Papers by Keyword: Laser Sintering

Abstract: Powder bed fusion (PBF) is an additive manufacturing technique, which allows to build complex functional mechanical parts layer-by-layer, starting from a computer-aided design (CAD) model. PBF is particularly attractive for biomedical applications, where a high degree of individualization is required. In this work, the microstructure of two biomedical alloys, namely Co-Cr-Mo and Ti-6Al-4V, were studied by X-ray diffraction and electron microscopy techniques. Hardness and tensile tests were performed on the sintered parts.

Abstract: Water-based suspensions from commercial Tetragonal stabilized zirconia (3Y-TZP) were produced and characterized with different contents of solids and two different dispersants. According to zeta potential measurements, 3Y-TZP particles showed basic surface characteristics and IEP of around 9 when in aqueous media. The critical volume fraction of solids was about 79.6 wt%, which hindered the processing of more concentrated slurries. Rheological measurements confirmed that well dispersed slurries could be obtained with solid content as high as 79.6 wt.%. The results showed that Triton X-114 was an effective dispersant for preparing well stabilized 3Y-TZP suspensions for the layer-wise slurry deposition process.

Abstract: The model of laser sintering with regard to explicit porosity evolution of powder layer has been suggested. Due to porosity reduction the shrinkage occurs, thermal - physical properties (the heat capacity, thermal conductivity coefficient) and reflection coefficient of laser irradiation change. It has been shown that additional mechanism of convective heat transfer connects with powder layer thickness evolution. It was detected that model obeys some prognostic properties and allows to reveal the area of technological parameters where homogeneous properties of sintered layer form.

Abstract: The aim of this paper is to present the manufacturing technologies for fixed prosthetic restorations frameworks as well as the materials suitable for these applications.For fixed prosthetic restorations frameworks the most used materials at present are Co-Cr alloys and zirconia.Co-Cr dental alloys have been used, mainly for removable partial dentures, for many years. Recently they began to be used more and more for fixed prosthodontics as well, because they do not develop the high allergenic response as Ni based alloys and are not as difficult to manipulate as titanium.Zirconia is used for frameworks manufactured by CAD/CAM milling and it has certain advantages when compared to Co-Cr dental alloys: esthetics, resistance, mechanical properties, biocompatibility, resistance to corrosion, weight but it’s much more expensive.The practitioner has certain options for fixed prosthodontics frameworks manufacturing and the final choice should be made according to the particularities of each case.

Abstract: In view of the physical process of the wood powder/PES composite powder material selective laser sintering forming ,this article establishes the plane moving Gaussian heat source as the input laser heat source model .Based on selective laser sintering wood powder/PES composite powder sintering theory and combined with thermal conductivity of composite powder, specific heat, density and other related theoretical analytical models .It establishes three dimensional finite element model of selective laser sintering process of wood powder/PES composite powder transient temperature field .The laser sintering simulation experiment of wood powder/PES composite powder under different laser power obtains temperature field distribution law of the wood powder/PES composite powder forming under different laser power distribution, and the influence of the forming parts forming quality of wood powder/PES composite powder materials caused by the temperature field. The simulation results also provide certain theoretical basis for the choice of laser power in the subsequent laser sintering experiment.

Abstract: . Based on orthogonal test, the forming accuracy and density of laser sintering eucalyptus/PES blend is studied in this paper. It mainly analysed the effect of the powder size and process parameters (such as laser power, layer thickness, preheating temperature, etc) on the forming precision and density of sintered eucalyptus/PES parts, also the correlation analysis of molding error caused by the powder’s physical properties and machine is performed. By measuring the parts’ dimensions, the results show that the laser power and powder size are two main factors influencing parts’ density, and variable density, layer thickness and preheating temperature jointly affect the dimensional accuracy. The optimized processing parameters are obtained. The powder size, laser power, scanning rate, layers thickness and preheating temperature are 300 mesh, 43W, 2000mm/s, 0.1mm, 60°C respectively.

Abstract: One of the challenges which Laser Sintering faces is the Rapid Manufacturing of plastic parts with good consistent quality. This is due to the fact that plastic powder properties deteriorate during the long periods of time through the LS building and cooling cycles. This paper presents an experimental study of the deterioration or ageing of PA12 powder properties in the LS process. The influences of different grades of recycled PA12 powders are investigated. The main aim of this research is to develop a methodology of controlling the input material properties that will ensure consistent and good quality of the fabricated parts. From the experiment it was found that PA12 powder with high melt flow rate, low melting temperature, low glass transition temperature and low degree of crystallization temperature could improve the sintering process to produce a good Laser Sintering (LS) parts with lower shrinkage rate.

Abstract: The paper presents the dimensional aspects of a generic spinal cage build up from PA2200 powder. The cage was manufactured by means of selective laser sintering (SLS) technology, on Formiga P100 machine. The geometric model of spinal cage was designed in SolidWorks by taking into account the requirements that have to be fulfilled by such an implant. The dimensional aspects refer to geometric dimensions along X, Y and Z axes measured on sample parts, when these were placed on a 4x4 matrix on the building plane. The measurements were conducted using a digital caliper having a precision of 0.01, and were presented together with the nominal dimension of the CAD model. In conclusion, some qualitative aspects regarding the setting of the scaling factors were underlined.

Abstract: In this work, a hydroxyapatite (HA) bioceramic and a silica binder were used as the raw materials for manufacturing bioceramic bone scaffold after sintering by a laser beam in a home-made 3D Printing (3DP) machine. Results indicate that the bending strength of the scaffold can be improved after heat-treatment. While simultaneously increasing surface roughness conducive to osteoprogenitor cell adhesion. The processing parameters of a 90 mm/s laser scanning speed, 12 W of laser energy and 10 kHz of scanning frequency were used to fabricate a porous scaffold model, which possesses suitable biocompatibility and mechanical properties, allowing adhesion and proliferation of bone cells. Therefore, this process has great potential for manufacturing bone scaffolds.

Abstract: Selective Laser Sintering (SLS) or Laser Sintering (LS) allows functional parts to be produced in a wide range of powdered materials using a dedicated machine, and is thus gaining popularity within the field of Rapid Prototyping (RP). One of the advantages of employing LS is that the loose powder of the building chamber can be recycled. The properties of polymer powder significantly influence the melt viscosity and sintering mechanism during Laser Sintering (LS) processes which results in a good surface finish. The objective of this research is to investigate the chemical composition of fresh polymer materials used in Laser Sintering. There are seven virgin SLS materials which are PA2200, GF3200, Alumide, PrimeCast, PrimePart, Duraflex and CastForm. Fourier Transform Infrared Spectroscopy (FTIR) was used to analyze the chemical composition of the materials by using infrared radiation and absorbed frequency. The spectra show that similar functional groups were found in the materials apart from PrimePart and Duraflex. Obtained data from this analysis could be used to investigate on how the fresh and recycled powder materials with different chemical properties would affect the part surface finish.