Application of the hottest laser processing in mol

2022-08-18
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The application of laser processing in the mold industry

with the development of science, we usually judge from the following three points: the development of technology and the diversification of social needs, the competition of products is becoming more and more intense, and the renewal cycle is becoming shorter and shorter. Therefore, it is required not only to design new products as soon as possible according to the requirements of the market, but also to manufacture prototypes in the shortest possible time, so as to conduct performance tests and modifications, and finally form finalized products. In the traditional manufacturing system, a lot of mold design, manufacturing and debugging work is required, which has high cost and long cycle, and can not adapt to the changing market changes. In order to improve the speed of R & D and production, make high-quality and low-cost molds and products quickly and accurately, and make an agile response to market changes, people have done a lot of research and exploration work. With the continuous decline of the price of industrial lasers and the increasing maturity of industrial laser processing technology, great changes have been brought to the mold manufacturing and product production process. This paper first introduces the industrial processing laser, and then introduces and analyzes several aspects, such as mold laser manufacturing, mold surface laser strengthening and replacement, mold laser repair, mold laser cleaning and so on

industrial processing lasers

at present, industrial lasers used for laser processing mainly fall into two categories: solid-state lasers and gas lasers. Among them, the solid-state laser is represented by nd:yag laser; The gas laser is represented by CO2 laser. With the development of laser technology, people have begun to use high-power fiber lasers and high-power semiconductor lasers in some processing applications

1) nd:yag laser

the laser working material of nd:yag laser is solid nd:yag rod, and its laser wavelength is 1.06 μ m。 Due to the low laser conversion efficiency and the limitation of YAG rod volume and thermal conductivity, the average laser output power is not high. However, because nd:yag laser can compress the pulse width of laser output through Q-switch, it can obtain high peak power (108W) when working in pulse mode, which is suitable for laser processing applications requiring peak power; Another advantage is that it can be transmitted through optical fiber, which avoids the design and manufacture of complex transmission optical path, and is very useful in three-dimensional processing. In addition, the laser wavelength can also be converted to 355nm (UV) by frequency tripling technology, which is applied in laser stereo forming technology

2) CO2 laser

the laser working substance of CO2 laser is CO2 mixed gas, and its main applied laser wavelength is 10.6 μ m。 Because this kind of laser has high laser conversion efficiency, and the heat generated by the laser can be quickly transferred outside the laser gain area through convection or diffusion, its average laser output power can reach a high level (above 10000 watts), meeting the requirements of high-power laser processing

high power CO2 lasers used for laser processing at home and abroad are mainly cross flow and axial flow lasers. ① Crossflow laser: the beam quality of crossflow laser is not very good. It is multi-mode output and is mainly used for heat treatment and welding. At present, China has been able to produce various high-power cross flow CO2 laser series, which can meet the domestic needs of laser heat treatment and welding. ② Axial flow laser: the beam quality of axial flow laser is good, which is the output of basic mode or quasi basic mode. It is mainly used for laser cutting and welding. The market of laser cutting equipment in China is mainly occupied by foreign axial flow lasers. Although domestic laser manufacturers have done a lot of work on foreign axial-flow lasers, because the main accessories still need to be imported, the product price is difficult to decline significantly, and the penetration rate is low

Wuhan Bolai Technology Development Co., Ltd. has developed a swirling CO2 laser, as shown in Figure 1. With a new rotating gas flow mode, the swirling CO2 laser has the advantages of good beam quality, low cost and small volume of axial-flow CO2 laser and optical Jinan testing machine. The popularization 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

Figure 1 Wuhan Bolai Technology Development Co., Ltd.

500W swirling CO2 laser

mold laser manufacturing

1) laser indirect molding process

① stereo lithography apparatus (SLA) process uses UV laser beam to scan light curing adhesive layer by layer to form three-dimensional solid workpiece. In 1986, 3D systems of the United States launched a commercialized prototype sla-1. The maximum machining accuracy of SLA process can reach 0.05mm. ② The laminated object manufacturing (LOM) process uses thin sheet materials, such as paper and plastic film, and was successfully developed by American helisys company in 1986. Through repeated CO2 laser cutting and material pasting, the solid workpiece manufactured in layers is obtained. LOM Process is suitable for manufacturing large workpieces, with an accuracy of 0.1mm. ③ Selective laser sintering (SLS) process is formed by using powdered materials. It was successfully developed by the University of Texas at Austin in in 1989. Three dimensional workpieces are formed by selectively scanning the sintered material powder layer by layer with a high-intensity CO2 laser. The greatest advantage of SLS process is that it has a wide range of materials

the above three laser rapid prototyping technologies have been widely used at home and abroad due to their long development time and relatively mature technology. However, the three-dimensional workpiece formed by the above method cannot be directly used as a mold, and subsequent processing is required, so it is called laser indirect molding process. The main processing methods are: ① the rapid prototyping workpiece is used as a die after processing. The paper mold made by LOM directly replaces the sand mold casting wood mold after surface treatment; Or the paper mold made of LOM can be directly used as low melting point alloy mold and injection mold after surface treatment; Or the forming mold of wax mold in lost wax casting. The workpiece made by SLS is used as a metal mold after copper infiltration. ② The rapid prototyping part is used as the master mold to cast silicone rubber, epoxy resin, polyurethane and other materials to make the soft mold. ③ Use rapid prototyping parts to turn hard dies. One is to directly make paper-based mold with LOM, and then grind it into metal mold after surface metal arc spraying and polishing; The other is metal face hard backing mold. The above hard molds can be used for sand casting, pressure molding of EPC, injection mold and simple non steel drawing mold

the above laser indirect molding process can not only avoid complex mechanical cutting, but also ensure the accuracy of the mold, but also greatly shorten the molding time and save the molding cost. For the precision mold with complex shape, its advantages are particularly prominent. However, at present, there is still the disadvantage of relatively short die life, so the above laser indirect forming die is more suitable for small batch production

2) laser direct molding process

selective laser melting (SLM) technology is developed on the basis of selective laser sintering (SLS) technology. The characteristics of SLM are: (1) processing metal with high power density and small spot laser beam, so that the metal parts have a dimensional accuracy of 0.1mm; (2) The parts made of molten metal have metallurgical bonding entities, and the relative density can almost reach 100%, which greatly improves the performance of metal parts; (3) Because the laser spot diameter is very small, it can melt high melting point metals with low power, making it possible to manufacture parts with single component metal powder. Figure 2 shows all metal parts manufactured by German EOS GmbH using selective laser melting (SLM) process

Figure 2 all metal parts manufactured by German EOS GmbH with selective laser melting

(SLM) process

laser multilayer (or three-dimensional/three-dimensional) cladding direct rapid prototyping technology is a high-tech manufacturing technology developed on the basis of rapid prototyping technology combined with synchronous feeding laser cladding technology. Its essence is three-dimensional laser cladding under computer control. Due to the rapid solidification characteristics of laser cladding, the metal parts produced have uniform and fine dendrite structure and excellent quality, and their density and properties are equivalent to those of conventional metal parts. Laser multilayer cladding has developed a variety of methods, among which the most representative is the rapid prototyping technology of metal parts called laser engineered net shaping (lens) developed by Sandia National Laboratories in the United States. Stainless steel, maraging steel, nickel base superalloy, tool steel, titanium alloy, magnetic materials and nickel aluminum intermetallic compound workpieces have been successfully manufactured by this method, and the density of parts reaches nearly 100%. Figure 3 shows the metal mold manufactured by Sandia National Laboratory with lens technology

Figure 3 American Sandia National Laboratories' all metal molds made by laser

engineering net forming process (lens)

selective laser melting (SLM) technology and laser engineering net forming (lens) technology have been widely valued by the industrial and academic circles because of their good compactness of formed parts, high metallurgical combination and high precision, and long service life of the molds. A variety of equipment prototypes have been launched abroad, Some even began to commercialize; However, the current research and application in China is still in its infancy

in addition, there is a layered manufacturing technology (LOM) of metal parts based on laser fine cutting, which has the characteristics of rapid and low-cost manufacturing of large-scale and complex shape molds. As early as the 1980s, Nakagawa Weixiong research laboratory in Japan applied the metal sheet LOM technology to realize the layered rapid manufacturing of metal molds. Through development, the metal sheet LOM technology has been gradually applied to the manufacture of large interior and exterior trim molds such as automobiles and injection molds with complex flow channels

laser modification of mold surface

mold surface treatment has always been an important issue in the field of machining. With the development of new technologies and processes, many traditional treatment methods are not applicable. For the mold with complex shape, the most ideal surface treatment method is to use laser. It has almost no deformation. The surface hardness is higher than that of the conventional treatment method, and it is more wear-resistant and has a longer service life

1) laser transformation hardening

laser transformation hardening is also called laser quenching. Because the cooling rate of laser quenching is much higher than that of conventional quenching, very fine martensite can be obtained. Laser transformation hardening has the advantages of higher hardness than conventional quenching, less deformation, thin surface layer and local quenching, and does not affect the mechanical properties of the substrate

2) laser shock strengthening

laser shock strengthening is a technology that changes the physical and mechanical properties of the surface of materials by strong shock waves generated by the interaction between high-power density, short pulse laser beam and materials. In the process of laser shock, because the peak stress of shock wave induced by laser is greater than the dynamic yield stress of the material, the material produces dense, uniform and stable dislocation structure, makes the metal surface plastic deformation, and forms deep residual compressive stress, so as to improve the strength, wear resistance, corrosion resistance and fatigue life of metal parts. Its main advantages are: high impact pressure, and the strengthening depth is 4 ~ 8 times that of traditional shot peening; It can process parts that cannot be processed by traditional technology, such as small grooves, small holes and contour lines; After laser shock strengthening, the metal surface will not produce distortion, mechanical damage, thermal stress damage, and phase transformation

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