Knowledge sharing by Guangdong Shunde Teamwork Model Technology Co., Ltd, whom with over 20 years rapid prototyping experience.
Email: ken@gdtwmx.com
Website: www.gdtwmx.com
Laser Rapid Prototyping (LRP) is a new manufacturing technology that integrates advanced technologies such as CAD, CAM, CNC, laser, precision servo drives, and new materials. Compared with the traditional manufacturing methods, the prototype has high copying and interchangeability; the manufacturing process has nothing to do with the geometry of the prototype; the processing cycle is short, the cost is low, the general manufacturing cost is reduced by 50%, and the processing cycle is shortened by more than 70%; Technology integration to achieve design and manufacturing integration.
Recent developments in LPR include: stereolithography (SLA); selective laser sintering (SLS); laser cladding (LCF); laser near-sharpening (LENS); laser thin-film laminating (LOM) technology Laser induced heat stress forming (LF) technology and three-dimensional printing technology.
Stereolithography (SLA) technology
SLA technology is also called photo-curing rapid prototyping technology. The principle is that the computer-controlled laser beam scans the surface of the photosensitive resin as a raw material point by point. The thin layer (a few tenths of a millimeter) of the resin in the scanned area is cured by photopolymerization. Form a thin layer of the part. The workbench moves one layer thick distance downwards, so that the cured resin surface is coated with a new layer of liquid resin, and the next layer is scanned. This is repeated until the entire prototype is manufactured. Since the photopolymerization reaction is based on the action of light rather than on the effect of heat, a lower power laser source is required during operation. In addition, because there is no thermal diffusion, coupled with the chain reaction can be well controlled, it can ensure that the polymerization reaction does not occur outside the laser spot, so the processing accuracy is high, the surface quality is good, the utilization rate of the raw materials is close to 100%, and the shape can be manufactured. Complex and delicate parts with high efficiency. For larger parts, they can be fabricated by first forming a block and then bonding.
The United States, Japan, Germany, and Belgium have invested most of their manpower and material resources in researching this technology, and new products have been introduced. Xi'an Jiaotong University in China also successfully developed a three-dimensional light shaping machine LPs600A. At present, more than 10 factories around the world produce this product.
●Application in automobile body manufacturing
SLA technology can produce the required proportion of precision casting molds, thereby casting a certain proportion of the body metal model, the use of this metal model for wind tunnels and collisions and other tests to complete the final evaluation of the body to determine whether the design is reasonable. Chrysler Corporation of the United States has used the SLA technology to create a body model, put it in a high-speed wind tunnel for aerodynamic test analysis, and achieved satisfactory results, greatly saving the test costs.
● for automotive engine intake pipe test
The shape of the intake manifold cavity is composed of a very complex free-form surface, which has a very important effect on improving the intake efficiency and combustion process. During the design process, airway tests are required for different air intake pipe schemes. The traditional method is to manually process the tracheal wood mold or plaster mold described by dozens of sections, and then use the sand mold to cast the air intake pipe. The understanding of drawings by wood molders and their own level of technology often lead to deviations of parts from design intent. Sometimes the effect of such errors is significant. Although the use of numerical control processing can better reflect the design intent, but its preparation time is long, especially when the geometry is complex. British Rover Company used the rapid prototyping technology to produce the outer and inner cavity modes of the intake pipe, and achieved satisfactory results.
Selective Laser Sintering (SLS) Technology
The SLS technology is similar to the SLA technology except that the liquid photopolymer is replaced with a powdered raw material and applied to the powdered material with a certain scanning speed and energy. The technology has the advantages of wide selection of raw materials, easy removal of excess materials, and wide application range, and is applicable to the manufacture of original and functional parts. During the forming process, laser working parameters, powder properties, and sintering atmosphere are important parameters that affect the quality of the sintering process.
●Application in automobile mould manufacturing
The SLS technology studied by Texas State University has been commercialized by the American DTM company. At present, the company has developed the third generation of SLS2000 series products. The system can sinter wax, polycarbonate, nylon, metal and other materials. The steel copper alloy injection mold manufactured by this system can inject 50,000 pieces of workpieces. In recent years, mold manufacturing technology based on RPM technology has been developed from the original prototype manufacturing to rapid tool and mold manufacturing, and has become the focus of applied research and development at home and abroad. RPM-based mold manufacturing methods can be divided into direct frame method and indirect mold method.
The direct molding method directly uses the RPM technique to make the mold. The SLS method can be used to directly fabricate the metal mold in various methods of the RPM technology. The steel copper alloy injection mold manufactured by this method can have a life of more than 50,000 pieces. However, this method has a large shrinkage of the material in the sintering process, and the accuracy is difficult to control.
Indirect molding methods can be divided into:
(1) Production of soft simple molds
Using silicon rubber, metal powder epoxy powder and low-melting alloy, etc., to accurately reproduce the original shape into a mold, or surface treatment of the original shape, metal plating or physical vapor deposition method to coat a layer of alloy with a lower melting point to make a mold . The life span of these simple molds is 50-5000 pieces. Due to its low manufacturing cost and short cycle time, these simple molds are particularly suitable for small batch production in the trial production stage.
(2) Production of steel molds
Combining RPM technology with precision casting technology enables rapid manufacturing of metal molds. EDM electrodes with high complex precision can be directly manufactured for the machining of mold cavities such as injection molds, forging dies and die castings. A medium-sized, more complex electrode can generally be completed within 4 to 8 hours, and the accuracy of the complex shape fully meets the engineering requirements. Ford Motor Company used this technology to manufacture automotive molds and achieved satisfactory results. Shanghai Jiaotong University has also used RP and precision casting methods to produce more than 80 sets of imported and imported molds for the automotive and automotive tire industries. Compared with the traditional machining method, the manufacturing cost and cycle of rapid die manufacturing are greatly reduced. China needs to import more than 800 million U.S. dollars annually for molds, mainly complex molds and precision molds. Therefore, the application of SLS technology in the automotive mold manufacturing industry in the future is very promising.
●Application in automotive lighting manufacturing
The shape of most automotive lamps is irregular, the surface is complex, and mold making is difficult. Through rapid prototyping technology, accurate product samples can be quickly obtained, providing a good reference for mold design CAD and CAM. At the same time, it is also possible to manufacture lamp dies quickly and accurately by means of investment casting using rapid prototyping technology.
Laser Cladding Forming (LCF) Technology
The working principle of LCF technology is basically the same as that of other rapid prototyping technologies. It is also through the numerical control of the work table that the laser beam scans and claddings the powder and finally forms the part with the required shape. The results of the study show that the following factors are relevant: the part slicing method, laser cladding thickness, laser output power, spot size, light intensity distribution, scanning speed, scanning interval, scanning method, powder feeding device, powder feeding amount, and powder particle size. The precision and strength of the formed part have an effect.
The difference with other rapid prototyping technologies is that laser cladding can be used to make very dense metal parts. The strength of the laser cladding can reach or even surpass the parts produced by conventional casting or forging methods, and thus has a good application prospect.
Laser Near Lens (LENS) Technology
LENS technology combines SLS technology and LCF technology and maintains the advantages of both technologies. There are three types of metal powders used:
(1) single metal;
(2) metal plus low melting point metal binder;
(3) Metal plus organic binder. Due to the powder application method, the laser-sintered metal is low in density, porous, and low in strength regardless of the type of powder used. To increase the strength of sintered parts, post-treatments such as impregnating resin, low-melting-point metals, or hot isostatic pressing must be performed. However, these post-processing will change the accuracy of metal parts.
Laser Thin Film Laminate Manufacturing (LOM) Technology
LOM technology is a new type of rapid prototyping technology commonly used to make molds. The principle is to use a high-power laser beam to cut the metal sheet first, then stack the multi-layer sheet, and gradually change its shape, and finally obtain the desired original stereoscopic shape.
The production of the die by LOM technology costs about 1/2 less than the traditional method, and the production cycle is greatly shortened. For the production of composite molds, thin molds, progressive molds, etc., the economic benefits are also very significant. This technology has been widely used abroad.
Laser induced heat stress forming (LF) technology
The principle of LF technology is based on the characteristics of metal thermal expansion and contraction, that is non-uniform heating of the material, resulting in a predetermined plastic deformation. The technology has the following features:
(1) No mold forming: The production cycle is short and flexible, which is especially suitable for the production of single-piece small batches or large-shaped workpieces;
(2) No external force forming: The source of material deformation lies in its internal thermal stress;
(3) non-contact forming: high precision molding, no wear of the tool can be used for the manufacture of precision parts;
(4) Thermal accumulation molding: It is possible to form a hard-deformable material or a high-hardening index metal at room temperature, and a self-hardening effect can be produced, so that the structure and performance of the material in the deformed zone can be improved.
August 06, 2020
