Material Movement and Fusion Behavior of TrueForm and TrueForm/SiO2 during Selective Laser Sintering 146
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Different material systems, TrueForm and TrueForm/SiO2 composites, were sintered under similar conditions. A microscope equipped with a CCD camera was utilized to examine the material movement near the laser beam. Powder movement of the blends was found to start at different ranges ahead of the line of scan. For TrueForm, the polymer particles were found to undergo fusion ahead of the laser beam and form a band, 0.5-0.7mm wide, which then moved as a single block towards the sintered area. The dry mixed TrueForm/SiO2 composites (dry blends) exhibited a short-range material movement in the form of small agglomerates. Meanwhile, the TrueForm/SiO2 composite powder prepared by melt extrusion (melt blend) showed a range of material movement between those of TrueForm and the dry blends. The discrepancy is believed to arise from changes in heat transfer properties and fusion behavior after blending. The surface temperature of the powder bed was monitored during sintering. Generally, the dry blends exhibited a higher surface temperature. Apparently, both the particle size of SiO2 and the blending method had an effect on the temperature and material movement, and hence on the final morphology of the sintered components.