Papers by Keyword: Selective Laser Sintering (SLS)

Abstract: The 3D transient finite element model in selective laser sintering is established based on ANSYS. The load of moving heat source at different time and locations are achieved by APDL and “element birth/death” technique, and the influence of convection, radiation, latent heat of phase change and thermal physical properties on temperature are taken into account. The temperature field distribution on time in forming process and temperature gradient distributions of pool cross-section are selectively studied, to provide theoretical basis for reasonable process parameters. The SLS experiment on PA6/Cu composite powders is carried out to verify the accuracy of simulation results.

Abstract: Based on CT data of the lesion of an orthopedic patient with knee, Mimics13.1, Magics9.5 can be used for the medical image processing. The CT image data were filtered, interpolated, sharpen, the interest region was extracted by the application of threshold segmentation method and was grown. The three dimension model of patient’s skeleton is reconstructed. Based on selective laser sintering, the digit model of patient’s skeleton reconstructed can be accurately transformed into the object model of the individual matching skeleton. The results indicated that the contour of reconstructed knee-joint bone object model were very coincident, and symmetric with knee-joint bone defect.

Abstract: Selective laser sintering technology is used for manufacturing parts from 316 stainless steel powders. Experiments were carried out on a Nd:YAG laser machine (LMY400) with 400W. Powder is layered by a roller over the surface of a 100mm diameter build cylinder. Effects of processing parameter on the scan line width, the scan line height, the single layer structure and the multilayer structure are investigated. The results show laser power, scan speed and layer thickness have a great effect on the scan line width and line height. Furthermore, the stable and continuous vectors are formed with the increasing of the number of layers.

Abstract: This paper presents an Object-Oriented class library for scanning path generation in SLS/SLM (Selective Laser Sintering/Selective Laser Melting) process. The classes in the library meet the minimal requirement for the scanning path generation. Specially, in order to take advantage of the Multiprocessor technology and save the generation time, parallel computing is considered in the class library. At last, an application was developed using the class library and an experiment is provided to verify the feasibility of the parallel computing algorithm in the library.

Abstract: Warpage is a crucial factor to accuracy of sintering part in selective laser sintering (SLS) process. In this paper, The influence of process parameters on warpage when sintering polystyrene(PS) materials in SLS are investigated. The laser power, scanning speed, hatch spacing, layer thickness as well as temperature of powder are considered as the main process parameters. The results showed that warpage increases with the increase of hatch space. Contary to it, warpage decreases with the increase of laser power. Warpage decreases with the increase of layer thickness between 0.16~0.18mm and changes little with increase of the thickness. Warpage increases along with the increase of scanning speed but decreases when the speed is over about 2000mm/s. When the temperature changes between 82°C-86°C, warpage decreases little with the increase of temperature. But further increase of temperature leads to warpage decreasing sharply when the temperature changes between 86°C-90°C.

Abstract: The dimensional accuracy and mechanics properties of parts made by Selective Laser Sintering depend greatly on the sintering process parameters. The influence of process parameters on warping weight of parts sintered by blends of polyamide (PA12) and high density polyethylene (HDPE) was studied. The relationship between the process parameters and the warping height was presented. The surface morphology of the part and uniformity of powder mixed were analyzed by SEM. The optimum parameters of minimum warping height were obtained: preheat temperature 110°C, scan speed 300mm/s, laser power 21W, thickness of single layer 0.2mm.

Abstract: Silica particles coated with PA12 by emulsion polymerization were used as fillers to reinforce PA12 based composites prepared by selective laser sintering (SLS). The influences of the treated and untreated particles on the sintering behavior and mechanical properties of the laser sintered specimens were investigated. It was found that there were many uneven holes in the untreated composites. However, for the treated composites, due to the silica particle surfaces treated by emulsion polymerization, the absorbance of laser was improved and the particles dispersed well in the polymer matrix; a full dense structure was obtained and the properties were enhanced, such as the tend strength increased 30%, the maximum value was 34MPa; the tensile strength increased up to 125%, the maximum value was 44.2 MPa, comparing to the unfilled PA12. Drawing from the results, it can be confirmed that a full dense structure can be obtained and the PA12 matrix was strengthened and toughened when the silica particles were coated with PA12 by emulsion polymerization.

Abstract: Nylon 12 composite powder with low melting point prepared by the method of solvent settling out as the basis material is modified with basis material added by all kinds of filling. With the ortho-design experiment method, the sintering process of nylon composite powder is optimized for sintering density and mechanical property of prototype parts. On this basis, the effects of the sintering process parameters on the properties of the parts are analyzed. The result shows this method can make nylon composite power with high powder density, precision and mechanical properties.

Abstract: A multi-component polymer-coated molybdenum powder was chosen for selective laser sintering (SLS). A novel preparing method of polymer-coated molybdenum powder was presented. The effect of the process parameters on the part’s characteristics is investigated. Based on our study for dynamic laser sintering process of polymer-coated molybdenum powder, its laser sintering mechanism was reported as follows: at the early stage of laser sintering, the viscous flow is the major mechanism; during the laser sintering, the melting/solidification is the major mechanism. Furthermore, a model corresponding to the mechanism was discussed schematically, which could be used to explain the material migrating mode during laser sintering process.

Abstract: The process of sintering material from the powder to the liquid with high temperature and then to the continuous solid are simulated, considering the effects of heat conduction, thermal radiation, thermal convection and thermal physical parameters on temperature. The results show that the temperature gradient is larger in the front of pool, and the end of which is smaller due to the fast-moving laser beam and uneven distribution of laser energy. With the increase of scanning time, the overall temperature of substrate and powder particles is gradually rising, the heat-affected zone is increasing and the asymmetric temperature distribution has become more obvious for the heat conduction. As the pool depth is larger than the powder thickness and the pool width is larger than the scanning spacing at the current process parameters, the bond strength of layers and scanning lines is enough.