Browsing by Subject "Laser Sintering"

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Characterization of Selective Laser Sintering™ Materials to Determine Process Stability
(2002) Gornet, T.J.; Davis, K.R.; Starr, T.L.; Mulloy, K.M.
The Selective Laser Sintering (SLS) process has proved to be an excellent method for prototyping functional parts out of engineering thermoplastics such as polyamides. However, the material undergoes physical and chemical changes due to repeated heating cycles in the SLS equipment. This causes variations in powder characteristics and performance in the SLS process. With the increased utilization of SLS for direct manufacturing it is necessary to develop a characterization and testing system that can determine powder fitness to ensure process stability and part quality. Current powder recycling methodologies use an average virgin-to-used powder mixture. In a new approach, a testing mechanism to deliver a numerical, measurable material characterization will be discussed. Experimental results of repeated reuse of material and its resulting physical effects on mechanical properties, shrinkage, and chemical tests will be presented. A definitive testing and measurement process control will be shown to improve process stability and thus part quality and consistency.
Establishing the Performance Requirements for Stab Resistant Additive Manufactured Body Armour (AMBA)
(University of Texas at Austin, 2012-08-22) Johnson, A.; Bingham, G.A.; Majewski, C.E.
Body armour is worn to lessen the likelihood of sustaining a life threatening injury. Such protective solutions are used every day by law enforcement officers around the world, with strict guidelines governing their design and testing. These activities are monitored by government departments such as the Home Office Scientific Development Branch (HOSDB) within the United Kingdom (UK), and the National Institute of Justice (NIJ) within the United States. Despite providing protection against significant levels of impact energy, a number of historical issues continue to be present with modern fibre-based soft body armour – which once addressed may demonstrate an enhancement wearer operational performance. This paper therefore presents research highlighting such issues, and demonstrates how Additive Manufacturing (AM) technologies, particularly Laser Sintering (LS), could potentially be used to address such operational concerns whilst providing protection against a real-world threat. Results documented within this paper demonstrate that 5.6 mm thick planar samples, Laser Sintered from a 50/50 mix of virgin and recycled PA 2200 successfully achieved penetration resistance to the UK HOSDB KR1 impact energy of 24 joules. These results therefore influenced the design, manufacture, and testing of a series of AM textile samples featuring an imbricated layout, which also demonstrated successful knife penetration resistance to the HOSDB KR1 level – thus developing stab resistant Additive Manufactured Body Armour (AMBA).
Nitrogen Flow Effects on Part Bed Surface Temperature during Laser Sintering
(University of Texas at Austin, 2013-08-16) Yuan, Mengqi; Bourerll, David
The role of nitrogen flow rate was invested as it affects the surface temperature of a polymer laser sintering part bin. A SinterStation 2500® was used for this study. The effect of nitrogen chamber flow rates between 0.5 and 2.5 m3/hr was observed and compared to the results of a computational fluids dynamics model. Increasing convective flow generates a uniform reduction in the surface temperature, but it does not meaningfully reduce surface temperature gradients. The part bin piston was modified to allow down drafting of nitrogen through the part bin. Down drafting, while once considered to be effective in accelerating cooling at the end of builds, did not have a significant effect on the surface temperature profile.
Selective Heat Sintering Versus Laser Sintering: Comparison of Deposition Rate, Process Energy Consumption and Cost Performance
(University of Texas at Austin, 2015) Baumers, M.; Tuck, C.; Hague, R.
The Selective Heat Sintering (SHS) process has become available as a low cost alternative to Laser Sintering (LS) for the additive deposition of polymer objects. While both processes belong to the powder bed fusion variant of Additive Manufacturing (AM) technology, their operating principles vary significantly: SHS employs a thermal print head to selectively fuse material powder, whereas the LS approach utilizes a laser beam coupled with a galvanometer. Based on a series of build experiments, this research compares these technology variants along three dimensions of process efficiency: deposition rate (measured in cm³/h), specific process energy consumption (MJ/kg) and specific cost ($/cm³). To ensure that both platforms are assessed under the condition of efficient technology utilization, an automatic build volume packing algorithm is employed to configure a subset of build experiments. Beyond reporting absolute and relative process performance, this paper additionally investigates how sensitive the compared processes are to a variation in the degree of capacity utilization and discusses the application of different levels of indirect cost in models of low cost AM.
Selective Laser Sintering of SiC/Polyamide Matrix Composites
(2002) Gill, Toby; Hon, Bernard
This paper presents an experimental study into the production of particulate Silicon Carbide/Duraform Polyamide matrix composites via the selective laser sintering (SLS) process. FEPA standard SiC grits, F240 and F360, were each individually blended with the commercially available Duraform Polyamide, to produce blend compositions of 50 and 60 volume percent SiC for direct SLS processing. A full factorial experimental approach was applied to examine the effects and interactions of laser power, scan speed, scan spacing and layer thickness, with regards to the mechanical and physical properties of sintered parts. Analysis of parameter interactions and individual main effects as well as Pareto analysis for all parameter combinations are presented for the responses of part porosity and strength.
A Three Dimensional FEM-Simulation of the Selective Laser Sintering Process with Locally Refined Meshes and Non-Constant Thermal Conductivity
(2002) Boillat, E.; Kolossov, S.; Glardon, R.