Jun 23, 2020
Laser processing is the most advanced processing technology, which mainly uses high-efficiency laser to carve and cut materials. The main equipment includes computer and laser cutting (carving) machine. The process of using laser cutting and carving is very simple, just like using computer and printer to print on paper, and using a variety of graphic processing software (CAD, circuitcam, CorelDRAW, etc.) for graphic design After that, the graphics are transferred to the laser cutting (carving) machine, which can easily cut (carve) the graphics to the surface of any material and cut the edges according to the design requirements.
Since the invention of the ruby laser in Bell Laboratories in 1960, the laser has been gradually applied to audio-visual equipment, ranging, medical equipment, processing, and other fields.
In the field of laser processing, although the price of laser transmitter is very expensive (hundreds of thousands to millions), but because laser processing has the advantages that traditional processing can not match, laser processing has accounted for more than 50% of the processing industry in the United States, Italy, Germany, and other countries.
The laser beam can be focused to a very small size, so it is particularly suitable for precision machining. According to the size of the processed materials and the accuracy requirements of the processing, the laser processing technology is divided into three levels:
(1) The laser processing technology of large-scale materials, with thick plates (several millimeters to dozens of millimeters) as the main object, its processing accuracy is generally in millimeter or submillimeter level;
(2) The precision laser processing technology takes the thin plate (0.1-1.0mm) as the main processing object, and its processing accuracy is generally ten microns;
(3) Laser micromachining technology, aiming at all kinds of thin films with thickness less than 100 μm as the main processing object, its processing accuracy is generally less than 10 μm or even sub μm.
In the mechanical industry, precision usually refers to the small surface roughness and the small range of various tolerances (including position, shape, size, etc.). The "precision" here refers to the small gap in the processed area, that is to say, the limit size that can be achieved by processing is small.
In the above three types of laser processing, the laser processing technology of large-scale parts has become increasingly mature, and the degree of industrialization has been very high; laser microprocessing technology such as laser fine-tuning, laser precision etching, laser direct writing technology has also been widely used in the industry.
Laser precision machining has the following remarkable features:
(1) Wide range: laser precision machining has a wide range of objects, including almost all metal and non-metal materials; suitable for sintering, drilling, marking, cutting, welding, surface modification, and chemical vapor deposition of materials.
Electrochemical machining can only process conductive materials, photochemical machining can only be used for corrosive materials, plasma machining is difficult to process some materials with a high melting point.
(2) Precise and meticulous: the laser beam can be focused to a very small size, so it is particularly suitable for precision machining. In general, laser precision machining is superior to other traditional machining methods because of its few influencing factors and high machining accuracy.
(3) High speed and high speed: from the perspective of machining cycle, EDM tool electrode requires high precision, large loss, and long machining cycle; electrochemical machining of cavity and surface cathode mold design workload is large and manufacturing cycle is long; photochemical machining process is complex; laser precision machining operation is simple and the slit width is easy to control, which can be output immediately according to the computer drawing High-speed engraving, cutting and processing are fast, and the processing cycle is shorter than other methods.
(4) Safe and reliable: laser precision machining belongs to non-contact machining, which will not cause mechanical extrusion or mechanical stress on materials; compared with EDM and plasma arc machining, its heat affected zone and deformation are very small, so it can process very small parts.
(3) Low cost: not limited by the number of processing, for small batch processing services, laser processing is cheaper. For the processing of large products, the mold manufacturing cost of large products is very high, laser processing does not need any mold manufacturing, and laser processing can completely avoid the collapse of material during punching and shearing, which can greatly reduce the production cost of enterprises and improve the quality of products.
(6) The cutting seam is small: the cutting seam of laser cutting is generally 0.1-0.2mm.
(7) Smooth cutting surface: the laser cutting surface is free of burrs.
(8) Small thermal deformation: the laser cutting seam of laser processing is thin, fast and energy concentrated, so the heat transferred to the material to be cut is small, resulting in very small deformation of the material.
(9) Material saving: laser processing with computer programming, can be different shapes of products for material nesting, maximize the utilization of materials, greatly reduce the cost of enterprise materials.
(10) It is very suitable for the development of new products: once the product drawings are formed, laser processing can be carried out immediately, and you can get the new products in the shortest time.
In general, laser precision machining technology has many advantages over traditional machining methods, and its application prospect is very broad.
Generally, the lasers used for precision machining are: CO2 laser, YAG laser, copper vapor laser, excimer laser, and CO laser.
Among them, high-power CO2 laser and high-power YAG laser are widely used in large-scale laser processing technology; copper vapor laser and excimer laser are widely used in laser microprocessing technology; medium and low-power YAG laser is generally used in precision processing.
(1) Laser precision drilling
With the development of technology, traditional drilling methods can not meet the needs in many occasions. For example, it is impossible to process small holes with a diameter of tens of microns on hard tungsten carbide alloy, and deep holes with a diameter of hundreds of microns on hard and brittle red and sapphire by conventional machining methods.
The instantaneous power density of the laser beam is as high as 108 w / cm2. The material can be heated to the melting point or boiling point in a short time, and the above materials can be perforated. Compared with electron beam, electrolysis, electric spark, and mechanical drilling, laser drilling has the advantages of good quality, high repetition accuracy, high universality, high efficiency, low cost, and remarkable comprehensive technical and economic benefits. Foreign countries have reached a very high level in laser precision drilling.
A Swiss company uses a solid-state laser to drill holes in the turbine blades of aircraft. It can process micropores with diameters ranging from 20 μm to 80 μ m, and the ratio of diameter to depth can reach 1:80. The laser beam can also be used to process various kinds of micro shaped holes on brittle materials such as ceramics, such as blind holes, square holes, etc., which can not be achieved by ordinary machining.
(2) Laser precision cutting
Compared with the traditional cutting method, laser precision cutting has many advantages. For example, it can cut a narrow incision, there is almost no cutting residue, the heat affected area is small, the cutting noise is small, and it can save 15% - 30% of the material.
Because the laser can hardly produce mechanical impulse and pressure on the material being cut, it is suitable for cutting glass, ceramics, semiconductors, and other hard and brittle materials. In addition, the laser spot is small and the slit is narrow, so it is especially suitable for all kinds of precision cutting of small parts. A Swiss company uses a solid-state laser for precision cutting, and its dimensional accuracy has reached a very high level.
A typical application of laser precision cutting is to cut SMT stencil in printed circuit boards. The traditional processing method of SMT template is chemical etching. Its fatal disadvantage is that the limit size of the processing should not be less than the plate thickness, and the chemical etching process is complex, the processing cycle is long, and the corrosive medium pollutes the environment.
Using laser processing, not only can overcome these shortcomings, but also can reprocess the finished template, especially the processing accuracy and gap density are obviously better than the former, and the production cost is also slightly lower than the former from the early far higher than the chemical etching. However, due to the high technical content and high price of the whole set of equipment for laser processing, only a few companies in the United States, Japan, Germany, and other countries can produce the whole machine.
(3) Laser precision welding
The heat-affected zone of laser welding is very narrow and the weld is small, especially it can weld high melting point materials and dissimilar metals, and it does not need to add materials. In foreign countries, solid-state YAG laser has been used for seam welding and spot welding at a high level. In addition, the laser welding of the outgoing line of the printed circuit does not require the use of flux and can reduce the thermal shock and have no impact on the circuit core, thus ensuring the quality of the integrated circuit core.
After more than 20 years of efforts, in laser precision machining technology and complete set of equipment, although China has been applied in laser spot welding, seam welding, airtight welding and marking of ceramic laser scribing and micro and small metal parts, but in laser precision machining technology, microelectronic circuit template precision cutting and etching technology, ceramic with high technology content and wide application market The laser precision machining of through-hole, blind hole, abnormal hole and groove of various sizes on porcelain and the printed circuit board is still in the stage of research and development, and there is no corresponding industrial prototype.
In recent years, a few large foreign companies have seen the huge potential market in the laser precision processing industry in China and have started to set up branches in China. However, the high cost of processing increases the cost of products, and many enterprises are still deterred.
Laser with high quality, high efficiency, stability, reliability, and low cost is the premise of the popularization and application of precision machining. One of the development trends of laser precision machining is the miniaturization of the machining system. In recent years, the development of the diode-pumped laser is very rapid. It has a series of advantages, such as high conversion efficiency, good stability, good beam quality, small size, and so on. It is likely to become the main laser for the next generation of laser precision machining.
The integration of the machining system is another important trend of laser precision machining. It is an inevitable trend for the development of laser precision machining to systematize and perfect the laser precision machining process of various materials, develop special control software with friendly user interface and suitable for laser precision machining, and supplement it with corresponding process database, combine the control, process and laser to realize the integration of optical, mechanical, electrical and material processing.
Although there is a big gap between China and foreign countries in laser processing technology and equipment, if we continuously improve the laser beam quality and processing accuracy on the original basis, combined with the processing technology research of materials, occupy the laser precision processing market as much as possible, and gradually penetrate into the laser microprocessing field, we can promote the rapid development of laser processing technology Finally, laser precision machining will form a large-scale industry.