The biggest difference between a 3D printer and a traditional printer is the raw materials used. The 3D printer uses not the ink, but the actual raw materials. In 3D printing, the software performs a series of digital slicing through CAD (Computer Aided Design) technology and transmits this information to a 3D printer, which prints the layers in layers and stacks successive thin layers until an object is formed. According to the different molding principles, 3D printing technology can be roughly divided into the following four types. 1.1, SLA technology stereo curing technology (SLA, stereolithographyapparatus), SLA technology is the earliest development of 3D printing technology, the technology uses liquid photosensitive resin as raw material, mainly used in mold manufacturing, is still one of the mainstream technologies of 3D printing . The SLA technology process is as follows: firstly, the three-dimensional model is sliced to generate scan path data; the laser beam is irradiated onto the surface of the liquid photosensitive resin along the scan path, and the irradiated resin layer is photopolymerized to solidify to form a thin layer of the part; Then the lifting platform is lowered to a certain height, and another layer of liquid resin is covered on the surface of the solidified layer and subjected to the second laser scanning; thus, the layers are stacked to form a prototype of the three-dimensional part. Finally, the prototype is taken out of the resin, and the product is obtained by grinding, electroplating, painting, and the like. SLA technology has the advantages of high molding speed, high printing precision, good surface quality, large print model size (up to 1524mm), etc., but due to the shrinkage of the resin during curing, inevitably, stress or deformation will occur. Therefore, the development of photosensitive materials with small shrinkage, fast curing and high strength is the development trend of SLA technology. 1.2, FDM technology Fusion molding technology (FDM, fuseddepositionmodeling), this method was invented by Scott·Crump in the 1980s. The FDM technology uses filamentous materials such as paraffin, metal, plastic, and low-melting alloy wire as raw materials to heat the wire to a temperature slightly higher than the melting point. Usually, the temperature is controlled by 1 ° C higher than the melting point. The print head is moved in a plane according to the sectional information provided by the computer, and the molten material is coated on the workbench, and after cooling, a section of the part is formed; after that, the print head is moved up to a certain height to apply the next layer of the material. This way, three-dimensional parts can be formed by stacking layer by layer. FDM technology is mainly used for the molding of small and medium-sized workpieces, and has the advantages of low cost, low pollution and recyclable materials. The main disadvantages are less accurate accuracy, slower manufacturing speeds, and limited types of materials used. 1.3, SLS technology Selective laser sintering technology (SLS, selective laserersintering), SLS technology was originally proposed by Carl Cardard of the United States in his master's thesis in 1989. The SLS technology uses a laser to selectively stratify sintered solid powder and superimpose the sintered solidified layer to produce the desired part. The working principle of SLS technology is as follows: the powder cylinder piston rises during operation, the powder roller rolls a layer of powder evenly on the piston of the forming cylinder, and the computer controls the scanning path of the laser beam to selectively sinter the solid powder material to form a layer of the part. After the completion of one layer of sintering, the working piston is lowered by a layer thickness, the powder spreading system is re-laid with powder, and the laser beam is scanned again to sinter the new layer. This cycle is repeated until the three-dimensional part is formed. The most outstanding advantage of SLS technology is that it can be used in a wide range of materials. Currently available materials for SLS technology are paraffin, polymer, metal, ceramic powder and composite powders thereof. Metal powder SLS technology is a hot topic in recent years, which can directly sinter high-strength parts that are difficult to manufacture in traditional cutting processes. 1.4, LOM technology Layered entity manufacturing technology (LOM, laminated object manufacturing), this technology is a rapid prototyping technology successfully developed by Helisys in the United States in 1991. The materials commonly used in LOM technology are paper, metal foil, plastic film, ceramic film, etc. In addition to making molds and models, this method can also directly manufacture structural parts. The LOM technology is shaped as follows: The laser cutting system laser-cuts the hot-melt-coated paper into the inner and outer contours of the component according to the cross-sectional profile data extracted by the computer, and cuts the waste into a mesh. After cutting a layer, a new layer of paper is superimposed and bonded to the cut layer by a hot-adhesive device for the next cut, which is repeated and eventually forms a three-dimensional member. LOM technology is characterized by low cost, high efficiency, stability and reliability, and is suitable for large-scale production. The disadvantage is that the front and rear processing is complicated and the hollow member cannot be manufactured.