| Selective laser sintering (SLS) is regarded to be a kind of promising technology for the fabrication of artificial bone. Hydroxyapatite (HAP) has been widely used as bone repair material due to its excellent biological performance. In this paper, aiming at the criticial technology for fabricating hydroxyapatite artificial bone by selective laser sintering, a control software with man-machine interface was developed, based on which the process rules and mechanism of adding small amount of poly (1-lactide acid)(PLLA) to improve the sintering property of HAP were studied. The main work and innovative results are as follows:1. A motion control software for a novel selective laser sintering system was developed to fabricate artificial bone, which adopted the library functions provided by a motion control card. The control for the output power of laser and interpolation motions of three-dimensional motion platform were realized. The problem that the transmission length of interpolation commands can not exceed certain value at a time due to constriction by the register capacity of the motion control card was resolved.2. The effect of different proportions of PLLA on the sintering behavior of HAP was investigated. The sintered HAP became more compact with a certain amount of PLLA (1wt%), together with the increase of hardness by20.7%.3. The microstructure evolution of sintered HAP was studied under different laser energy density. It was found that HAP grains grew up with the laser energy density increasing, and there were many strip-like cracks on the surface of sintering zone. The cracks gradually reduced until disappeared when the laser energy density increased to0.45J/mm2, together with a great improvement of density.4. The role of small amount of PLLA in enhancing the laser sintering properties of HAP powders was analysized. PLLA would undergo three processes of melting, carbonization and oxidation in the sintering process. The molten PLLA could enhance the particle rearrangement and densification of HAP by capillary force, which would lead to the improvement of sintering properties of HAP. The PLLA could also be oxidized gradually until completely excluded from the sintered HAP scaffolds under suitable processing parameters. |
