Physical modeling of the selective laser sintering process

Recent development of the innovative manufacturing techniques collectively called Solid Freeform Fabrication have impacted the conventional manufacturing industry. Selective Laser Sintering (SLS) is one of the most important techniques in Solid Freeform Fabrication. As more knowledge is required for improving the SLS technique, research on physical modeling of the SLS process is conducted in this dissertation.; This research starts with a thermodynamic study of an SLS system. An energy balance equation and the driving force of sintering are derived. An analogous system and a bond graph model are used to illustrate the behavior of an SLS system, and the dynamic response of a simplified SLS system is obtained.; An integrated model for the SLS process is developed, consisting of optical, thermal and sintering submodels. The optical submodel describes the interactions between the laser and powder bed, the thermal submodel describes the heat transfer behavior of a sintering powder bed, the sintering submodel describes the geometry deformation of the powder bed during the sintering process. Models of physical properties for each submodel as well as mathematical equations governing each submodel are derived. All of these submodels are quantitatively or qualitatively supported with experimental data.; A computer simulation program is developed based on the integrated model of SLS. Output of the computer simulation including the temperature and relative density of the powder bed are presented in a comprehensive format.; A general analysis of SLS behavior is conducted. The parametric analysis uses computer simulation results and experimental data to relate an important SLS property, sintering depth, with process control parameters including laser power, laser scanning speed and initial bed temperature. The morphology study gives a theoretical validation of a proposed geometric sintering structure.; This research not only provides an understanding of the SLS behavior and guidelines for modeling the SLS system, it also provides useful information in optimizing the SLS process and product quality. Since the model can be used to estimate SLS behavior, it can be used to guide and interpret SLS experiments.