I. Overview
Laser automatic cutting equipment technology is a new development technology with extremely fast development. Compared with traditional flame cutting and plasma cutting, it has high processing precision, small thermal deformation and good cutting quality. It is a kind of occasion for high cutting requirements. The ideal cutting processing technology, the popularization and application of laser automatic cutting equipment will provide advanced technical equipment for the technological transformation of China's traditional industries, the emerging industrial field and the modernization of manufacturing. Faced with the growing market of laser automated cutting equipment applications and the new international competition, the industrialization of laser automated cutting technology needs a big development. This situation brings excellent opportunities and challenges to domestic laser-automatic cutting equipment manufacturers.
China's laser automatic cutting equipment technology industry is in a period of rapid development, and some domestic laser cutting equipment and light source technology has reached the international advanced level; until last year, China's laser industry has begun to take shape. As an advanced manufacturing technology, laser technology is increasingly intensive in all walks of life, playing an important role in the transformation and upgrading of China's manufacturing industry.
The classification of laser automatic cutting equipment is mainly distinguished by the type of light source, the power of the light source, and the cutting dimension (planar or three-dimensional). The subdivision technical indicators are cutting speed, cutting precision, driving mechanism of the motion mechanism, manual or auto focus function and work. Table size, etc.
Second, the laser source classification and its technical characteristics
At present, laser sources for laser automated cutting equipment on the market mainly include CO 2 laser, fiber laser, and YAG laser.
CO 2 laser
6微米。 The laser working material of the CO 2 laser is a CO 2 mixed gas, the main application of the laser wavelength is 10. 6μm. Since the laser has high laser conversion efficiency, and the heat generated by the laser can be quickly transmitted to the laser gain region by convection or diffusion, the average power of the laser output can be achieved at a high level (over 10,000 watts). High power laser processing requirements.
CO 2 lasers can be divided into several types: low power, medium power, and high power CO 2 lasers.
(1) Low-power (<200W) CO 2 laser applications are mainly in the electronics industry (such as resistor manufacturing, IC marking), non-metallic processing industry (bamboo wood carving, apparel, footwear, jewelry manufacturing, etc.) and some medical and research units. Used.
(2) Medium and high power (200~ 1600W) CO 2 laser application mold industry, cutting of various machine parts, automotive sheet metal cutting, sheet metal cutting of computer and electrical casing, special material cutting such as: plastic, glass, mould Non-metallic cutting.
(3) Application of high-power (>1600W) CO 2 laser High-power CO 2 laser with more than 1600W is mainly used in metal cutting, welding and surface treatment. It has gradually been used in defense, automobile and aerospace industries in advanced industrial countries. Used in some special fields.
Traditional high-power shaft fast-flow CO 2 lasers are still the mainstream configuration in high-power laser cutting equipment. Although fiber lasers have developed rapidly in recent years, CO 2 lasers still account for as much as 65% of the total.
High-power CO 2 lasers for laser processing at home and abroad are mainly cross-flow and axial-flow lasers. The beam quality of cross-flow lasers is not very good, it is multi-mode output, mainly used for heat treatment and welding. At present, China has been able to produce a variety of high-power cross-flow CO 2 laser series, which can meet the needs of domestic laser heat treatment and welding.
Axial-flow lasers: Axial-flow lasers have good beam quality and are used for fundamental mode or quasi-basic mode output. They are mainly used for laser cutting and welding. The laser cutting equipment market in China is mainly occupied by foreign axial-flow lasers. Although domestic laser manufacturers have done a lot of work on foreign axial current lasers, because the main parts still need to be imported, the price of the products is difficult to drop drastically and the penetration rate is low.
Swirl CO 2 laser: With the new rotary gas flow mode, the cyclonic CO 2 laser has the advantages of good axial beam CO 2 laser beam quality and low cross-flow CO 2 laser cost and small volume. The promotion and application of this kind of industrial processing laser will play a positive role in promoting the development and popularization of China's laser processing industry.
In the late 1960s, China began research on high-power CO 2 lasers and their applications. After more than 30 years of hard work, the production capacity of 500 ~ 10kW series products has been formed. About 10 companies and units can produce more than 500W CO 2 lasers, including Chutian, Huagong, Dazu, Nanjing Oriental, Nanjing Tong Express and Shanghai Prima. However, on the whole, Chinese lasers still have a certain distance compared with foreign countries. Most of the Chinese market uses imported products. International brands include Rofin, Trumpf, PRC, Coherent, Access, Prima, Swiss Super, Japan's Mitsubishi, Japan's Mazak and Japan's Amada.
In general, China's CO 2 laser technology has undergone years of cultivation and has developed to a certain extent. All of the high-power CO 2 lasers on most cutting machines in China still rely on imports. Compared with foreign countries, domestic high-power CO 2 lasers have a certain gap in terms of their laser quality and their measurement and control systems.
2. Fiber laser
Fiber laser cutting technology has appeared in China only in less than 5 years. The superiority of fiber laser is mainly reflected in: fiber laser is a waveguide structure with high gain, high conversion efficiency, low threshold, good output beam quality, narrow line width, structure Simple, high reliability, easy to achieve coupling with fiber, peak output power up to hundreds of kilowatts, near 1.06mm, high absorption efficiency for most materials, small size, light weight, easy to move, focused spot diameter Smaller (10 to 100 mm) enables very precise cuts, eliminating the need for post-processing steps. Through the output of the optical fiber, it is easy to cooperate with the robot to realize laser long-distance processing, and the overall photoelectric conversion efficiency is as high as 25% to 30%, which can work stably for a long time, is convenient to maintain, and has low running cost.
Although fiber laser cutting is good at cutting most materials, it cannot be used to cut acrylic or polycarbonate materials, and it can only cut wood or fiber materials in limited applications. The companies that produce fiber lasers include SPI, IPG, and domestic Ricoh lasers (owned by Huagong Laser).
3. YAG laser
The YAG laser output has a wavelength of 1. 06 mm, which is an order of magnitude smaller than the CO 2 laser wavelength of 10.06 mm. Conventional solid-state lasers are usually pumped with a high-power gas discharge lamp with a pumping efficiency of 1% to 3%. The large amount of energy emitted by the pump lamp is converted into heat energy, which not only causes the solid laser to adopt a cumbersome cooling system, but also a large amount of thermal energy causes a thermal lens effect that cannot be eliminated by the working substance, which deteriorates the beam quality. In addition, the life of the pump lamp is about 300h. The operator needs to spend a lot of time to change the lamp frequently, interrupt the system work, and greatly reduce the efficiency of the automated production line. However, if a diode-pumped solid-state laser is used, this can be well avoided. a little. YAG solid-state laser cutting machine has the characteristics of low price and good stability, but the energy efficiency is generally less than 3%. At present, the output power of the product is mostly below 600W. Because of the small output energy, it is mainly used for punching and spot welding and thin plates. Cutting. Its green laser beam can be applied in the case of pulse or continuous wave. It has short wavelength and good condensing properties. It is most effective for precision machining, especially for pulse processing under pulse. It can also be used for cutting, welding and lithography. The wavelength of YAG solid-state laser cutting machine laser is not easy to be absorbed by non-metal, so it can not cut non-metallic materials, and YAG solid-state laser cutting machine needs to solve the problem of improving the stability and life of power supply, that is, to develop large-capacity, long-life optical pump. Excitation of the light source, such as the use of a semiconductor optical pump, can greatly increase energy efficiency.
Third, the comparison of CO 2 laser cutting machine and fiber laser cutting machine
(1) As the mainstream, the traditional laser cutting and welding equipment uses CO 2 laser, which can stably cut carbon steel within 20mm, stainless steel within 10mm, and aluminum alloy below 8mm. Fiber lasers have obvious advantages when cutting thin plates within 4 mm. Due to the wavelength of solid lasers, they are of poor quality when cutting thick plates. The laser cutting machine is not omnipotent. The wavelength of the CO 2 laser is 10.6mm. The wavelength of the solid-state laser such as YAG or fiber laser is 1. 06mm. The former is more easily absorbed by non-metals and can cut wood, acrylic and PP with high quality. Non-metallic materials such as plexiglass, the latter is not easily absorbed by non-metals, so it is impossible to cut non-metallic materials, but the two lasers are not good when they encounter high-reflection materials such as copper, silver, and pure aluminum.
(2) Because the wavelengths of CO 2 and fiber laser are different by an order of magnitude, the former cannot be transmitted by optical fiber, and the latter can be transmitted by optical fiber, which greatly increases the degree of flexibility of processing. In the early days before the introduction of the fiber laser, in order to realize the three-dimensional processing, we used the optical joint technology to guide the CO 2 laser to the surface of the three-dimensional curved surface through a highly sophisticated dynamic combined mirror system to realize the three-dimensional processing of the CO 2 laser. Because the limitations of domestic precision processing technology are mainly in the hands of a handful of developed countries in Europe and America, the price is high and the maintenance requirements are high. The market share of fiber laser has gradually lost its market while gradually expanding its market share. The fiber laser can be transmitted through the optical fiber, and the degree of flexibility is unprecedentedly improved. Especially for the automotive industry, since the thin plate surface processing is basically about 1 mm, the fiber laser is matched with the same flexible robot system, and the cost is low and the number of fault points is small. The maintenance is convenient, the speed is very fast, and the market is firmly occupied by the people.
(3) The photoelectric conversion rate of fiber laser is more than 25%, and the photoelectric conversion rate of CO 2 laser is only about 10%. The advantages of fiber laser in the cost of electricity consumption and supporting cooling system are quite obvious, if the manufacturer of fiber laser is more More, the price is a little more suitable, and solve the thick plate cutting process, the threat of CO 2 laser will be huge. However, fiber laser as an emerging laser technology is far less popular than CO 2 laser. Its stability and reliability, and the convenience of after-sales service have yet to be observed in the market for a long time.
It is worth mentioning that, according to international safety standards, the laser hazard level is divided into 4 levels, CO 2 laser is the lowest level of damage, and the fiber laser is the most harmful to the human body due to its short wavelength. For safety reasons, fiber laser processing requires a fully enclosed environment.
(4) The flexible processing system of fiber lasers with robots has a long history in the automotive industry and supporting industries. In the past, it was monopolized by foreign integrators. In recent years, due to the financial crisis and the continuous improvement of production technology in the automotive industry, especially at home. High-end laser technology manufacturers, such as Huagong Laser Farley's technical research, with the support of national policies, automotive white body welding, car dashboard laser weakening, automotive airbag laser welding, auto insurance Flexible cutting of robots such as bars, doors and center pillars, laser welding of automobile bumpers, on-line welding systems for automobile exhaust pipes, and laser automatic cutting devices for automobile shifting sets.
In summary, the direction of laser applications should be that high-power CO 2 lasers are used on more stable, larger format, faster machines. For 3D surface machining up to 2mm, fiber laser is more advantageous.
Fourth, YAG laser and CO 2 laser comparison
The YAG laser output has a wavelength of 1. 06mm, which is an order of magnitude smaller than the CO 2 laser wavelength of 10.06mm, so that it has high coupling efficiency with metal and good processing performance. YAG laser can be coupled with fiber by time division and power division. The multi-channel system can easily transmit a laser beam to multiple stations or remote distance stations, which is convenient for laser processing. YAG laser can work in both pulse and continuous modes, and its pulse output can be adjusted by Q and lock. The mode technology obtains short pulse and ultrashort pulse, so that its processing range is larger than that of CO 2 laser; YAG laser has compact structure, light weight, simple and reliable use, low maintenance requirements and relatively low price, so its application prospect is promising.
The main disadvantages of YAG lasers are:
First, its conversion efficiency is low, only 1% to 3%, which is about an order of magnitude lower than the efficiency of a CO 2 laser.
Second, the YAG laser bar has an internal temperature gradient during operation, which causes thermal stress and thermal lensing, which limits the further improvement of the average power and beam quality of the YAG laser.
Third, the cost per watt of output power of a YAG laser is more expensive than a CO 2 laser.
Fourth, the output power of the current products is mostly below 600W. Because of the small output energy, it is mainly used for punching and spot welding and thin plate cutting.
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