Laser Cutting Machine

Principle of Laser Processing Technology

Laser Processing Technology

Estimated reading time: 30 minutes

Laser is the abbreviation of English Light amplification by stimulated emission of radiation, which means “light amplification by stimulated emission of radiation”. As an important symbol of the development of science and technology in the 20th century and one of the pillars of optoelectronic technology in the modern information society, the development of laser technology and related industries has been highly valued by advanced countries. Laser processing is the most promising field of laser applications. In particular, laser welding, laser cutting, and laser cladding technologies have developed rapidly in recent years and have produced huge economic and social benefits.

Principles, characteristics, and technology of laser processing

The laser processing technology is a technology that uses the characteristics of the interaction between the laser beam and the substance to cut, weld, surface treatment, perforate, and emblem processing on materials (including metals and non-metals). As an advanced manufacturing technology, laser processing has been widely used in automotive, electronic appliances, aviation, metallurgy, machinery manufacturing, and other industrial fields. It plays an increasingly important role in improving product quality and labor productivity, achieving automation and pollution-free, and reducing material consumption. effect.

The principle of laser processing

Laser processing is a processing method in which a focused laser beam is used as a heat source to bombard the workpiece to melt metal or non-metal workpieces to form small holes, cuts, connections, cladding, etc. Laser processing is essentially a process of interaction between laser and non-transparent material. It is a quantum process in the microscopic view, and it is reflected, absorbed, heated, melted, vaporized, and other phenomena in the macroscopic view.

Under the irradiation of laser beams of different power densities, various changes occur in the surface area of the material. These changes include surface temperature rise, melting, vaporization, formation of small holes, and generation of photo-induced plasma. Figure 1.1 shows several changes in the state of the metal material under the action of laser radiation with different power densities.

Several physical changes on the surface of metal materials under the action of laser radiation
Figure 1.1. Several physical changes on the surface of metal materials under the action of laser radiatio

When the laser power density is less than 104 W/cm2, the absorption of laser energy by the metal only causes the temperature of the surface of the material to rise, but the solid phase remains unchanged. It can be used for surface heat treatment, phase change hardening, or brazing of parts.

When the laser power density is in the order of 104~106W/cm2, thermal conductivity heating is generated, and the surface layer of the material will melt. It can be used for metal surface remelting, alloying, cladding, and thermal conductivity welding (such as thin plate high-speed welding and Precision welding, etc.).

When the laser power density reaches the order of 106W/cm2, the surface of the material is irradiated by the laser beam, and the heating temperature of the laser heat source reaches the boiling point of the metal, forming a plasma vapor and violently vaporizing. Under the action of vaporization expansion pressure, the liquid surface is recessed downwards. Deep penetration small holes, at the same time, the metal vapor is ionized under the action of the laser beam to generate photo-induced plasma, which is mainly used for laser penetration welding, cutting, and drilling.

When the laser power density is greater than the order of 107 W/cm2, the photo-induced plasma will propagate against the incident direction of the laser beam, forming a plasma cloud, and the phenomenon of shielding the laser by the plasma will be used for drilling with a pulsed laser. Processing such as impact hardening.

Laser processing is the use of a high-power density laser beam to irradiate the workpiece to melt and vaporize the material to perform special processing such as perforation, cutting, and welding( see Figure 1.2.). The early condensing processing was mostly used for drilling small holes and micro-welding due to its low power. By the 1970s, with the emergence of high-power CO2 lasers, high-repetition-rate yttrium aluminum garnet (YAG) lasers, and in-depth research on laser processing mechanisms and processes, laser processing technology has made great progress, and the scope of application varies The expansion. Several kilowatts of laser processing equipment have been used for high-speed cutting, deep penetration welding, and surface treatment of various materials. Various specialized laser processing equipment is competing to appear, and combined with photoelectric tracking, computer digital control, robotics, and other technologies, greatly improving the automation level and use functions of laser processing.

Cutting sample
Figure 1.2. Cutting Sample

The laser can be interpreted as a device that converts raw energy such as electric energy, chemical energy, thermal energy, light energy, or nuclear energy into electromagnetic radiation beams of certain specific light frequencies (ultraviolet light, visible light, or infrared light). The conversion form is easy to carry out in some solid, liquid, or gaseous media. When these media are excited in the form of atoms or molecules, they produce laser beams with almost the same phase and nearly a single long beam. Due to the same phase and single wavelength, the difference angle is very small, and the distance that can be transmitted is quite long before being highly concentrated to provide functions such as welding, cutting, and cladding.

Laser processing equipment is composed of four major parts, namely laser, optical system, mechanical system, control, and detection system. The high-intensity laser beam output from the laser is focused on the workpiece through the lens, and the power density at the focal point is as high as 106~1012 W/cm2 (the temperature is as high as 10000℃), and any material will melt and vaporize instantaneously. Laser processing is to uses the thermal effect of this light energy to perform welding, drilling, and cutting of materials. The lasers commonly used for processing are mainly YAG solid-state lasers and CO2 lasers, which have the advantages of simple structure, large output power, and high energy conversion efficiency, and can be widely used for laser processing of materials.

Features of laser processing

The world’s first laser beam was produced by using a flashbulb to excite ruby crystal grains in 1960. Due to the limitation of the heat capacity of the crystal, it can only produce a very short pulse beam and the frequency is very low. Although the instantaneous pulse peak energy can be as high as 106W/cm2, it is still a low energy output.

The use of yttrium aluminum garnet crystal rods (Nd: YAG) with the number (Nd) as the excitation element can produce a continuous single-wavelength beam of 1~8Kw. The YAG laser (wavelength is 1.06 pm) can be connected to the laser processing head through a flexible optical fiber. The equipment layout is flexible and suitable for welding with a thickness of 0.5-6mm. Using CO2 laser (wavelength 1.06 pm) with CO2 as the exciter, the output energy can reach 25kW, and it can be used for single-pass full penetration welding of 2mm thick plates. It has been widely used in metal processing in the industry.

  • The light spot is small, the energy is concentrated, and the heat-affected zone is small; the laser beam is easy to focus and guide, which is convenient for automatic control.
  • It does not touch the processing workpiece, and has no pollution to the workpiece; it is not subject to electromagnetic interference and is more convenient to use than electron beam processing.
  • The processing range is wide, almost any material can be engraved and cut. High-speed engraving and cutting can be carried out according to the pattern output by the computer, and the speed of laser cutting is much faster than that of wire cutting.
  • Safe and reliable: non-contact processing is adopted, which will not cause mechanical extrusion or mechanical stress to the material section. Accurate and meticulous; machining accuracy can reach 0.1mm. Consistent effect: to ensure that the processing effect of the same batch of workpieces is almost the same.
  • The cutting seam is small; the cutting seam of laser cutting is generally 0.1~0.2mm, and the cutting surface is smooth: the cutting surface of laser cutting has no burrs. Small thermal distortion: The laser processing of laser cutting is thin, fast, and concentrated in energy. Therefore, the heat transferred to the material to be cut is small, and the deformation of the material is also very small.
  • It is suitable for the processing of large products. The mold manufacturing cost of large products is very high. Laser processing does not require any molds, and laser processing can completely avoid the collapse of the material when the material is punched and cut, which can reduce the production cost of the enterprise and improve the product. The gears.
  • Low cost: Not limited by the number of processing, laser processing is more suitable for small batch processing services.
  • Material saving: laser processing adopts computer programming, which can cut products of different shapes, which maximizes the utilization rate of materials and greatly reduces the cost of materials.

Laser processing technology

Laser technology is a comprehensive technology involving multiple disciplines such as light, mechanics, electricity, materials, and testing. Traditionally, laser processing techniques include cutting, welding, surface treatment, cladding, punching (marking), scribing, and other processing techniques. The requirements of different material processing methods on the laser power and beam quality of the laser manufacturing system are shown in Figure 1.3.

Laser welding technology

Laser welding is one of the important aspects of the application of laser processing technology. Laser radiation heats the surface of the workpiece, and the surface heat is diffused into the interior through heat conduction. By controlling the width, energy, power density, and repetition frequency of the laser pulse, the workpiece is melted to form a specific molten pool. Because of its unique advantages, it has been successfully used in the welding of small and small parts. The emergence of high-power CO2 lasers and high-power fiber lasers opened up a new field of laser welding. Deep penetration welding based on the pinhole effect has been obtained, and it has been widely used in machinery, automobile manufacturing, steel, and other industrial sectors.

Laser welding can weld difficult-to-access parts and perform non-contact long-distance welding, which has great flexibility. YAG laser technology uses optical fiber transmission technology, which makes laser welding technology more widely used. The laser beam is easy to split the beam according to time and space and can process multiple beams at the same time, which provides conditions for more precise welding. For example, it can be used for thick and thin automobile body plates, automobile parts, lithium batteries, cardiac pacemakers, sealed relays, etc. Various devices and sealed devices do not allow welding deformation and contamination.

The requirements of material processing methods for laser power and beam quality
Figure 1.3 The requirements of material processing methods for laser power and beam qualit

Laser welding technology has a molten pool purification effect, can obtain pure weld metal, and is suitable for welding between the same and dissimilar metal materials. Laser welding has high energy density, which is particularly advantageous for welding metals with a high melting point, high reflectivity, high thermal conductivity, and very different physical properties.

The main advantages of laser welding are fast speed, large penetration, small deformation, and can be welded at room temperature or under special conditions. When the laser passes through the electromagnetic field, the beam will not shift; the laser can be welded in air and certain gas environments and can weld glass or materials that are transparent to the beam. After the laser is focused, the power density is high, and the aspect ratio during welding can reach 5:1, up to 10:1, and it can weld refractory materials such as titanium and quartz, and can weld dissimilar materials with good results, such as Welding two materials with different properties, copper and tantalum, can achieve a pass rate of 100%. Micro-welding can also be performed. After the laser beam is focused, a small spot can be obtained, and it can be precisely positioned. It can be used in the assembly welding of micro and small components of mass automated production, such as integrated circuit leads, clock hairsprings, picture tube electron gun assembly, etc., Due to the use of laser welding, the production efficiency is high, the heat-affected zone is small, and the solder joints are pollution-free, which greatly improves the welding quality.

Laser cutting technology

Laser cutting is achieved by applying high power density energy generated by laser focusing. Under the control of the computer, the laser is discharged through pulses, and a controlled repetitive high-frequency pulsed laser is output to form a laser beam with a certain frequency and a certain pulse width. The pulsed laser beam is transmitted through the optical path, reflected, and focused on the surface of the processed object through the focusing lens group, forming a small, high-energy-density spot, the focus is located near the surface to be processed, and the processed material is melted or vaporized at an instant high temperature.

The high-energy laser pulse can sputter a small hole on the surface of the object in an instant. Under the control of the computer, the laser processing head and the processed material perform continuous relative movement according to the pre-drawn graphics, so that the object will be processed into the desired shape. When cutting, a stream of air coaxial with the beam is ejected from the cutting head, and the melted or vaporized material is blown away from the bottom of the incision. Compared with traditional plate processing methods, laser cutting has the advantages of good cutting quality (narrow cut width, small heat-affected zone, smooth cut), fast cutting speed, high flexibility (can cut any shape), and a wide range of material adaptability.

Laser cutting technology is widely used in the processing of metal and non-metal materials, which can greatly reduce processing time, reduce processing costs, and improve workpiece quality. Modern laser cutting technology has become the “cutting iron like mud” sword that people ideally pursue.

Taking the CO2 laser cutting machine as an example, the entire cutting device is composed of a control system, a motion system, an optical system, a water cooling system, an air protection system, etc., using advanced CNC mode to achieve multi-axis linkage and laser energy cutting without being affected by speed; The servo motor with superior performance and the transmission guiding structure can achieve good motion accuracy at high speed.

Laser cutting can be used in automobile manufacturing, computers, electromechanics, metal parts, and special materials, circular saw blades, spring washers, copper plates for electronic parts, metal mesh plates, steel pipes, Bakelite’s, aluminum alloy sheets, quartz glass, silicon Rubber, alumina ceramic sheet, titanium alloy, etc. The lasers used are YAG lasers and CO2 lasers. Pulsed lasers are suitable for metallic materials, and continuous lasers are suitable for non-metallic materials. The latter is an important application field of laser cutting technology.

Laser cladding technology

Laser cladding refers to the simultaneous melting of the cladding material and the surface layer of the substrate by laser beam irradiation on the surface of the cladding substrate in different ways, and the rapid solidification to form a melting with extremely low dilution and a metallurgical bond with the substrate. Coating, a process method to improve the wear resistance, corrosion resistance, heat resistance, oxidation resistance, and electrical characteristics of the base layer surface.

Using the high power density of the laser beam, adding self-fluxing alloy powder of specific composition (such as nickel-based, cobalt-based and iron-based alloys, etc.), forms a very thin cladding layer on the surface of the substrate to make them uniform in a molten state Spread on the surface of the part and reach a predetermined thickness, and form a good metallurgical bond with the micro-melting matrix, and there is only a small degree of dilution between each other. In the subsequent rapid solidification process, the surface of the part is completely different from the substrate. Functional cladding material layer with special properties. Laser cladding can completely change the surface properties of materials, and make the surface of low-cost materials obtain extremely high wear resistance, corrosion resistance, high-temperature resistance, and other properties.

Laser cladding can achieve the purpose of surface modification, repair, or remanufacturing. It can repair the holes and cracks on the surface of the material, restore the geometric size and performance of the worn parts, meet the requirements for the specific performance of the material surface, and save a lot of precious metals. Compared with surfacing, spraying, electroplating, and vapor deposition, laser cladding has the characteristics of low dilution rate, dense structure, and a good combination of cladding layer and substrate. It is widely used in aerospace, mold, and electromechanical industries. Currently, the lasers used in laser cladding are mainly high-power YAG lasers and CO2 lasers.

Laser heat treatment

The high-power density laser beam is used to heat the surface of the metal workpiece to achieve surface modification (that is, to improve the surface hardness, wear resistance, and corrosion resistance of the workpiece) heat treatment. The laser beam can be locally selectively hardened according to requirements, and the stress and deformation of the workpiece are small. This technology is widely used in the automotive industry, such as laser heat treatment of cylinder liners, crankshafts, piston rings, commutators, gears, and other parts, and is also widely used in the aerospace, machine tool industry, and machinery industry. The application of laser heat treatment in my country is much wider than that in foreign countries. The lasers currently used are mainly YAG lasers and CO2 lasers.

Laser heat treatment can achieve phase transformation hardening (or surface quenching, surface amorphization, surface remitting quenching), surface alloying, and other surface modification treatments on the metal surface, resulting in surface composition and structure properties that cannot be achieved by large surface quenching. Laser transformation hardening is the earliest, most studied, and most widely used process in laser heat treatment. It is suitable for most materials and different parts of parts with different shapes and can improve the wear resistance and fatigue strength of the parts. After laser heat treatment, the surface hardness of cast iron can reach more than 60HRC, and the surface hardness of medium carbon steel and high carbon steel can reach more than 70HRC, which improves the wear resistance, corrosion resistance, and oxidation resistance of the material, and extends the service life of the workpiece.

Laser annealing technology is a process of semiconductor processing, and the effect is much better than conventional heat treatment annealing. After laser annealing, the replacement rate of impurities can reach 98%~99%, which can reduce the resistivity of polysilicon by 40%~50%, which can greatly improve the integration of integrated circuits and reduce the spacing between circuit elements to 0.5μm.

Laser rapid prototyping technology

Laser rapid prototyping technology is formed by combining laser processing technology with computer numerical control technology and flexible manufacturing technology and is mostly used in mold and model industries. The lasers currently in use are mainly YAG lasers, CO2 lasers, and fiber lasers. Laser rapid prototyping technology integrates the latest achievements of laser technology, CAD/CAM technology, control technology, and material technology. According to the CAD model of the part, the photosensitive polymer material is cured layer by layer with a laser beam, and the sample is accurately stacked into a sample without molds and The tool can quickly and accurately manufacture parts with complex shapes. This technology has been widely used in aerospace, electronics, transportation vehicles, and other industrial fields.

Laser drilling technology

Laser drilling technology has the advantages of high precision, strong versatility, high efficiency, low cost, and significant comprehensive technical and economic benefits. It has become one of the key technologies in the modern manufacturing field. Before the emergence of lasers, only materials with greater hardness can be used. It is extremely difficult to drill holes in the material with less hardness, so it is extremely difficult to drill holes in the diamond with high hardness. After the advent of the laser, this type of operation is fast and safe, but the hole drilled by the laser is conical instead of the cylindrical shape of mechanical drilling, which is inconvenient in some places(see Figure 1.4).

Laser drilling technology
Figure 1.4 Laser drilling technology

Laser drilling is mainly used in aerospace, automobile manufacturing, electronic instrumentation, chemical, and other industries. The rapid development of laser drilling is mainly reflected in the output power of the YAG laser used for drilling has increased from 400W to 800W or even 1000W, and the peak power of drilling as high as 30~50kw, the pulse width used for punching is getting narrower, the repetition frequency is getting higher and higher, the laser output parameters are improved, the punching quality is improved, the punching speed is increased, and the application range of laser punching is also expanded. The relatively mature application of laser drilling in China is in the production of synthetic diamond and natural diamond drawing dies, as well as in the industries of clocks, instruments, aircraft blades, and printed circuit boards. The lasers currently used are CO2. Lasers and YAG lasers are the main ones, and excimer lasers, isotope lasers, and semiconductor pump lasers are also used.

Laser marking technology

Laser marking is a marking method that uses a high-energy-density laser beam to locally irradiate the workpiece to vaporize or change the color of the surface material, thereby leaving a permanent mark. Laser marking can produce a variety of characters, symbols, and patterns, etc., and the size of the characters can range from millimeters to micrometers, which has special significance for product anti-counterfeiting. After focusing, the extremely thin laser beam is like a tool, which can remove the surface material of the object point by point. The advanced nature of laser marking technology is that the marking process is non-contact processing, which does not produce mechanical extrusion or mechanical stress, and will not damage the processed items. The size of the focused laser beam is small, the heat-affected zone is small, and the processing is fine, which can complete the process that cannot be achieved by conventional methods.

The “tool” used in laser marking is a focused beam, no additional equipment and materials are needed. As long as the laser can work normally, it can be processed continuously for a long time. Laser marking has a fast processing speed and low cost. It is automatically controlled by a computer and does not require human intervention during production. Excimer laser marking is a new technology developed in recent years. It is especially suitable for metal marking and can achieve sub-micron marking. It has been widely used in the microelectronics industry and bioengineering.

What kind of information the laser can mark is related to the content of the computer design? As long as the artwork marking system designed by the computer can identify it, the marking machine can accurately restore the design information on a suitable carrier. Therefore, the function of the laser marking software actually determines the function of the laser marking system to a large extent. This technology has been applied in various materials and almost all industries. The lasers used include YAG lasers, CO2 lasers, and semiconductor pump lasers.

Laser surface strengthening and alloying

Laser surface strengthening is the use of high-power density laser beam heating to make the thin layer of the workpiece surface fusion and phase change, and then self-excited and rapid cooling to form a microcrystalline or amorphous structure. Laser surface alloying is to use a laser to heat the metal, alloy, or compound coated on the surface of the workpiece, and quickly melt with the base metal to form a new alloy layer or compound layer on the surface of the workpiece to achieve the purpose of surface modification of the material. You can also use a laser beam to heat the base metal and the passing gas to cause chemical metallurgical reactions (such as surface vapor deposition) to form a thin film with the desired phase structure on the metal surface to change the surface properties of the workpiece. Laser surface strengthening and alloying are suitable for parts that need to improve wear resistance, corrosion resistance, high-temperature resistance, and other properties in aerospace, weapons, nuclear industry, and automobile manufacturing.

Other

In addition to the above-mentioned laser processing technology, mature laser processing technology also includes laser etching technology, laser fine-tuning technology, laser storage technology, laser scribing technology, laser cleaning technology, laser enhanced electroplating technology, laser glazing technology, etc.

The photo etching technology is simpler than the traditional chemical etching technology, which can greatly reduce the production cost and can process 0.125~1μm wide line is suitable for the manufacture of very large-scale integrated circuits.

Laser fine-tuning technology can automatically fine-tune the specified resistance, with an accuracy of 0.01%~0.002%, which is lower in accuracy, efficiency, and cost than traditional processing methods. Laser fine-tuning includes thin film resistors (thickness of 0.01~0.64m) and thick film Fine-tuning of resistance (20-50μm in thickness), fine-tuning of capacitance, and fine-tuning of hybrid integrated circuits.

Laser storage technology uses lasers to record video, audio, text data, and computer information, which is one of the supporting technologies in the information age.

Laser scribing technology is the key technology for the production of integrated circuits. It has fine scribing, high precision (line width of 15-25μm, planting depth of 5-200μm), fast processing speed (up to 200mm/s), and yield Up to 99.5% or more.

The use of laser cleaning technology can greatly reduce the particle pollution of processed devices and improve the yield of precision devices.

Laser-enhanced electroplating technology can increase the deposition speed of metals, and the speed is 1000 times faster than that without laser irradiation. It is of great significance to the production and repair of micro-switches, precision instrument parts, microelectronic devices, and large-scale integrated circuits. Improved technology can increase the firmness of the electroplated layer by 100-1000 times.

Laser glazing technology has a promising future for material modification. Its low cost, easy control, and copying are conducive to the development of new materials. Laser glazing combined with flame spraying, plasma spraying, ion deposition, and other technologies has broad application prospects in controlling organization and improving surface wear resistance and corrosion resistance. Electronic materials, electromagnetic materials, and other electrical materials are ideally used in measuring instruments after laser glazing.

Current status and development trend of laser processing technology

After more than 30 years of development in my country, laser technology has achieved high-level scientific and technological achievements. Many have been used in production practices. The output of laser processing equipment has increased at an average annual rate of 20%, which has solved the technological transformation of traditional industries and the improvement of product quality. many questions. For example, laser wool chemical fiber technology is being promoted in large steel plants such as Baosteel and Benxi Iron and Steel, which will change the state of my country’s auto cover steel plate reliance on imports; the quality, function, and price of laser marking machines and laser welding equipment meet the needs of the domestic market, and the market share The rate is over 80%.

Current status of laser processing technology

Laser processing is the largest project in foreign laser applications, and it is also an important means of transforming traditional industries. It is mainly 1~10KW CO2 lasers, 100W to kilowatt YAG lasers, and high-power fiber lasers to realize the cutting of various materials, Welding, punching, cladding, and surface treatment, etc. According to the review and forecast of the laser market in recent years, the application of lasers takes the first place in the field of material processing, and medical lasers are the second largest application field abroad.

In the field of laser processing applications, CO2 lasers are the most widely used in cutting and welding, accounting for 70% and 20%, respectively, and surface treatment is less than 10%. The application of YAG lasers is welding, marking (50%), and cutting (15%). Mainly. In the United States and Europe, CO2 lasers account for 70% to 80%. In my country’s laser processing, cutting is mainly used for 10%, of which more than 98% of CO2 laser power is in the range of 1.5~3KW; about 15% of which are mainly surface treatment, most of which are laser surface treatment of automobile engine cylinder liners. The economic and social benefits of laser processing technology are very high, and there is a great market prospect.

In the automotive industry, laser processing technology gives full play to its advanced, fast, and flexible processing characteristics. For example, a large number of three-dimensional laser cutting machines are used in automobile prototypes and small batch production, which not only saves prototypes and tooling equipment but also greatly shortens the production cycle; the laser beam makes small holes in high-hardness materials and complex and curved surfaces, which are fast and No damage occurs; laser welding has become a standard process in the automotive industry. Toyota Motor Corporation of Japan has used laser technology for the welding of body panels, welding metal plates with different thicknesses and different surface coatings together, and then stamping.

Although laser surface treatment is not as common as welding and cutting abroad, it is still widely used in the automotive industry, such as the surface treatment of cylinder liners, crankshafts, piston rings, commutators, gears, and other parts. In industrially developed countries, laser processing technology is combined with computer numerical control technology and flexible manufacturing technology to derive laser rapid prototyping technology. This technology can not only quickly manufacture models, but also directly melt metal powders and 3D printing to make metal molds.

Figure 1.5 shows the process of using laser welding to replace resistance welding in the body assembly so that the car design can freely exert its imagination and creativity to design a unique style of car. At the same time, laser welding technology has higher efficiency than resistance spot welding, better joint performance, less material consumption, and other advantages.

Due to the advantages of laser processing technology, all European automobile manufacturers have adopted laser processing technology in large quantities without exception. For example, the German Volkswagen Company once ordered 4kw high-power YAG lasers for 260 sets, which are mainly used for body welding and parts processing. More than 400 sets of different types of high-power laser processing equipment have been installed on the production line of Bosch in Germany, which are mainly used for the processing and welding of auto parts. The breadth and depth of application of laser processing technology in automobile manufacturing have become an important symbol of the advancement of the automobile industry.

In the field of aerospace, before the 1970s, because there was no high-power continuous laser, pulsed laser welding was mainly used for spot welding of small precision parts, or welds formed by overlapping single welding points. After the 1970s, with the development of CO2 laser welding technology of several dry watts, the situation has undergone a fundamental change. Steel plates with a thickness of a few millimeters can be welded through at one time, and the resulting weld is similar to electron beam welding, showing the great potential of high-power laser welding. For example, the main reason why the empty name A80 can greatly reduce the weight of the aircraft, reduce fuel consumption, and reduce operating costs is to apply laser welding technology to the connection of the fuselage, the inner wing partition, and the stiffener (Figure 1.6), instead of The original riveting process was called a major technological revolution in the aviation manufacturing industry by the German aerospace industry.

Laser welding instead of resistance welding process
Figure 1.5 Laser welding instead of resistance welding process on body assembly

Since the 21st century, YAG lasers have played an increasingly important role in welding, cutting, drilling and marking. It is generally believed that YAG laser cutting can obtain good cutting quality and high cutting accuracy, but the cutting speed is limited. With the improvement of YAG laser output power and beam quality, YAG laser has squeezed into the kilowatt CO2, laser cutting market. YAG lasers are particularly suitable for microdevices that do not allow thermal deformation and welding contamination, such as lithium batteries, cardiac pacemakers, and sealed relays.

Comparison of riveting and laser welding structures
Figure 1.6 Comparison of riveting and laser welding structures

Fiber laser is a new type of laser device developed in recent years, and it is also one of the hotspot technologies in the field of optoelectronic information research at home and abroad. Because of their advantages in optical modes and service life, fiber lasers have become a representative of a new generation of solid-state lasers. They have been extensively studied and developed rapidly at home and abroad, and have broad application prospects.

The development trend of laser processing technology

The laser is one of the major inventions of the 20th century and has huge technological potential. Experts believe that now is the heyday of electronic technology, the protagonist is the computer, the next generation will be the era of optical technology, and the protagonist is the laser. Laser is especially suitable for material processing because of its three characteristics: unisexuality, coherence, and parallelism. Laser processing is the most promising field of laser applications, and more than 20 laser processing technologies have been developed abroad. The space control and time control of the laser are very good, and the material, shape, size, and processing environment of the processing object have great freedom, and it is especially suitable for automatic processing. The combination of the laser processing system and computer numerical control technology can form high-efficiency automatic processing equipment, which opens up broad prospects for high-quality, high-efficiency, and low-cost processing and production

The laser processing technology is one of the important supporting technologies of green manufacturing technology, which is in line with the national sustainable development strategy. The development trend of laser processing technology is mainly reflected in the following aspects.

  • In terms of material research and development, according to the types of materials for laser welding and cladding, laser welding and cladding materials of different materials are developed respectively.
  • In terms of process control, for astigmatism welding and cladding processes, the development trend is to develop an online monitoring system based on laser welding and cladding to monitor the laser welding and cladding process in real-time. Research and develop composite processes (such as laser arc composite, etc.) that are compatible with laser welding and cladding to improve the efficiency of laser welding and cladding.
  • In the management and robotization of processing systems, system integration is not only processing itself, but also real-time detection and feedback processing. With the establishment of expert systems, processing system intelligence has become an inevitable development trend. In order to improve the efficiency of laser welding, cutting, and cladding, low-cost intelligent robots have been developed and gradually popularized and applied.
  • The research of a new generation of industrial lasers is currently in a technological update period, which is marked by the development and application of diode-pumped all-solid-state lasers.

The complete set of laser processing equipment includes a laser generator, numerical control system, processing machine tool, etc., which constitute the flexible manufacturing system of laser processing. At present, the focus of laser processing technology research and development can be summarized as the following aspects

  • Numerical control and integration. Combining lasers with computer numerical control technology, advanced optical systems, and high-precision and automated workpiece positioning to form a research and production processing center has become a trend in the development of laser processing technology
  • Miniaturization and combination. The two processing methods of laser cutting and die stamping have been combined on a machine tool in foreign countries to make a laser punching machine. It has both the versatility of laser cutting and the high-speed and high-efficiency characteristics of stamping processing. Cutting complex shapes, punching, marking, scribing, and other processing.
  • High frequency and high reliability. At present, the repetition rate of YAG lasers abroad has reached 2000 times/s, and the average maintenance time of diode array pumped YAG lasers has been increased from the original several hundred hours to (1~2) million hours.
  • Use excimer laser for metal processing. This is a new subject of foreign laser processing. Excimer lasers can emit ultraviolet lasers with wavelengths of 157 to 350 nm. Most metals have low reflectivity for this laser and correspondingly high absorption rates. Therefore, this kind of laser has great application value in the field of metal processing.

Existing problems and market outlook

Main problems
  • The ability to transform scientific research results into productivity is poor, and many promising laser processing technology results stay in the prototype stage of the laboratory.
  • The core component of the laser processing system, the laser has few varieties and poor reliability. Abroad, not only diode-pumped all-solid-state lasers have been used in the production process, but also diode lasers have been used. Diode-pumped all-solid-state lasers in my country are still in the research and development stage.
  • The research and development of fine laser processing technology are relatively weak, and there is less research on the processing of ultraviolet laser.
  • The reliability, safety, maintainability, and matching of laser processing equipment are poor, and it is still difficult to meet the needs of large-scale industrial production.
Market outlook

Laser processing technology has greatly improved the level of traditional manufacturing, brought about great changes in product design, manufacturing technology, and production concepts, and triggered a revolution in manufacturing technology. Compared with the international advanced laser processing system, my country’s laser processing system has a large gap (data statistics show that it only accounts for about 2% of global sales). The main manifestations are that there are few high-end laser processing systems, the leading lasers are not shut down, and the micro-laser processing equipment has a large gap.

my country’s laser processing equipment manufacturers are developing steadily, and the domestic laser application market has a lot of room for development. In the next few years, laser processing production enterprises will have more rapid development, which is mainly due to the following aspects.

  • The state attaches great importance to it. Government departments at all levels are actively paying attention to, planning, and establishing projects. Many funds are being injected, which promotes independent innovation and technological upgrading of enterprise products.
  • The acceptance of laser processing technology in various domestic manufacturing industries can increase the technical content of their products and speed up the product upgrading. The use of advanced laser processing technology can reach the level of “agile manufacturing” and meet the market’s requirements for personalized products.
  • Gradually an industrial group of laser parts supporting enterprises has been gradually formed, and various distinctive laser processing system manufacturers have been gradually established. At present, four laser processing equipment manufacturing industrial belts have been formed, mainly distributed in Central China, the Pearl River Delta, the Yangtze River Delta, and the Yangtze River Delta. Beijing-Tianjin Rim Bohai Economically developed area.
  • The research and development of domestic leading lasers have entered the market application stage, such as high-power axial CO2 lasers, small and medium-power metal cavity RF CO2 lasers, semiconductor-pumped all-solid-state lasers, fiber lasers, as well as frequency-doubled DPL, high-power diode modules, etc. Entering the stage of commercialization, the positive development is ready, creating conditions for the application of domestic laser processing equipment.

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One thought on “Principle of Laser Processing Technology

  1. Prowell Hammis says:

    Muy buen articulo

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