, nitrogen) coaxial with the beam blows away the molten or vaporized material from the kerf, thus achieving the cut.
The laser cutting process primarily occurs at the ablation front, the material surface at the end of the cut. Laser energy is absorbed here; part of it heats and melts the material, while the other part may be reflected or conducted away. The material's absorption rate of the laser is a key factor determining cutting efficiency, influenced by various factors including the laser's polarization, mode, convergence angle, and the material's properties and surface condition.
II. Classification of Laser Cutting
Based on the auxiliary gas used and the working mechanism, laser cutting is mainly divided into the following types:
Laser Vaporization Cutting: Uses a high-energy-density laser beam to instantly raise the material to its boiling point for vaporization, while some melt is blown away by the gas jet. This method requires very high power and is mainly used for very thin metals and non-metals (e.g., wood, plastic, paper).
Laser Melt Cutting: The laser melts the material, and a high-pressure inert gas (e.g., nitrogen, argon) blows the molten material out of the kerf. This process requires only one-tenth the energy of vaporization cutting and is primarily used for difficult-to-oxidize or reactive metals like stainless steel, titanium, and aluminum alloys.
Laser Oxygen-Assisted Cutting: Similar in principle to oxy-acetylene cutting. It uses oxygen as the auxiliary gas, which reacts exothermically with the hot metal, providing additional cutting energy significantly boosting cutting speed and thickness. This method is widely used for cutting easily oxidized metals like carbon steel.
Controlled Fracture Cutting: A laser beam creates a groove on the surface of a brittle material, and thermal stress guides the material to crack along a predetermined path. This method is fast and requires low power, used for cutting brittle materials like glass and ceramics, but is unsuitable for sharp corners or complex shapes.
III. Technical Characteristics of Laser Cutting
Compared to other thermal cutting methods (e.g., plasma, oxy-acetylene), laser cutting offers significant advantages:
High Cutting Quality: Due to the small laser spot, the kerf is narrow (typically 0.1-0.3mm). Cutting precision can reach ±0.05mm, with a smooth, low-roughness surface (Ra 12.5-25μm). The heat-affected zone is minimal, and workpiece deformation is small, often eliminating the need for post-processing.
High Efficiency: Laser cutting is fast. For example, cutting 2mm thick mild steel with a 1.2kW laser can achieve speeds of 6m/min.
Non-Contact Processing: The laser head does not physically contact the workpiece, resulting in no tool wear, no mechanical stress, and minimal risk of workpiece deformation, making it suitable for thin and easily deformed materials.
High Flexibility: Controlled by CNC programming, it can quickly cut any complex 2D or 3D shape without changing molds, offering strong adaptability for small-batch, multi-variety customized production.
Wide Material Applicability: It can cut almost all materials, including metals (carbon steel, stainless steel, aluminum, titanium, etc.), non-metals (plastics, wood, leather, glass, etc.), and composites.
Clean and Environmentally Friendly: The process features low noise, low vibration, and minimal pollution, improving the working environment.
Laser cutting also has limitations, such as high initial equipment investment, limited capability for cutting medium-to-thick plates due to laser power constraints, and a significant decrease in cutting speed as plate thickness increases.
IV. Application Fields of Laser Cutting
Laser cutting is one of the most widely used laser processing technologies in industrial manufacturing, accounting for about 60% of material laser processing applications. Its applications span numerous industries:
Metalworking & Manufacturing: Widely used in automotive, aerospace, heavy machinery, electrical manufacturing, and medical devices for cutting various metal sheets, pipes, and components.
Non-Metal Processing: Used in signage, advertising, packaging, printing, textiles, and apparel for cutting wood, acrylic, fabric, leather, paper, and plastic sheets.
Precision & Specialized Parts: Cutting components like oil well screen pipes, printing die boards, electronic components, precision shims, and solder tabs, meeting requirements for high precision and narrow kerfs.
3D Cutting: Using industrial robots or 3D laser cutting systems for efficient cutting of complex spatial curves, such as car roof windows and body panels.
V. Laser Cutting Characteristics of Different Metals
Carbon Steel: Cut with oxygen assist, capable of cutting plates up to 25mm thick, with kerf widths as narrow as 0.1mm for thin sheets.
Stainless Steel: Using nitrogen assist yields a clean, oxide-free, burr-free edge, crucial for parts requiring high corrosion resistance.
Aluminum & Alloys: Cut via melt cutting mechanism, requiring high-power lasers. Applying a surface absorption layer can improve cutting speed. Pure aluminum is difficult to cut and requires anti-reflection devices.
Copper & Alloys: Pure copper is highly reflective and difficult to cut with CO₂ lasers; brass can be cut with higher power lasers and oxygen or air.
Titanium & Alloys: High absorption rate for lasers, resulting in good cut quality, but using oxygen can cause a violent reaction, leading to an oxide layer.
