Blog sharing 2019-07-02
Laser cutting has been around since the 1960s, but is now relevant due to its increasing use in industrial processes. This non-contact process uses a constant beam of light to generate heat and pressure and then accurately reshapes/distorts the material as it moves over the surface of the material. Laser technology has many functions, including cutting, drilling and engraving, depending on the strength of the laser, the main constituent materials used in the laser beam and the materials it acts on. Laser cutting is one of the most important processes for making sheet metal parts.
Each laser provides continuous wavelengths for a variety of applications. There are three types of lasers: CO2 (gas laser), fiber laser and Nd:YAG or Nd:YVO (vanadate crystal laser). Each uses a different base material, electrically energized with a gas mixture or passed through a physical diode.
The CO2 laser generates electricity by generating a beam of light through a tube filled with a gas mixture. These tubes have mirrors on both ends. One of the mirrors is completely reflective and the other is partial, allowing some light to pass. The gas mixture is typically carbon dioxide, nitrogen, hydrogen and helium. CO2 lasers produce invisible light in the far infrared range of the spectrum.
For industrial machines, the most powerful CO2 lasers can reach multiple kilowatts, but these are exceptions. A typical processed CO2 laser has a power of 25 to 100 watts and a wavelength of 10.6 microns.
This type of laser is most commonly used for wood or paper (and its derivatives), polymethyl methacrylate and other acrylic plastics. It is also suitable for leather, fabrics, wallpapers and similar products. It is also used to process foods such as cheese, chestnuts and various plants.
CO2 lasers are usually best suited for non-metallic materials, although they can process certain metals. It can usually cut aluminum sheets and other non-ferrous metal sheets. One can increase the power of the CO2 beam by increasing the oxygen content, but this can be risky for inexperienced hands or machines that are not suitable for such reinforcement.
This type of machine is part of a solid state laser set and uses a seed laser. They use specially designed glass fibers to amplify the beams, which get energy from the pump diodes. Their typical wavelength is 1.064 microns, resulting in a very small focal diameter. They are also often the most expensive of the various laser cutting devices.
Fiber lasers are typically maintenance-free and have a lifetime of at least 25,000 laser hours. Therefore, fiber lasers have a longer life cycle than the other two types, and they can produce a strong and stable beam. They can manage 100 times more intensity than CO2 lasers with the same average power. Fiber lasers can be continuous beams, quasi-pulsed or pulsed to give them different functions. One subtype of fiber laser system is MOPA, whose pulse duration is adjustable. This makes the MOPA laser one of the most flexible lasers for a variety of applications.
Fiber lasers are best suited for metal marking through annealing, metal engraving and marking thermoplastics. It is suitable for metals, alloys and non-metals, even glass, wood and plastic. Fiber lasers, depending on the power, can be very versatile and handle a large number of different materials. Fiber lasers are the ideal solution when using thin materials. However, for materials over 20 mm, the situation is less severe, although more expensive fiber lasers of more than 6 kW can be used to solve this problem.
Nd:YAG / Nd:YVO Lasers
The crystal laser cutting process may be nd:YAG (yttrium-doped yttrium aluminum garnet), but more commonly they tend to use nd:YVO (yttrium-doped yttrium orthovanadate, YVO4) crystals. These devices have extremely high cutting capabilities. The disadvantages of these machines are that they are expensive, not only because of their initial price, but also because their life expectancy is 8,000 to 15,000 hours (Nd: YVO4 usually has a lower life) and the pump diode can purify very high prices.
With a wavelength of 1.064 microns, these lasers are suitable for a variety of applications in medical, dental, military and manufacturing applications. When comparing two Nd:YVOs, it exhibits higher pump absorption and gain, wider bandwidth, wider pump wavelength range, shorter upper life, higher refractive index and lower thermal conductivity. In terms of continuous operation, Nd:YVO has a performance level similar to Nd:YAG in general at medium or high power. However, Nd:YVO does not allow pulse energy to be as high as Nd:YAG, and laser lifetime lasts for a short period of time.
These can be used with metals (coated and uncoated) and non-metallic (including plastic). In some cases, it can even process some ceramics. The Nd:YVO4 crystal combines a high NLO coefficient crystal (LBO, BBO or KTP) to shift the output from near-infrared to green, blue or even ultraviolet, giving it a number of different functions.
Due to their similar size, the ruthenium, osmium or ion can be replaced by laser-active rare earth ions without strongly affecting the lattice structure required to produce the beam. This preserves the high thermal conductivity of the doped material.