Lasers are an effective tool for micromachining applications, where lasers can converge on a tiny target area and achieve a "cold processing" effect. The interaction between the laser and the material in the target area will be controlled by several parameters, such as wavelength, pulse energy and pulse width, etc. The combination of parameters determines the peak energy density of the pulse. Different combinations of parameters can produce the processing conditions required for marking, cutting, piercing, annealing, hardening and other operations.
To improve the output power of pulsed lasers, increase energy density and control thermal effects, the industry has developed a variety of modulation technologies, mainly including Q tuning technology, mode-locking technology, tunable technology, chirp pulse amplification technology (also known as CPA technology) and master oscillation power amplification technology (also known as MOPA technology), etc. The details are as follows:
1. Tuning Q technology works on the principle that after the particle number inversion state of the working material is formed and does not make it produce laser oscillation, when the particle number accumulates to a sufficiently high level, the switch is suddenly turned on instantaneously, so that very strong laser oscillation and high power, narrow pulse width pulse laser output can be formed in a relatively short period of time;
2. Mode-locking technology means that there is a definite phase difference between different longitudinal modes in the resonant cavity, thus obtaining a series of equally spaced laser ultrashort pulse sequences in time, which, together with special fast optical switching technology, can further select a single ultrashort laser pulse from the pulse sequence;
3. Tunable technology refers to continuously controllable output wavelength within a certain range. At present, the laser crystal (solid-state laser gain medium) has reached hundreds of types, such as sapphire, YAG crystal, etc.. Solid-state laser frequency doubling technology is the most mature, the optical band to achieve full coverage of the ultraviolet to infrared, laying a solid foundation for laser wavelength tunable;
4. CPA technology refers to the use of a broadener to broaden the femtosecond pulse in the time domain to become a long pulse of several hundred picoseconds or nanoseconds, after multi-stage amplification to fully extract the energy stored in the gain medium, and then use a pulse width compressor with opposite dispersion to compress the long pulse to a value close to its initial pulse width;
5. MOPA technology is the seed signal light and pump light with high beam quality, coupled into the double-clad fiber in a certain way for amplification, thus achieving high power amplification of the seed light source. The MOPA structure of the laser is the optimal way to solve the problem of ultrafast lasers with both high peak power and high beam quality.
The choice of laser for micromachining depends on many factors, including material properties, processing shape, and required accuracy. To meet the increasingly stringent accuracy requirements for micromachining, short wavelength, narrow pulse width, and high power will be the main trends in laser technology for micromachining applications.
Laser processing characteristics and micro processing applications
Laser processing is the industrial application of laser technology, focusing a certain power laser on the object to be processed, so that the laser interacts with the object and heats, melts or vaporizes the processed material to achieve the processing purpose. Laser processing is a typical non-contact processing, compared with other processing methods have less follow-up process, good controllability, easy integration, high processing efficiency, low material loss, low environmental pollution, high flexibility, high quality and other significant advantages.
In recent years, laser processing has been replacing traditional processing methods, and the laser industry based on lasers has developed rapidly and is now widely used in industrial manufacturing, communications, information processing,and education and scientific research, forming an industrial chain across the world, and the maturity and depth of industrial division of labor has been increasing. With the future development of application products to ultra-precise and ultra-micro direction, the application of laser in the field of micro-processing will become more and more extensive.
Laser Cutting
Working Principle: Using a focused high power density laser beam to irradiate the workpiece, the irradiated material rapidly melts, vaporizes, ablates or reaches the ignition point, while the molten material is blown away with the high-speed airflow coaxial to the beam, thus cutting the workpiece.
Application areas and features: fast cutting speed, smooth and beautiful surface, one-time processing, small deformation of the workpiece, no tool wear, small cleaning pollution, can process metal, non-metal and non-metal composite materials, leather, wood, fiber, etc. Suitable for car body thick and thin plates, automotive parts, science batteries, pacemakers, sealed relays and other sealed devices, as well as the fine processing of winter devices that do not allow welding pollution and deformation Laser Welding
Laser welding
Working Principle: Using high energy density laser beam radiation to heat the surface of the workpiece, the surface heat spreads to the inside through heat conduction. By controlling the parameters of laser pulse width, energy, peak power and repetition frequency, the workpiece melts and a specific melt pool is formed.
Application areas and characteristics: small weldability, not affected by magnetic field, small space limitation, no electrode pollution, suitable for automatic high-speed welding, can weld metals with different properties, can work in closed space, suitable for circular saw blades, acrylic, spring gaskets, copper plates for electronic parts, some metal mesh plates, iron plates, steel plates, phosphor bronze, bakelite plates, thin aluminum alloys, quartz glass, silicone rubber, below 1mm Alumina ceramic sheet, iron alloy used inindustry, etc.
Laser Marking
Working Principle: Using high energy density laser to irradiate the workpiece locally, the surface material vaporizes or undergoes a chemical reaction of color change, thus leaving a permanent mark.
Application areas and features: non-contact processing, can be marked on any shaped surface, the workpiece will not be deformed and produce internal stress, high processing accuracy, fast processing speed, clean and environmentally friendly, low cost, suitable for metal, plastic, glass, ceramics, wood, leather and other materials marking.
Laser engraving
Working principle: laser irradiation of the material surface, the material absorbs energy and melts or vaporizes instantly, forming an engraved line.
Application areas and features: automatic number skipping, small heat-affected area, fine lines, cleaning and wear resistance, environmental protection and energy saving, material saving, can be used for etching on wood products, organic glass, metal plates, glass, stone, crystal, paper, two-color plates, aluminum oxide, leather, resin and other materials.
Laser surface treatment
Working principle: Using laser to heat the surface of metal materials to achieve surface heat treatment.
Application areas and features: fast processing speed, small part deformation, precise processing, to achieve the treatment effect of automatic quenching, suitable for heat treatment of cylinder liners, crankshafts, piston rings, commutators, gears and other automotive parts, but also in the aerospace, machine tool industry and other fields are widely used.
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