Study Of Key Technologies Of Direct Prototyping Based On Semiconductor Laser Energy Source

Rapid Prototyping (RP) technology is a new subject that was developed in 1990s. It is an integration of CAD, laser technology, numerical control technology and the science of new materials. Direct metal laser sintering (DMLS) is an important branch of rapid prototyping and is a rapid prototyping technology of directly forming metal parts with high-power laser. CO2 laser,Nd:YAG laser or fiber laser is generally used in DMLS. Because semiconductor laser has some advantages, such as small volume, long life and high efficiency, semiconductor laser has more advantages than other lasers. The optimal advantage of semiconductor laser is small and easy to realize miniaturization device. If semiconductor laser is used in DMLS, DMLS equipment can becomes a kind of desktop 3D printing system that is suitable for battlefield hospital. This kind of desktop 3D printing system may timely repair key parts of combat weapon and has high precision. In recent years, the properties of semiconductor laser are rapidly improved. With increasing of power conversion efficiency and output power of high-power semiconductor laser, it is possible that semiconductor laser may be directly used in material processing field. This paper designs an energy source of near infrared semiconductor laser, discusses the interaction mechanism between near infrared laser and metal powder and studies key technologies of 316L stainless steel metal powder prototyping using near infrared semiconductor laser.This paper designs an energy source of near infrared semiconductor laser at first. This energy source adopts near infrared semiconductor laser of 1.06μm wavelength. Due to the semiconductor laser beam has high divergence, this paper studies the scheme of collimating and expanding beam in order to meet beam requirement of forming metal parts. Parameters of used optical devices are calculated.This paper discusses the interaction mechanism between near infrared laser and metal powder, analyzes the relation between absorption of metal powder and laser wavelength, discusses change of the metal powder thermal physical parameters in DMLS processing, and analyzes parameters of material and technology in laser sintering processing.In order to deep analyze DMLS process, this paper builds 3D finite element model of temperature field with ANSYS software. The temperature field of laser sintering 316L stainless powder is simulated and process parameters are calculated, such as sintering depth, scanning interval, and so on. In the simulation process, convection boundary condition and latent heat are considered. The change of material thermal physical parameters varying with temperature is considered. On the basis of simulation, sintering experiment has done in laboratory and the result of experiment is approximately consistent with simulation.In order to improve forming efficiency and accuracy, slicing algorithm based on STL file and direct slicing algorithm are studied and improved.According to the characteristics of near infrared semiconductor laser, variable focal length scanning method is given. Because the wavelength of near infrared semiconductor laser is smaller than the wavelength of CO2 laser, smaller focal spot may be gotten and this is beneficial to improve forming precision. In order to improve accuracy without reducing forming efficiency, smaller focal spot is used in scanning contour and bigger focal spot is used in filling interior. According to variable focal length scanning method, the forming power of 1.06μm near infrared semiconductor laser is compared with the forming power of CO2 laser.