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Laser cutting
Laser cutting
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Laser cutting is a process that utilizes a high-powered beam focused to a small spot to , melt, vaporize, or blow away from a workpiece, enabling precise cuts in sheets or plates of metals, plastics, wood, and other substances. The process typically involves directing the via computer numerical control (CNC) systems, often assisted by a gas jet to remove debris and enhance cut quality. Developed from foundational laser technology invented in 1960 by , laser cutting emerged in the mid-1960s with the creation of the CO2 laser by Kumar Patel in 1964, followed by the first industrial laser application in 1965, when used a to drill holes in diamond dies. By the 1970s, commercial laser cutting machines became available, revolutionizing precision fabrication in industries such as and automotive . Today, advancements like fiber lasers, introduced in the 1960s but refined in the 2000s, have improved efficiency and enabled cutting of thicker materials up to 50 mm or more in mild steel, depending on laser power. The core mechanism of laser cutting begins with the generation of a beam—commonly using CO2 lasers (wavelength 10,600 nm) for non-metals and organics, fiber lasers for reflective metals, or Nd:YAG lasers ( 1,064 nm) for high-precision tasks—followed by amplification, beam steering via mirrors, and focusing through lenses to achieve power densities exceeding 10^6 W/cm². Common techniques include fusion cutting (melting with ), vaporization cutting (direct evaporation), and reactive cutting (oxidation for metals like ), each optimized for material type and thickness. Suitable materials encompass acrylic, mild , , aluminum, , , and cork, though hazards like toxic fumes from PVC or ABS limit their use. Key advantages of laser cutting include exceptional precision with tolerances as fine as 0.1 , high-speed operation for complex geometries, and automation that reduces labor while minimizing material waste through kerf widths under 0.5 . However, it requires significant electrical power, generates hazardous fumes necessitating ventilation, and involves high initial costs for and . Applications span industrial sectors, including fabrication for automotive parts, components, prototyping in , and custom on consumer goods.

Fundamentals

Process Description

Laser cutting is a thermal subtractive process that employs a high-powered beam to precisely remove from a workpiece, typically or non-metals, by melting, vaporizing, or burning it away. The basic setup includes a source that generates the beam, a beam delivery such as mirrors or fiber to direct the light, focusing like lenses to concentrate the energy, and a workpiece positioning often controlled by computer numerical control (CNC) for accurate path following. The process begins with the generation of a coherent beam from the source, which is then directed and focused through to form a high-intensity spot on the material surface, typically 0.1-0.3 mm in diameter, achieving power densities sufficient to rapidly heat the material. As the focused beam interacts with the workpiece, it causes localized heating that melts or vaporizes the material in the beam path, creating a narrow cut known as a kerf. An assist gas, delivered through a coaxial with the beam, plays a crucial role by ejecting the molten or vaporized debris from the kerf, preventing re-deposition and ensuring clean edges; inert gases like are used for oxidation-free cuts on materials such as , while reactive gases like oxygen enhance cutting efficiency on carbon steels through exothermic oxidation. For cuts starting away from the material edge, a piercing step initiates the process by creating an entry hole; this involves pulsing the at high power to penetrate the material, with typical durations ranging from 0.5 to 15 seconds depending on thickness and type—for instance, 5-15 seconds for 0.5-inch (13 mm) . Once pierced, the beam follows the programmed contour at controlled speeds, with the assist gas maintaining cut integrity throughout. The ensures the relative motion between the beam and workpiece, completing the cut without mechanical contact.

Physical Principles

Laser cutting relies on the absorption of laser energy by the target material, which initiates a series of thermal processes leading to heating, , or . When a focused beam irradiates the material surface, photons are absorbed according to the Beer-Lambert law, where the intensity decreases exponentially with depth: I(z)=I0eαzI(z) = I_0 e^{-\alpha z}, with α\alpha being the absorption coefficient and the absorption depth δ=1/α\delta = 1/\alpha typically on the order of 10 nm for metals in the range, though it varies with and material properties. This absorption converts optical energy into , raising the local temperature rapidly; for sufficient energy input, the material reaches (around 1-10 J/cm² fluence for metals) or thresholds, depending on the and material's such as bandgap and electronic structure. The input QQ delivered to the material is approximated by Q=PtηQ = P \cdot t \cdot \eta, where PP is the laser power, tt is the exposure time, and η\eta is the absorption efficiency, which typically ranges from 20% to 90% depending on the material and processing conditions—lower for polished metals at wavelengths due to high reflectivity, but higher for roughened surfaces or non-metals. This absorbed energy drives phase changes, with volumetric heating modeled by the ρcpTt(kT)=Q(x,t)\rho c_p \frac{\partial T}{\partial t} - \nabla \cdot (k \nabla T) = Q(x,t), incorporating ρ\rho, specific heat cpc_p, thermal conductivity kk, and the source term Q(x,t)Q(x,t). Thermal effects play a central role in the cutting process, including heat conduction that determines the affected zone size via the thermal diffusion length lTDτl_T \approx \sqrt{D \tau}
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