Study On The Part Precision And Compressive Strength Of Selected Laser Sintering

With the progress and development of science and technology, people’s living standard has been greatly improved, and the demand for material is raised to a higher level. Traditional manufacturing has not fully met the needs of the production and the people’s daily life, and the industrial products developed into varieties, small batch, high precision and complication. Appeared in the late 1980s, the selective laser sintering is a widely used technology in many fields. It integrates computer technology, numerical control technology, laser technology, materials technology and other technology and process. Compared with the traditional manufacturing technology, the selective laser sintering has a wide applicability, simple process, high degree of automation, and it can be make sintered parts directly, especially suitable for making investment casting mould and sand casting mould. At present, the selective laser sintering technology has been widely used in automobile machinery, medical, construction, aerospace, rapid manufacturing precision casting die, arts and crafts design, and made a profound impact on the people’s life and the mode of production. The selective laser sintering has great potential applications in many industries. However, as a relatively new manufacturing technology at present, there are many problems existed in selective laser sintering technology:the cost of the SLS equipment is higher, and it cannot be used for forming a variety of materials, the molding speed is low, the surface quality and the forming precision is not high, and the intensity cannot meet the application requirements, etc. The research and progress of the 3D printing technology are discussed synoptically to solve the above problems, and the principle and application. Existing problems of the selective laser sintering technology are introduced in this article. Use theHRPS- Ⅳ laser rapid prototyping system as the test platform, this article designed test, which can research the multiple parameters of selective laser sintering performance of the polystyrene and coated sand. The technological parameters are optimized. The main conclusions are as follows:(1) When the scanning speed is 2000 mm/s, using polystyrene powder forming the best laser power is 20%, and using the precoated sand molding the best laser power is 45%. When the laser power is too small, and scanning speed is too fast, the molding materials are unable to get enough energy, which leads to large surface roughness, low dimensional accuracy, compressive tensile strength is not high. The molding material sintering is too full easily when the laser power is too large and the speed is too slow, and the phenomenon of burn out appeared, and all of these go against the von berg systeme forming quality eventually.(2) The best scanning interval is 0.2 mm for polystyrene, and the best scanning interval is 0.1 mm for the precoated sand. When the scanning the spacing is too large, scanning area separated from each other, it cause no connection and no overlap between laser scan line and line piece, and the total laser energy less than the energy of powder sintering need in the neighboring areas, it cannot make the powder sintering in the adjacent area, and it lead to the sintering area not firm between two bond adjacent, and seriously affecting the strength of the von berg systeme. When the scanning spacing is too small, most of the scanning line is overlap. The adjacent region of the laser energy can make the region part repeat sintering, uneven distribution of laser energy, so the powder sintering molding efficiency is reduced, and can cause von berg systeme larger warp and contraction. It can cause material vaporization and deformation when the laser scanning power continues to shrink.(3) The selection of laser sintering thickness of single layer had a great influence on surface roughness of von berg systeme. The best single layer thickness is 0.2 mm for polystyrene,, and the single layer thickness of 0.3mm for the precoated sand. It is generally believed that the smaller the thickness and the higher precision, the less the surface roughness of the von berg systeme, but when the slice thickness is too thin, the warping and deformation between the layer is appears easily, and the time of the sintering von berg systeme is too long.(4) For data pretreatment to the effect of selective laser sintering molding precision, the cause of data processing phase error and the error influence on von berg systeme precision and other performance were analyzed, and the von berg systeme put angle has a direct influence on the forming time and surface quality. The staircase effect can be produced when the surface of the CAD model has a irregular shape, and it has a littlest staircase effect when the surface close to the vertical ladder and a biggest staircase effect when the surface close to the horizontal direction.