Selective Laser Sintering Method Research Articles

Prospects of Creating Products Using Selective Laser Sintering

At present, the development of techniques and technology can’t do without innovations in production. This explains the desire of mankind to look for innovative ways to produce different types of products. One of these systems is the production method of selective laser sintering. It is more promising as compared to other rapid prototyping techniques, due to the relative cheapness of materials and time-consuming to produce finished products. This article discusses the method of selective laser sintering, its advantages and disadvantages.

RESEARCH ON LASER MICRO POLISHING OF SLS TECHNOLOGY SINTERED IRON-BASED POWDER SURFACE / SELEKTYVIUOJU LAZERINIO SUKEPINIMO BŪDU SUKEPINTŲ GELEŽIES PAGRINDO MILTELIŲ PAVIRŠIAUS LAZERINIO MIKROAPDIRBIMO TYRIMAI

The article analyzes laser micro polishing of 1.2083 steel samples produced applying selective laser sintering (SLS) method. The study has evaluated the distribution of the shape, size and temperature of the laser beam treated area in the surface layer of sintered and laser polished samples. Experimental tests have shown the impact of the technical parameters of laser micro polishing on the width and hardness of the impact zone of the treated sample. The microstructure analysis of laser treated and untreated areas of the material has been made. Straipsnyje nagrinėjamas selektyviuoju lazerinio sukepinimo (SLS) būdu pagamintų plieno 1.2083 bandinių mikroapdirbimas lazerio pluoštu. Tyrimo metu įvertinta sukepintų ir lazeriu apdorotų bandinių poveikio zonos forma ir dydis bei temperatūros pasiskirstymas paviršiniame sluoksnyje. Eksperimentinių bandymų metu nustatyta lazerinio mikroapdirbimo technologinių parametrų įtaka apdoroto bandinio poveikio zonos pločiui ir kietumui. Buvo atlikta bandinių lazerio pluoštu paveiktų ir neapdorotų medžiagos zonų mikrostruktūros analizė.

Fabrication of Microhotplate by Selective Laser Sintering of Micropowder for Thermal Conductivity Measuring Sensors

The layout of experimental samples of microhotplate based on nanocomposite material consisting of ruthenium dioxide and borosilicate glass binder were formed by selective laser sintering method. The resulting structures were used as microhotplate to measure changes in thermal conductivity of gases. The comparison of power consumption of standard platinum wire coil element widely used in thermocatalytic (calorimetric) sensors and microhotplate produced by the new technology showed strong advantage of the latter one.

The Analysis of Laser Modification of the Surface of SLS Specimens

In the Paper, an analysis of laser modification of the surface of specimens produced of powder steel 1.2083 by SLS (selective laser sintering) method is carried out. Three main structures being formed on laser modification of the sintered steels are presented: periodical, interim and degrading. The dependence of the changes of the technological parameters of the laser equipment on the geometrical parameters of the specimen under processing is provided.

Fabrication of Microhater by Selective Laser Sintering of Ruthenium Dioxide Micropowder

During the topology creation by the selective laser sintering method experimental samples of microheater based on ruthenium dioxide micro-powder were made. The resulting structures were used as microheaters to measure changes in the thermal conductivity of gases. A power comparison of standard platinum spiral element widely used in catalytic thermal sensors and microheater produced by the new technology showed the advantage of the latter.

CFD and FEM Model of an Underwater Vehicle Propeller

Abstract Within the framework of the project for design and optimization of the Remotely Operated Vehicle (ROV), research on its propulsion has been carried out. Te entire project was supported by CFD and FEM calculations taking into account the characteristics of the underwater vehicle. One of the tasks was to optimize the semi-open duct for horizontal propellers, which provided propulsion and controllability in horizontal plane. In order to create a measurable model of this task it was necessary to analyze numerical methodology of propeller design, along with the structure of a propellers with nozzles and contra-rotating propellers. It was confronted with theoretical solutions which included running of the analyzed propeller near an underwater vehicle. Also preliminary qualitative analyses of a simplified system with contra-rotating propellers and a semi-open duct were carried out. Te obtained results enabled to make a decision about the ROVs duct form. Te rapid prototyping SLS (Selective Laser Sintering) method was used to fabricate a physical model of the propeller. As a consequence of this, it was necessary to verify the FEM model of the propeller, which based on the load obtained from the CFD model. Te article contains characteristics of the examined ROV, a theoretical basis of propeller design for the analyzed cases, and the results of CFD and FEM simulations.

The mechanical properties of the system tooth-cement-post made of Co-Cr alloy using the selective laser sintering method

The mechanical properties of the system tooth-cement-post made of Co-Cr alloy using the selective laser sintering method

Simulation of thermomechanical and electrothermal hysteresis phenomena in porous nickel titanium

There is represented a general scheme of functioning and the corresponding model of a porous biomicrofluid matrix based on nickel titanium, which possesses a shape-memory effect, prepared by the method of selective laser sintering. The simulation of thermomechanical and electrothermal hysteresis phenomena composes the basis of the functioning of this MEMS. Such a model can be used for estimating the efficiency and controllability of drug delivery systems via the change in the volume of pores.

Fabrication of hydrodynamic torque converter impellers by using the selective laser sintering method

Purpose – The main aim of the paper is the application of the selective laser sintering (SLS) method for fabrication of hydrodynamic torque converter (HTC) impellers. Design/methodology/approach – Establishing of assumptions for the impeller design process based on the HTC characteristics analysis, creation of the virtual solid model of HTC impellers, fabrication of HTC impellers by using the SLS method, investigation of the performance of HTC with fabricated impellers by using a test rig. Findings – The test results show that the SLS method can be successfully used for the fabrication of HTC impellers with 3D and flat blades. Research limitations/implications – The method application is limited to small diameters of HTC impellers depending on working area dimensions of SLS machine. Practical implications – The method can decrease the time and cost of fabrication of HTC impellers by using the SLS method. Originality/value – The application of the SLS method for fabrication of HTC impellers with 3D and flat blades.

OP114: Craniofacial bone reconstruction with a fiber-reinforced bioactive composite implant

Purpose Large skull bone defects cause both functional and aesthetic problems to the patients. A bioactive fiber reinforced composite is presented to address some of the problems faced in current options for craniofacial bone reconstruction. Synthetic, osteoconductive and antimicrobial, bioactive glass S53P4 (BAG) with E-glass fibers in a new custom made composite implant for craniofacial reconstructions. Soft tissue flap may be used if the primary wound healing is compromised. Material and methods Retrospective series of 27 patients has operated with craniofacial deformity during 2007–2012. The bone defects the consequence of craniotomies performed due to traumatic and spontaneous intra-cranial bleeding as well as infections to primary reconstruction materials. After the skull defect characterized with three-dimensional computer tomography, a rapid prototype model of the skull was made from polyamide with a selective laser sintering method. This model was then used to manufacture a customized implant. The implant material consisted of a supporting fiber-reinforced framework, porous inner layers and bioactive glass filling. The composite structure of the implant allowed the biomechanical excellence of the fiber-reinforced structure to be coupled with the properties of bioactive glass. Results The aesthetic and functional outcomes of all patients were good and patients were satisfactory for reconstructions. No infections, skin problems or hair growth distortions were reported. Normal progressive wound healing was observed in 26 cases out of 27. A microvascular flap reconstruction for a patient with non-optimal wound healing capacity is presented. Any other clinical complications were not observed. Conclusions Reconstruction of difficult skull defects with the novel bioactive composite implant is a promising solution compared to previously use conventional materials. A soft tissue flap or a microvascular flap may be used if needed.

A multi-level rapid prototyping drill guide template reduces the perforation risk of pedicle screw placement in the lumbar and sacral spine

The method of free-hand pedicle screw placement is generally safe although it carries potential risks. For this reason, several highly accurate computer-assisted systems were developed and are currently on the market. However, these devices have certain disadvantages. We have developed a method of pedicle screw placement in the lumbar and sacral region using a multi-level drill guide template, created with the rapid prototyping technology and have validated it in a clinical study. The aim of the study was to manufacture and evaluate the accuracy of a multi-level drill guide template for lumbar and first sacral pedicle screw placement and to compare it with the free-hand technique under fluoroscopy supervision. In 2011 and 2012, a randomized clinical trial was performed on 20 patients. 54 screws were implanted in the trial group using templates and 54 in the control group using the fluoroscopy-supervised free-hand technique. Furthermore, applicability for the first sacral level was tested. Preoperative CT-scans were taken and templates were designed using the selective laser sintering method. Postoperative evaluation and statistical analysis of pedicle violation, displacement, screw length and deviation were performed for both groups. The incidence of cortex perforation was significantly reduced in the template group; likewise, the deviation and displacement level of screws in the sagittal plane. In both groups there was no significantly important difference in deviation and displacement level in the transversal plane as not in pedicle screw length. The results for the first sacral level resembled the main investigated group. The method significantly lowers the incidence of cortex perforation and is therefore potentially applicable in clinical practice, especially in some selected cases. The applied method, however, carries a potential for errors during manufacturing and practical usage and therefore still requires further improvements.

Interactive presurgical simulation applying advanced 3D imaging and modeling techniques for skull base and deep tumors

In this paper, the authors' goal was to report their novel presurgical simulation method applying interactive virtual simulation (IVS) using 3D computer graphics (CG) data and microscopic observation of color-printed plaster models based on these CG data in surgery for skull base and deep tumors. For 25 operations in 23 patients with skull base or deep intracranial tumors (meningiomas, schwannomas, epidermoid tumors, chordomas, and others), the authors carried out presurgical simulation based on 3D CG data created by image analysis for radiological data. Interactive virtual simulation was performed by modifying the 3D CG data to imitate various surgical procedures, such as bone drilling, brain retraction, and tumor removal, with manipulation of a haptic device. The authors also produced color-printed plaster models of modified 3D CG data by a selective laser sintering method and observed them under the operative microscope. In all patients, IVS provided detailed and realistic surgical perspectives of sufficient quality, thereby allowing surgeons to determine an appropriate and feasible surgical approach. Surgeons agreed that in 44% of the 25 operations IVS showed high utility (as indicated by a rating of "prominent") in comprehending 3D microsurgical anatomies for which reconstruction using only 2D images was complicated. Microscopic observation of color-printed plaster models in 12 patients provided further utility in confirming realistic surgical anatomies. The authors' presurgical simulation method applying advanced 3D imaging and modeling techniques provided a realistic environment for practicing microsurgical procedures virtually and enabled the authors to ascertain complex microsurgical anatomy, to determine the optimal surgical strategies, and also to efficiently educate neurosurgical trainees, especially during surgery for skull base and deep tumors.

Final Manufacturing Process of Front Side Metallisation on Silicon Solar Cells Using Conventional and Unconventional Techniques

The paper presents the results of the investigation of the front electrode manufactured using two silver pastes (PV 145 manufactured by Du Pont and another based on nanopowder experimentally prepared) on monocrystalline silicon solar cells in order to reduce contact resistance. The aim of the paper was a comparison between a conventional and an unconventional method to improve the quality of forming electrodes of silicon solar cells. The Screen Printing (SP) method is the most widely used contact formation technique for commercial silicon solar cells. Selective Laser Sintering (SLS) is a modern manufacturing technique, which uses a high power CO2 laser to melt or sinter metal powder particles into a mass that has the desired three-dimensional shape, in precisely defined areas. The whole process is controlled by a program that is used for micro-processing. An innovative aspect of this method is the application of a nano silver paste to create the seed layer of the front electrode using the SLS method. The topography of both co-fired in the infrared belt furnace and melted/sintered in the Eosint M250 Xtended device equipped with CO2 laser were studied. Contacts were investigated using confocal laser scanning microscope (CLSM 5) and a scanning electron microscope (SEM) with an energy dispersive X-ray (EDS) spectrometer for microchemical analysis. Both surface topography and a cross section of the front electrodes were studied using SEM microscope. Phase composition analyses of the chosen front electrodes were done using the XRD method delineated in this paper. Front electrodes were formed on the surface with a different morphology from the solar cells. The median size of the pyramids was measured using the atomic force microscope (AFM). Resistance of the front electrodes was measured using the Transmission Line Model (TLM).

Evaluation of the marginal and internal gap of metal-ceramic crown fabricated with a selective laser sintering technology: two- and three-dimensional replica techniques

PURPOSEOne of the most important factors in evaluating the quality of fixed dental prostheses (FDPs) is their gap. The purpose of this study was to compare the marginal and internal gap of two different metal-ceramic crowns, casting and selective laser sintering (SLS), before and after porcelain firing. Furthermore, this study evaluated whether metal-ceramic crowns made using the SLS have the same clinical acceptability as crowns made by the traditional casting.MATERIALS AND METHODSThe 10 study models were produced using stone. The 20 specimens were produced using the casting and the SLS methods; 10 samples were made in each group. After the core gap measurements, 10 metal-ceramic crowns in each group were finished using the conventional technique of firing porcelain. The gap of the metal-ceramic crowns was measured. The marginal and internal gaps were measured by two-dimensional and three-dimensional replica techniques, respectively. The Wilcoxon signed-rank test, the Wilcoxon rank-sum test and nonparametric ANCOVA were used for statistical analysis (α=.05).RESULTSIn both groups, the gap increased after completion of the metal-ceramic crown compared to the core. In all measured areas, the gap of the metal cores and metal-ceramic crowns produced by the SLS was greater than that of the metal cores and metal-ceramic crowns produced using the casting. Statistically significant differences were found between cast and SLS (metal cores and metal-ceramic crown).CONCLUSIONAlthough the gap of the FDPs produced by the SLS was greater than that of the FDPs produced by the conventional casting in all measured areas, none exceeded the clinically acceptable range.

Simulation of transient temperature for mixture of two materials in the selective laser sintering process

In the process of rapid prototyping by the method of selective laser sintering, transient temperature has a direct effect upon the sintering performance. In the present work, a model is developed to predict the three-dimensional transient temperature field. It uses the finite element method to model the variation of thermal properties and solid–liquid two-phase interface in sintering the mixture of Al2O3-coated ceramic powder and polystyrene powder. A high-speed charge-coupled device image temperature measurement system is used to obtain real data from laser sintering experiments for comparison. The test results validate the simulation data and imply that the modelling method is useful in predicting the transient sintering temperature when correct thermal properties and key factors of two-phase interface are main concerns. The performance characteristics of the sintering process are predicted by the modelling method.

3D modeling and testing of transient temperature in selective laser sintering (SLS) process

In the process of rapid prototyping by the method of selective laser sintering (SLS), transient temperature has direct effect upon the sintering performance. In the present work, a model is developed in order to generate 3D transient temperature field. It uses Al2O3 coated ceramic powder and involves the finite element method (FEM) variation of thermal properties and solid–liquid two-phase interface. A high-speed charge coupled device (CCD) image temperature measurement system is used to generate for testing. The obtained test results validates the simulation data and implies that the proposed modeling method is useful in simulating the transient sintering temperature specially when the correct thermal properties and key factors of two-phase interface are main concerns. The performance characteristics of the reasonable sintering parameters are predicted by the proposed modeling method.

Functional design of porous drug delivery systems based on laser assisted manufactured nitinol

ABSTRACTOur previous studies proved the occurrence of the shape memory effect (SME) in a biocompatible porous nitinol (inter-metallic phase NiTi), obtained by the selective laser sintering (SLS) method. In this report we propose to use the SME peculiar to the nitinol, for a functional design of the drug delivery system and to discuss the process flow pattern. In living tissues (flesh) the elevated temperature at the disease origination leads to the nitinol pores size reduction caused by the austenite phase transformation, and to the pharmaceutical composition extrusion from the pores. And vice versa, during the cooling stage when the tissue temperature reverts to normal level, the drug intake will stop. Depending on the type of the three dimensional structure of a porous matrix (scaffold) identified at the stage of a computer-aid-design, the velocity of penetration can be controllable.

MMSSC Chemotaxis near Porous Surface of Biocompatible NiTi Scaffolds Synthesized by Selective Laser Sintering (SLS)

ABSTRACTMultipotential mesenchymal stromal stem cells (MMSSC) are an excellent model for testing of the toxicity and biocompatibility of natural-tissue-engineering scaffolds (extracellular matrix). Such studies allow prediction of the behavior of implanted materials in the human. In the present work, testing of a three-dimensional prototype of a smart material – nitinol (the intermetallic phase NiTi) – to evaluate chemotaxis and biocompatibility was conducted.Porous samples were synthesized by the selective laser sintering (SLS) method, establishing different surface conditions in the samples. The surface microstructure and roughness were observed by scanning electron microscopy (SEM) and optical microscopy. The results revealed the clear influence of the surface roughness on stem cell proliferation, morphology, and adhesion. The NiTi samples were well tolerated by the cells but the number of focal contacts decreased with increasing porosity. The proliferation speed was 0.694 doubling/day in the control group and 0.532 doubling/day for the NiTi group. Whereas the control group showed immature and actively divided stem cells, cell growth to enormous sizes (i.e., rapid aging) and a fall in fission activity in the proximity of an external irritant (viz., the NiTi scaffold) was observed.

Plastic forming simulations of cold isostatic pressing of selective laser sintered components

A combined method of selective laser sintering (SLS) and cold isostatic pressing (CIP) was applied to manufacturing metal parts rapidly. Finite element method was used to predict final dimensions and decrease cost. The simulations of CIP of selective laser sintered parts were carried out by Drucker-Prager-Cap constitutive model with ABAQUS computer program. The property of metal powder was measured by CIP experiments. The results show the rubber bag and the friction coefficient have little influence on results of simulations. The parts only have uniform shrinkage and have no obvious distortion in shape. The results of simulations show a good agreement with the experimental results and the calculated results, indicating that the Drucker-Prager-Cap model is an effective model to simulate CIP process. The simulations could give a useful direction to forming process of the CIP of selective laser sintered components.

Biocompatibility of Tissue Engineering Constructions from Porous Polylactide Carriers Obtained by the Method of Selective Laser Sintering and Bone Marrow-Derived Multipotent Stromal Cells

We studied the biocompatibility of porous polylactide carrier matrices obtained by means of surface selective laser sintering. Carrier matrices had no cytotoxic activity, but maintained adhesion and proliferation of cells. Subcutaneous transplantation of tissue engineering constructions from these carriers and bone marrow-derived multipotent stromal cells did not cause the inflammatory response and pathological changes in rats. The conditions for organotypic regeneration were provided at the site of transplantation (high degree of blood supply and considerable amount of immature precursor cells).