Improving accuracy through shrinkage modelling by using Taguchi method in selective laser sintering

Fabrication of porous polyvinyl alcohol scaffold for bone tissue engineering via selective laser sintering

Direct Metal Laser Sintering (DMLS) is a net shape fabrication technology that has been developed especially to fulfill the requirements of rapid tooling. The most important factors for successful rapid tooling are: 1) accuracy, 2) surface quality, 3) material properties and 4) speed. Surface quality has been the major concern for development work because rapid tooling applications require very smooth surfaces and finishing work is often needed. The quality of all surfaces can be greatly improved by reducing layer thickness and adjusting optimal scanning parameters in the DMLS process. Simultaneously stair-stepping effect can be minimized and almost faded out. Straightforward progress to smaller layer thickness has required material development work of finer metal powders and intensive research work for optimal laser processing. Simultaneously part building strategies have become more intelligent. It has been proved in practical cases that even 20 µm thin layers can be used for building steel parts with superior surface quality.This paper describes some of the key features for Direct Metal Laser Sintering of very fine metal powders. Latest results and experiences of research and development team at Rapid Product Innovations (formerly Electrolux Rapid Development) are discussed.Direct Metal Laser Sintering (DMLS) is a net shape fabrication technology that has been developed especially to fulfill the requirements of rapid tooling. The most important factors for successful rapid tooling are: 1) accuracy, 2) surface quality, 3) material properties and 4) speed. Surface quality has been the major concern for development work because rapid tooling applications require very smooth surfaces and finishing work is often needed. The quality of all surfaces can be greatly improved by reducing layer thickness and adjusting optimal scanning parameters in the DMLS process. Simultaneously stair-stepping effect can be minimized and almost faded out. Straightforward progress to smaller layer thickness has required material development work of finer metal powders and intensive research work for optimal laser processing. Simultaneously part building strategies have become more intelligent. It has been proved in practical cases that even 20 µm thin layers can be used for building steel parts with s...

Direct metal laser sintering (DMLS) is one of the methods in layer manufacturing technologies by which metal powder can be directly used to produce both prototype and production tools. The components manufactured by DMLS should have essential hardness for its application in the industry. This study was carried out to determine the optimum process parameters influencing the hardness of the components produced by DMLS. Sintering speed, hatch spacing, post contouring, infiltration and hatch type are the process parameters taken up for study. Statistical design of experiments using Taguchi’s orthogonal array was employed for this study. The experimental data obtained were analyzed using ANOVA. From the results, it is found that one of the process parameters; scan spacing affects the hardness of the parts produced by this technology to a significant extent.

To address the shortcomings of large porosity and insufficient mechanical properties of skeletonized Thermoplastic polyurethane (TPU) fabrications during the preparation of composite materials by selective laser sintering (SLS) technology. In this paper, SiO2@Si3N4ws‐GPTMS core‐shell structure filler was successfully prepared by first synthetically growing silicon dioxide (SiO2) nanospheres on the surface of silicon nitride whiskers (Si3N4ws) in situ by sol–gel method, and then modified with silane coupling agent Silane coupling agent (GPTMS). Then the filler was incorporated into the inner and outer surfaces of TPU skeletonized structural parts by vacuum dip coating using a water‐based polyurethane (PU) coating post‐treatment enhancement method, and the surface coating coating of TPU skeletonized structural parts was achieved by warming and curing. This composite filler coating structure greatly improved the mechanical properties of the SLS parts (tensile strength of 20.3 MPa and elongation at break of 338.9%, 163% higher tensile strength, 17.7% higher elongation at break, and 672% higher rebound dimension compared with the pure TPU sintered parts). In addition, the thermal stability of the SLS sintered parts was improved, which greatly enhanced the application of the sintered manufactured parts prepared by SLS technology in the field of rebound‐absorbing artificial wear.

Surface roughness of polyamide 12 parts manufactured using selective laser sintering

Features of obtaining bentonite-based ceramic support using SLS 3D printing

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.

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.

Finite Element Simulation of Heat Transfer in Laser Additive Manufacturing of AlSi10Mg Powders

Modeling and prediction of surface roughness and dimensional accuracy in SLS 3D printing of PVA/CB composite using the central composite design

Rapid Prototyping and Tooling (RP&T) technologies are applied extensively and intensively in the industry and their importance is increasing because it reduces the development time and cost required for product prototyping and injection moulding dies and EDM electrodes tooling. Namely additive technologies are getting interest due to the possibility to build a component by adding material. The paper addresses the study and application of Direct Metal Laser Sintering (DMLS) of copper alloys for Rapid Tooling of dies for thermoplastic polymer injection moulding. Specific samples have been designed by CAD, in order to be representative of the geometrical and morphological features and functional characteristics of the dies. The main limitations of DMLS prototypes are relevant to surface properties as porosity, roughness, hardness, corrosion, erosion and wear resistance. The study takes into consideration the characterization and improvement of DMLS surface properties in order to meet their functional requirements. To this purpose, different surface treatments have been studied and applied, as blasting and peening, resin infiltration, electroless nickel plating. Sample surfaces has been fully characterized and analysed, as obtained by DMLS, and after surface treatments. 3D surface roughness and microgeometrical morphology and porosity and microhardness properties have been systematically investigated.

This work presents the results of a study carried out to determine the reciprocating wear behavior and its effect on the process parameters of components manufactured by selective laser sintering (SLS). A standard procedure and specimen had been used in the present study to find the wear behavior. Using Taguchi’s experimental technique, an orthogonal array of modified L9 had been developed. Reciprocating wear testing was carried out and analysis of variance (ANOVA) technique was used to investigate the effect of process parameters and to identify the main process parameter that influences the properties of wear behavior on the SLS components. It has been found that laser power had more influence on wear as compared to other selected process parameters. Micro-structural analysis was also carried out using scanning electron microscope on the wear testing sample.

The abstract aims to investigate the comparative performance of Electrical Discharge Machining (EDM) and Selective Laser Sintering (SLS) with unconventional machining processes. Unconventional machining processes have gained significant attention due to their versatility and capability to fabricate intricate components with high precision. This study focuses on assessing the efficacy of EDM and SLS techniques in terms of data removal rate and relative wear volume. Electrical Discharge Machining (EDM) is a thermal erosion process that utilizes electrical discharges to remove material from a workpiece. In contrast, Selective Laser Sintering (SLS) is an additive manufacturing technique that employs a laser to selectively fuse powdered material, layer by layer, to build up a three-dimensional object. Both methods offer unique advantages in terms of precision, speed, and material compatibility. The performance evaluation of these techniques involves analyzing key parameters such as data removal rate, which measures the volume of material removed per unit time, and relative wear volume, which quantifies the wear on the tool or workpiece during the machining process. By comparing these metrics, insights into the efficiency and effectiveness of EDM and SLS can be gained, aiding manufacturers and researchers in selecting the most suitable method for specific applications. Through experimental investigations and data analysis, this study aims to provide valuable insights into the capabilities and limitations of EDM and SLS in unconventional machining processes. The findings will contribute to advancing the understanding of these techniques and optimizing their utilization in various industrial sectors, including aerospace, automotive, and biomedical engineering. The experimental analysis examines the impact of the Direct Metal Laser Sintering (DMLS) process parameter on sintering depth. The optimized parameters for AlSi10Mg alloy powder sintering were obtained using laser power at 162 W, scanning speed at 156 mm s−1, porosity at 20%, laser area size of 0.2 mm, and layer thickness of 1 mm.

Rapid manufacturing techniques are typically either material addition or material subtraction processes. Direct metal laser sintering (DMLS) is a material addition process that enables the rapid creation of complex parts via laser sintering (or electron beam melting) whereby layers of powder are deposited and then partially or totally melted using a laser. This technique is directly challenging other more rapid, but subtractive manufacturing processes like high-speed milling (HSM) and electro-erosion. In terms of machining, the capacity of rapid tooling to quickly manufacture complex shapes, like conformal cooling channels, is an advantage (Boillat in J Phys IV 12(Pr 11):27–38, 2002, Au in Int J Adv Manuf Technol 34:496–515, 2007). On the other hand, the dimensional accuracy of this process is definitely lower than that obtained using HSM. To our knowledge, no systematic study of the dimensional capacities of this process has yet been carried out. In this article, through the geometrical study of the quality of the obtained parts, the capability of this process is studied and verified with respect to the required constraints of the die casting method.

Preparation and laser sintering of limestone PA 12 composite