Selective Laser Sintering Parameters Research Articles

Effects of Laser Power and Hatch Orientation on Final Properties of PA12 Parts Produced by Selective Laser Sintering.

Poly(dodecano-12-lactam) (commercially known as polyamide “PA12”) is one of the most resourceful materials used in the selective laser sintering (SLS) process due to its chemical and physical properties. The present work examined the influence of two SLS parameters, namely, laser power and hatch orientation, on the tensile, structural, thermal, and morphological properties of the fabricated PA12 parts. The main objective was to evaluate the suitable laser power and hatching orientation with respect to obtaining better final properties. PA12 powders and SLS-printed parts were assessed through their particle size distributions, X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), a scanning electron microscope (SEM), and their tensile properties. The results showed that the significant impact of the laser power while hatching is almost unnoticeable when using a high laser power. A more significant condition of the mechanical properties is the uniformity of the powder bed temperature. Optimum factor levels were achieved at 95% laser power and parallel/perpendicular hatching. Parts produced with the optimized SLS parameters were then subjected to an annealing treatment to induce a relaxation of the residual stress and to enhance the crystallinity. The results showed that annealing the SLS parts at 170 °C for 6 h significantly improved the thermal, structural, and tensile properties of 3D-printed PA12 parts.

Study on selective laser sintering process and investment casting of rice husk/ Co-Polyamide (Co-PA hotmelt adhesive) composite

The current available wood-plastic materials used for selective laser sintering (SLS) investment casting are often poor in fluidity in molten state, which is not easy to flow out the shell mold. This led to a large amount of residual ash in mold after heating and lowered the quality of the sintered parts. In this article, the Co-Polyamide (Co-PA Hotmelt adhesive) and rice husk powders (RH) were proposed as the feedstock of the rice husk (RH)/CO-PA composite (RHPA) for SLS. CO-PA with good fluidity was used as the matrix and RH powder as the additive materials. This paper aims to optimize the SLS processing parameters and determine the optimal ratio of RHPA parts manufactured by SLS. Through this work, an orthogonal experimental method of five factors and four levels was used to determine the optimum SLS parameters for the RHPA SLS test. The scan spacing, scan speed, laser power, layer thickness, and preheating temperature are chosen as main SLS affecting factors of this study. The synthesis weighted scoring methods were used to conclude the optimal combination of SLS parameters of RHPA i.e., scan spacing = 0.15mm, scan speed = 2m/s, laser power =16W, layer thickness = 0.25 mm and the preheating temperature = 74°C. Moreover, the influence of RH content on the mechanical properties, dimensional accuracy, and the residual ash content of RHPA parts was determined. When the ratio of RH powder on RHPA is 10 wt %, the bending strength of the sintered parts will reach 2 MPa. Besides, the residual ash content of RHPA parts after heating step was lower (1.1881%) and the tolerance level is CT5. Thus, the dimensional accuracy in X, Y, and Z directions of 10 wt % RHPA SLS parts is 99.79%, 98.71%, and 97.9%, respectively; and the surface of casting was smooth and clear details.

Selective Laser Sintering Parameter Optimization of Prosopis Chilensis/Polyethersulfone Composite Fabricated by AFS-360 SLS.

The current available selective laser sintering (SLS) materials are often high in cost and limited in variety; the mechanical properties of wood-composite SLS parts are low quality, which restricts the development of SLS technology. This article aims to optimize the SLS processing parameters to enhance the mechanical properties of the Prosopis chilensis powder (PCP)/polyethersulfone (PES) composite (PCPC) part fabricated via SLS. The PCP and PES powder were proposed as the feedstock of the PCPC powder bed for SLS. First, the thermal decomposition and glass transition temperatures (Tg) of PCP and PES powder were estimated to reduce the produced PCPC parts from warping and deformation during SLS. An orthogonal experimental methodology with five factors and four levels was used to optimize the SLS parameters for the PCPC SLS test. The scanning speed, preheating temperature, and laser power are selected as the main affecting factors on this study. The influence of these factors on dimension accuracies, bending and tensile strengths, and surface roughness quality of the produced PCPC parts was studied. The PCPC particle distribution and microstructure were inspected via scanning electron microscopy. Furthermore, the synthesis weighted scoring methods were utilized to determine the optimal SLS processing parameters of the produced PCPC parts. The combined results of tests showed that the optimal SLS parameters were as follows: the scanning speed is 1.8 m/s, preheating temperature is 80°C, and the laser power is 12 W. Thus, the quality of PCPC SLS parts was significantly enhanced when the optimal parameters were utilized in the SLS process. This article provided the main reference values of SLS parameters of the PCPC. To further enhance the surface roughness quality and mechanical strengths, the postprocessing infiltration with wax was introduced; after wax infiltration, the surface roughness and mechanical strengths were significantly improved.

Selective laser sintered nano-HA/PDLLA composite microspheres for bone scaffolds applications

Purpose The main cause of aseptic inflammation after an in vivo implantation is that Poly(L-lactide) (PLLA) and Poly(D-lactide) have a slower degradation and absorption rate, while Poly(D, L-lactide) (PDLLA) has a much faster degradation rate than PLLA because of its amorphous structure. Also, the hydrolyzate of Hydroxyapatite (HA) is alkaline, which can neutralize local tissue peracid caused by hydrolysis of Polylactic acid. Design/methodology/approach In this study, the selective laser sintering (SLS) technique was chosen to prepare bone scaffolds using nano-HA/PDLLA composite microspheres, which were prepared by the solid-in-oil-in-water (S/O/W) method. First, the SLS parameters range of bulk was determined by the result of a single-layer experiment and the optimized parameters were then obtained by the orthogonal experiment. The tensile property, hydrophobicity, biocompatibility, biological toxicity and in vitro degradation of the samples with optimized SLS parameters were characterized. Findings As a result, the samples showed a lower tensile strength because of the many holes in their interior, which was conducive to better cell adhesion and nutrient transport. In addition, the samples retained their inherent properties after SLS and the hydrophobicity was improved after adding nano-HA because of the OH group. Furthermore, the samples showed good biocompatibility with the large number of cells adhering to the material through pseudopods and there was no significant difference between the pure PDLLA and 10% HA/PDLLA in terms of biological toxicity. Finally, the degradation rate of the composites could be tailored by the amount of nano-HA. Originality/value This study combined the S/O/W and SLS technique and provides a theoretical future basis for the preparation of drug-loaded microsphere scaffolds through SLS using HA/PDLLA composites.

Preparation of high-porosity Al2O3 ceramic foams via selective laser sintering of Al2O3 poly-hollow microspheres

In this paper, high-porosity Al2O3 ceramic foams called Al2O3 PHM ceramics were fabricated through selective laser sintering (SLS) via Al2O3 poly-hollow microspheres (Al2O3 PHMs). SLS parameters were optimized by an orthogonal experiment as to be laser power = 6 W, scanning speed = 1800 mm/s, and scanning space = 0.15 mm. The effect of sintering temperature on microstructure, shrinkage, porosity, phase composition, mechanical properties and pore size distribution of Al2O3 PHM ceramics were investigated. When sintering temperature increased, Al2O3 PHM ceramics contained only Al2O3 phase and were gradually densified. With the raise of sintering temperature, the porosity of Al2O3 PHM ceramics decreased gradually from 77.09% to 72.41%, but shrinkage in H direction and compressive strength of Al2O3 PHM ceramics increased from 6.63% and 0.18 MPa to 13.10% and 0.72 MPa, respectively. Sintering temperature had little effect on pore size distribution of Al2O3 PHM ceramics, which only declined from 24.2 to 21.4 μm with the increase of sintering temperature from 1600 to 1650 °C. This method can not only directly prepare ceramic foams with complex shapes, but also control properties of ceramic foams. It provides a simple preparation method for many kinds of ceramic foams with complex structure and high porosity by using PHMs with different composition.

Fabrication of Al2O3‐SiO2 ceramics through combined selective laser sintering and SiO2‐sol infiltration

AbstractIn this study, different posttreatment methods, including silica‐sol infiltration (SI), vacuum silica‐sol infiltration (vSI), debinding (DB), and pressure‐less sintering (PS), were combined with selective laser sintering (SLS) to fabricate Al2O3‐SiO2 ceramics. The macro‐morphology and microstructure of sample fabricated under different laser processing parameters and posttreatment process were investigated. Results show that the geometric dimension accuracy and surface quality of the final samples can be effectively improved with appropriate SLS parameters and posttreatment. The optimal SLS processing parameters are determined to be 0.15 mm, 10 W, 0.1 mm, and 1500 mm/s for the hatch spacing, laser power, layer thickness, and scanning speed, respectively. The SLS/DB/vIN/FS samples have the smallest linear shrinkage ratio (<1%), the least warpage degree (<3%), and the best surface quality (surface altitude difference <170 μm). Mullite, quartz, corundum, and cristobalite composed the phases of the sample, of which cristobalite came largely from the infiltrated silica‐sol. Since a higher amount of silica‐sol infiltrated into the sample under SLS/DB/vIN/FS process, more cristobalite phase formed in the pore of the sample during sintering, which avoided excessive microstructure shrinkage during sintering and ensured the high geometric accuracy and surface quality of the final sample.

Process chain development for additive manufacturing of cemented carbide

Cemented carbide is a difficult material to be processed by Additive Manufacturing (AM) necessitating the need for process chain development to overcome the limitations of AM. Selective Laser Sintering (SLS) is proven to be the best AM process for making a complex product, and has potential to help produce a defect-free cemented carbide product. Consequently, in the present work, SLS is selected for process chain development study. Optimized SLS parameters are obtained to process WC-17Co (cemented carbide), which are able to furnish products of appreciable dimensional accuracy containing various fine features. In order to further improve product properties and remove any deficiencies, heat treatment is selected as a post-processing, which is accomplished in a furnace by heating samples at various temperatures (400, 600, 800 and 1000 °C) for a fixed duration of 3 h and by letting them cool inside the furnace. Samples are subsequently characterized to determine their hardness, fracture toughness, microstructure, wear resistance, composition of various phases and types of compounds formed. It is found that a moderate heat treatment has beneficial effects as the treatment at 600 °C furnished better hardness and fracture toughness while at 400 °C gave the best wear resistance. It is concluded that the heat treatment can be included as a complementary processing technique for producing cemented carbides as it has helped achieve products having better mechanical and wear properties.

Effect of Powder Size and Shape on the SLS Processability and Mechanical Properties of a TPU Elastomer

This work investigates the influence of powder size/shape on selective laser sintering (SLS) of a thermoplastic polyurethane (TPU) elastomer. It examines a TPU powder which had been cryogenically milled in two different sizes; coarse powder (D50∼200μm) with rough surfaces in comparison with a fine powder (D50∼63μm) with extremely fine flow additives. It is found that the coarse powder coalesces at lower temperatures and excessively smokes during the SLS processing. In comparison, the fine powder with flow additives is better processable at significantly higher powder bed temperatures, allowing a lower optimum laser energy input which minimizes smoking and degradation of the polymer. In terms of mechanical properties, good coalescence of both powders lead to parts with acceptable shear-punch strengths compared to injection molded parts. However, porosity and degradation from the optimum SLS parameters of the coarse powder drastically reduce the tensile properties to about one-third of the parts made from the fine powders as well as those made by injection molding (IM).

RETRACTED ARTICLE: Development and application of copper–nickel zirconium diboride as EDM electrodes manufactured by selective laser sintering

The production of electrical discharge machining (EDM) electrodes by conventional machining processes can account for over 50 % of the total EDM process costs. The emerging additive manufacturing (AM) technologies provide the possibility of direct fabrication of EDM electrodes. Selective laser sintering (SLS) is an alternative AM technique because it has the possibility to reduce the tool-room lead time and total EDM costs. The main difficulty of manufacturing an EDM electrode using SLS is the selection of an appropriate material. This work investigated the direct production of EDM electrodes by means of the SLS using a newly developed non-conventional metal–matrix composite material composed of a metallic matrix (CuNi) and an advanced ceramic (ZrB2). The influence of important SLS parameters and material content on the densification behavior and porosity of the electrodes was investigated. EDM experiments were conducted to observe the electrodes behavior and performance. It was found that the ZrB2-CuNi electrodes could be successfully manufactured by SLS. Interlayer bonding and porosity are directly influenced by the layer thickness. Smaller layer thicknesses improved bonding between layers and decreased the porosity of the parts. The laser scan speed has a significant effect on the densification behavior. The scan line spacing affects the pore structure by means of overlapping. The surface morphology of the samples was not affected by varying the scan line spacing. The ZrB2-CuNi electrodes presented a much superior performance than SLS copper powder electrodes, but inferior to solid copper electrodes.

Selective laser sintering of Mo-CuNi composite to be used as EDM electrode

Purpose – This work is focused on the investigation of direct production of electrical discharge machining (EDM) electrodes through the selective laser sintering (SLS) technique using a new metal-matrix composite material made of molybdenum and a copper-nickel alloy (Mo-CuNi). The influence and optimization of the main SLS parameters on the densification behavior and porosity is experimentally studied. Additionally, EDM experiments are performed to evaluate the electrodes performance under different machining conditions. The paper aims to discuss these issues. Design/methodology/approach – The new EDM electrode material used was a powder system composed of Mo and pre-alloyed CuNi. A systematic experimental methodology was designed to evaluate the effects of layer thickness, laser scan speed and hatch distance. The densification behavior, porosity and surface morphology of the samples were analyzed through microstructural and surface analysis. EDM experiments were conducted under three different regimes in order to observe the electrodes behavior and performance. The results were compared with copper powder electrodes manufactured by SLS and solid copper electrodes EDMachined under the same conditions. Findings – The experimental results showed that the direct SLS manufacturing of composite electrodes is feasible and an adequate combination of parameters can produce parts with good quality. The laser scan speed has a great effect on the densification behavior of the samples, while the effect of hatch distance on the porosity is more visible when the overlapping degree is considered. The overlapping also had a significant effect on the surface morphology. The EDM results showed that the Mo-CuNi electrodes had superior performance to the copper powder electrodes made by SLS for all the EDM regimes applied, but inferior to those achieved with solid copper electrodes. Originality/value – Significant results on the direct SLS manufacturing of a new material which has a great technological potential to be used as an EDM electrode material are presented. Valuable guidelines are given in regard to the SLS optimization of Mo-CuNi material and its performance as an EDM electrode. This work also provides a systematic methodology designed to be applied to the SLS process to produce EDM electrodes.

A study on the SLS manufacturing and experimenting of TiB2-CuNi EDM electrodes

Purpose – This work aims to investigate the direct production of electrical discharge machining (EDM) electrodes by means of the selective laser sintering (SLS) technique using a new non-conventional metal-matrix composite material (TiB2-CuNi). The influence and optimization of the main SLS parameters on the densification behavior and porosity is experimentally studied. EDM experiments are also performed to evaluate the electrodes performance. Design/methodology/approach – The new EDM electrode material used was a powder system composed of TiB2 and CuNi. Making use of a designed systematic experimental methodology, the effects of layer thickness, laser scan speed and scan line spacing were optimized, where aspects such as densification behavior, porosity and surface morphology of the samples were analyzed through microstructural and surface analysis. EDM experiments were conducted under three different regimes in order to observe the electrodes behavior and performance. The results were compared with copper powder electrodes manufactured by SLS and EDMachined under the same conditions. Findings – The experimental results showed that the direct SLS manufacturing of composite electrodes is feasible and promising. The laser scan speed has a high effect on the densification behavior of the samples, while the effect of scan line spacing on the porosity is more visible when the overlapping degree is considered. Surface morphology was not affected by the scan line spacing, whereas balling phenomenon was reported, regardless of the scan line spacing. The EDM results showed that the TiB2-CuNi electrodes had a much superior performance than the copper powder electrodes made by SLS, regardless of the EDM regime applied. Research limitations/implications – Generally, the machine tool itself promotes some restrictions to the SLS process optimization. It is normally attributed to the characteristics of the laser type and the amount of energy that can be delivered to the powder bed. The present investigation could not cover all the optimization potential involved with the studied material due to limitations of the SLS machine tool used. Originality/value – Significant results on the direct SLS manufacturing of a new non-conventional composite material, which has a great technological potential to be used as an EDM electrode material, are presented. Valuable guidelines are given in regard to the SLS optimization of TiB2-CuNi material and its performance as an EDM electrode. This work also provides a systematic methodology designed to be applied to the SLS process to produce EDM electrodes.

Additive manufacturing of zirconia parts by indirect selective laser sintering

Thermally induced phase separation (TIPS) was used to produce spherical polypropylene–zirconia composite powder for selective laser sintering (SLS). The influence of the composition of the composite starting powder and the SLS parameters on the density and strength of the composite SLS parts was investigated, allowing realizing SLS parts with a relative density of 36%. Pressure infiltration (PI) and warm isostatic pressing (WIPing) were applied to increase the green density of the ZrO 2 –PP SLSed parts. Infiltrating the SLS parts with an aqueous 30 vol.% ZrO 2 suspension allowed to increase the sintered density from 32 to 54%. WIPing (135 °C and 64 MPa) of the SLS and SLS/infiltrated complex shape green polymer–ceramic composite parts prior to debinding and sintering allowed raising the sintered density of the 3 mol Y 2 O 3 stabilized ZrO 2 parts to 92 and 85%, respectively.

Polystyrene‐coated alumina powder via dispersion polymerization for indirect selective laser sintering applications

AbstractA promising method for the manufacture of complex 3D ceramic parts is selective laser sintering (SLS). SLS of alumina components can be done either directly or indirectly. In this article, the indirect method is used by using polystyrene coated alumina particles. One of the methods to produce these alumina powders is dispersion polymerization. In this research, it is described how the alumina powder has been developed and tested. The powder has been characterized to define its processability within the SLS process. Used techniques include SEM (morphology), STA/TGA (overall mass loss), DSC (glass transition temperature Tg), and laser diffraction (particle size distribution). The investigated SLS process parameters were the preheating temperature, laser power, scan spacing, and scan speed. STA/TGA has proven that polystyrene‐coated alumina powders are suitable for SLS process, while DSC results were judged to be a good source of complementary data on preheating temperature of alumina/polystyrene powders. SLS experiments showed that single layer green parts can be produced. By using the optimized SLS parameters, it was demonstrated that different 3D geometries can be produced with the polystyrene coated alumina powders. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Isostatic pressing assisted indirect selective laser sintering of alumina components

PurposeThe purpose of this paper is to assess a new powder metallurgy process to make alumina parts through indirect selective laser sintering (SLS). Density measurements, some geometrical assessments and scanning electron microscopy (SEM) microstructural analyses are performed after each stage of the process, allowing an objective overview to be provided of the challenges and possibilities for the processing of high density technical ceramic parts through SLS of ball milled alumina/polyamide powder agglomerates.Design/methodology/approachThe powder production by ball milling, SLS, cold isostatic pressing (CIP) or quasi isostatic pressing (QIP), debinding and sintering (FS) stages of the powder metallurgy process were sequentially investigated.FindingsAlumina parts with a density up to 94.1 per cent could be produced by a powder metallurgy process containing an SLS step. Microstructural investigation of the sintered samples reveals an alumina matrix with a grain size of ∼5 μm and two different kinds of pore morphologies, i.e. long elongated pores, which stem from the intergranular spacings during SLS, and intermediate pores, which likely originate from larger polyamide agglomerates in the ball milled powder. Also, QIPing at elevated temperatures is found to be a promising alternative for CIPing at room temperature to increase the final part density.Research limitations/implicationsCracks, long elongated pores and intermediate pores remained in the sintered parts. Homogenizing the microstructure of the parts through optimizing the composite starting powder, the deposition during SLS, the SLS parameters and QIPing parameters is essential to overcome these limitations.Practical implicationsHomogenizing the starting powder mixture and the microstructure of the SLS material is the key issue for producing ceramic parts through indirect SLS.Originality/valueIndirect SLS of ceramics has hardly been reported and the combined use of SLS and QIPing is innovative in the field of indirect SLS of ceramics.

The effects and interactions of fabrication parameters on the properties of selective laser sintered hydroxyapatite polyamide composite biomaterials

PurposeHydroxyapatite‐polymer composite materials are being researched for the development of low‐load bearing implants because of their bioactive and osteoconductive properties, while avoiding modulus mismatch found in homogenous materials. For the direct production of hydroxyapatite‐polymer composite implants, selective laser sintering (SLS) has been used and various parameters and their effects on the physical properties (micro and macro morphologies) have been investigated. The purpose of this paper is to identify the most influential parameters on the micro and macro pore morphologies of sintered hydroxyapatite‐polymer composites.Design/methodology/approachA two‐level full factorial experiment was designed to evaluate the effects of the various processing parameters and their effects on the physical properties, including open porosity, average pore width and the percentage of pores which could enable potential bone regeneration and ingrowth of the sintered parts. The density of the sintered parts was measured by weight and volume; optical microscopy combined with the interception method was used to determine the average pore size and proportion of pores suitable to enable bone regeneration.FindingsIt was found that the effect of build layer thickness was the most influential parameter with respect to physical and pore morphology features. Consequently, it is found that the energy density equation with the layer thickness parameter provides a better estimation of part porosity of composite structures than the energy density equation without the layer thickness parameter. However, further work needs to be conducted to overcome the existing error of variance.Originality/valueThis work is the first step in identifying the most significant SLS parameters and their effects on the porosity, micro and macro pore morphologies of the fabricated parts. This is an important step in the further development of implants which may be required.

Optimized fabrication of Ca–P/PHBV nanocomposite scaffolds via selective laser sintering for bone tissue engineering

Biomaterials for scaffolds and scaffold fabrication techniques are two key elements in scaffold-based tissue engineering. Nanocomposites that consist of biodegradable polymers and osteoconductive bioceramic nanoparticles and advanced scaffold manufacturing techniques, such as rapid prototyping (RP) technologies, have attracted much attention for developing new bone tissue engineering strategies. In the current study, poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) microspheres and calcium phosphate (Ca–P)/PHBV nanocomposite microspheres were fabricated using the oil-in-water (O/W) and solid-in-oil-in-water (S/O/W) emulsion solvent evaporation methods. The microspheres with suitable sizes were then used as raw materials for scaffold fabrication via selective laser sintering (SLS), which is a mature RP technique. A three-factor three-level complete factorial design was applied to investigate the effects of the three factors (laser power, scan spacing, and layer thickness) in SLS and to optimize SLS parameters for producing good-quality PHBV polymer scaffolds and Ca–P/PHBV nanocomposite scaffolds. The plots of the main effects of these three factors and the three-dimensional response surface were constructed and discussed. Based on the regression equation, optimized PHBV scaffolds and Ca–P/PHBV scaffolds were fabricated using the optimized values of SLS parameters. Characterization of optimized PHBV scaffolds and Ca–P/PHBV scaffolds verified the optimization process. It has also been demonstrated that SLS has the capability of constructing good-quality, sophisticated porous structures of complex shape, which some tissue engineering applications may require.

Encapsulation and release of biomolecules from Ca–P/PHBV nanocomposite microspheres and three-dimensional scaffolds fabricated by selective laser sintering

This study focused on the fabrication of calcium phosphate (Ca–P)/poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanocomposite scaffolds loaded with biomolecules using the selective laser sintering (SLS) technique and their evaluation. Ca–P/PHBV nanocomposite microspheres loaded with bovine serum albumin (BSA) as the model protein were fabricated using the double emulsion solvent evaporation method. The encapsulation efficiency of BSA in PHBV polymer microspheres and Ca–P/PHBV nanocomposite microspheres were 18.06 ± 0.86% and 24.51 ± 0.60%, respectively. The BSA loaded Ca–P/PHBV nanocomposite microspheres were successfully produced into three-dimensional porous scaffolds with good dimensional accuracy using the SLS technique. The nanocomposite microspheres served as protective carriers and maintained the bioactivity of BSA during SLS. The effects of SLS parameters such as laser power and scan spacing on the encapsulation efficiency of BSA in the scaffolds and in vitro BSA release were studied. An initial burst release was observed, which was followed by a slow release of BSA. After 28-day release, The PHBV matrix was slightly degraded after 28-day in vitro release study. It was shown that nanocomposite scaffolds with controlled architecture obtained via SLS could be incorporated with biomolecules, enhancing them with more functions for bone tissue engineering application or making them suitable for localized delivery of therapeutics.

Processing and mechanical properties of porous 316L stainless steel for biomedical applications

Highly porous 316L stainless steel parts were produced by using a powder metallurgy process, which includes the selective laser sintering(SLS) and traditional sintering. Porous 316L stainless steel suitable for medical applications was successfully fabricated in the porosity range of 40%-50% (volume fraction) by controlling the SLS parameters and sintering behaviour. The porosity of the sintered compacts was investigated as a function of the SLS parameters and the furnace cycle. Compressive stress and elastic modulus of the 316L stainless steel material were determined. The compressive strength was found to be ranging from 21 to 32 MPa and corresponding elastic modulus ranging from 26 to 43 GPa. The present parts are promising for biomedical applications since the optimal porosity of implant materials for ingrowths of new-bone tissues is in the range of 20%-59% (volume fraction) and mechanical properties are matching with human bone.

Development of a 95/5 poly(L‐lactide‐co‐glycolide)/hydroxylapatite and β‐tricalcium phosphate scaffold as bone replacement material via selective laser sintering

95/5 Poly(L-lactide-co-glycolide) was investigated for the role of a porous scaffold, using the selective laser sintering (SLS) fabrication process, with powder sizes of 50-125 and 125-250 microm. SLS parameters of laser power, laser scan speed, and part bed temperature were altered and the degree of sintering was assessed by scanning electron microscope. Composites of the 125-250 microm polymer with either hydroxylapatite or hydroxylapatite/beta-tricalcium phosphate (CAMCERAM II were sintered, and SLS settings using 40 wt % CAMCERAM II were optimized for further tests. Polymer thermal degradation during processing led to a reduction in number and weight averaged molecular weight of 9% and 12%, respectively. Compression tests using the optimized composite sintering parameters gave a Young's modulus, yield strength, and strain at 1% strain offset of 0.13 +/- 0.03 GPa, 12.06 +/- 2.53 MPa, and 11.39 +/- 2.60%, respectively. Porosity was found to be 46.5 +/- 1.39%. CT data was used to create an SLS model of a human fourth middle phalanx and a block with designed porosity was fabricated to illustrate the process capabilities. The results have shown that this composite and fabrication method has potential in the fabrication of porous scaffolds for bone tissue engineering.

Selective laser sintering characteristics of nylon 6/clay-reinforced nanocomposite

Sintering characteristics and thermal properties of neat polyamide 6 and clay nanoparticle/polyamide 6 composite were compared for applications in the selective laser sintering (SLS) process. Differences in thermal and rheological behavior between the nanocomposite and the standard polymer were studied by differential scanning calorimeter, melt flow index, and compact sintering experiments. Nanoparticles increase the material’s viscosity and its mechanical properties. Sintered nanocomposite powders showed lower final density than the standard polymer due to increased resistance to low shear rate deformation. Because of this flow resistance, SLS parameters such as holding temperature and laser power must be adjusted and it may be impractical to improve rapidly manufactured part strength using such materials.