Selective laser sintering (SLS) is a rapid prototyping method in which three-dimensional objects are constructed by sintering thin layers of a variety of powdered materials via laser beam. In SLS, as in most other Rapid Prototyping methods, the produced parts exhibit varying degrees of intrinsic porosity due to the discrete nature of layer-by-layer production. Selective scanning and discrete bonding of individual particles or clusters of particles impart local porosity, which is mostly an undesired trait as the part integrity decreases with increased porosity. However, there are a number of emerging or potential applications as in tissue engineering and composite/functionally graded materials, in which part porosity and its control during production are needed.
In this study, the manufacturing capabilities of selective laser sintering are investigated towards producing predesigned porous structures using a polymeric powder. The porous structures are characterized in two main categories: regular porous structures, which involve geometries such as predesigned holes and lattice structures that have orderly porous architecture, and irregular porous structures, which exhibit random pore architecture that is intrinsic in all SLS parts. The limitations of producing regular porous structures are investigated, identified and quantified, based on hole size and dimensional accuracy. An experimental analysis based on design of experiments is employed to investigate the effects of processing parameters on the resulting macroscopic pore properties of irregular porous structures. A mathematical relation is developed to quantify and predict the relations between the SLS process parameters: Laser power, hatching distance, laser scan spacing, and the resulting apparent mass density (as a measure of porosity). The subsequent tests verify accuracy of the developed empirical model.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12606529/index.pdf |
| Date | 01 August 2005 |
| Creators | Ilkgun, Ozkan |
| Contributors | Erdal, Merve |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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