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Lightweighting with adequate mechanical strength is one of the key objectives of Industry 4.0. Replacement of solid parts with cellular lattice structured ones is one of the alternatives to elevate performance and reduce weight, without harming sustainability and carbon neutrality goals. Lattice structured parts possess several loads including tensile as the main type of loading; however, few researchers have studied the tensile response of mechanical metamaterials. This study aims to investigate the structural properties under tensile loading of four different types of mechanical metamaterials (simple cubic, octet, face-centered cubic, and body-centered cubic) fabricated using a selective laser sintering process using polyamide material. X-ray computed tomography was employed to examine the manufacturability of strut-based structures. Effects of relative densities, material distribution, deformation behavior, and fracture of structures on mechanical responses of each structure were evaluated at various relative densities of 40%, 50%, and 60%. Results exhibit that octet and FCC structures possess more elongation at higher relative densities compared to lower relative densities of the same structures. In addition, these structures fractured in a brittle manner at lower (40%) relative densities and this trend changes from brittle to ductile at higher relative density (60%). SC structure performed best (848 N) but the BCC (348 N) is worst at constant relative density (40%); thus, performance is significantly different due to different structure morphologies. The orientation of struts has a significant effect on the tensile loading of lattice structures. The structures having zero inclined struts fractured significantly different manner compared to their counterparts having inclined struts. The octet structure is considered to have a greater amount of elongation in the tensile direction while the SC structure has the highest load-bearing capacity. [ABSTRACT FROM AUTHOR]

AbstractThe development of gastroretentive drug delivery systems is one such instance, which was developed to improve the oral bioavailability and effectiveness of drugs, which has a poor absorption window in the upper GIT and/or triggers local activity such as duodenal and stomach activity. In this work, the objective of sintering gastroretentive dosage forms was to sustain the release of levofloxacin in the gastric region for an extended period of time. Selective laser sintering (SLS)-mediated powder bed fusion 3D printing technology was utilized to design and fabricate a modified-release gastroretentive floating-hollow capsular device (GRF-HCD) in three distinct capsule sizes namely, 000, 00, and 0 with the aid of pharmaceutical grade polymers (combinations of Kolliphor P188 and Kollidon SR in 1:1 ratio). Sintered GRF-HCD was further subjected to morphological analysis, weight variation, and swelling index. In addition, in vitro and in vivo buoyancy studies were performed in an animal model using X-ray imaging. Finally, the in vitro drug release from GRF-HCD was performed in simulated gastric pH condition (pH-1.2) upto 12 h. Levofloxacin concentration was then quantified using validated RP-HPLC method. The in vitro floating behaviour was mimicked with the in vivo floating, where the GRF-HCD was retained in the rabbit stomach for an extended period which will help to sustain the drug release for a longer period and maintained the maximum concentration of levofloxacin in the gastric region. [ABSTRACT FROM AUTHOR]

This study describes procedures for embedding digital information into additively manufactured components as well as procedures for readout and tensile testing. Embedded digital codes were printed inside ASTM E8/E8M dumbbells using Direct Metal Laser Melting (DMLS) with an EOS M290 printer. The codes were configured as either ellipsoids or prolate spheroids in patterns given by the Cantor dust fractal. Tensile testing was performed on 15 dumbbells, 7 with digital codes in the gauge volume and 8 with codes in the dumbbell tail. Results showed that the dumbbells met the ultimate tensile strength specification for the EOS AlF357 powder. X-ray imaging, both conventional and interferometry, was explored to detect the digital information. X-ray tomography showed measured ellipsoid volumes slightly larger than as-designed ellipsoid volumes, even when partially filled with loose powder. X-ray interferometry showed increased void detectability, one advantage of loose powder. These results suggest a standard selective laser sintering printer with typical metal powders could reasonably expect to print 100 bits of embedded digital information in a gauge volume 6 mm in diameter as 300 m voids while still maintaining tensile specifications. [ABSTRACT FROM AUTHOR]

AbstractHoneycomb materials are considered ultra-light materials with excellent mechanical properties due to their unique cellular structure. Their high strength, low density, and excellent energy-absorbing abilities have led to their widespread application in various fields. The star cellular structure is a classical cellular structure proposed by many scholars, exhibiting a negative Poisson’s ratio effect. However, due to the susceptibility of the star-shaped units and the vertical supporting rods at the joints to local instability and stress concentration under compressive loads, the buckling of the supporting rods can induce lateral displacement, thereby compromising the overall structural integrity and performance. To address this phenomenon, this study eliminates the supporting rods from the star-shaped structure, specimens of the Improved Star-Shaped Honeycomb (ISSH) were fabricated using Selective Laser Sintering (SLS) technology, followed by uniaxial quasi-static compression experiments and finite element simulations, followed by uniaxial quasi-static compression experiments and finite element simulations. The study investigates whether changes in geometric parameters can enhance the tunability of the structure for different application scenarios. The results reveal that the rod-free star-shaped structure exhibits higher stiffness and strength, and variations in wall thickness and angular parameters significantly influence the structural performance and deformation failure mechanisms. This study enriches the research on star-shaped honeycomb structures. [ABSTRACT FROM AUTHOR]

Selective laser sintering (SLS) is one of the prominent methods of polymer additive manufacturing (AM). A low-power laser source is used to directly melt and sinter polymer material into the desired shape. This study focuses on the utilization of the low-power laser SLS system to successfully manufacture metallic components through the development of a metal–polymer composite material. In this study, 17-4 PH stainless powders are used and mixed with polyoxymethylene (POM) and high-density polyethylene (HDPE) to prepare the composite powder material. The polymeric mixture is removed during the thermal degreasing process and subsequent sintering results in a solid metallic component. Sinterit Lisa with a 5 W, 808 nm laser source is used to fabricate the green part. For the printing parameters of 140 °C, laser power of 35.87 mJ/mm2, and layer thickness of 100 μm, the printed samples achieved a maximum density of 3.61 g/cm3 and a complete shape. After sintering at 1310 °C for 180 min, the tensile strength of the shrunk sample is 605.64 MPa, the hardness is HRC 14.8, the average shrinkage rate is 22%, and the density is 7.57 g/cm3, which can reach 97% of the theoretical density. This process allows the use of a wide range of particle sizes that the usual AM technologies have, making it a low-cost, low-energy-consumption, high-speed AM technology. [ABSTRACT FROM AUTHOR]

Highlights In the present work, Graphite nanoPlatelets/Polyamide‐12 (GnPs/PA‐12) particle composites were produced through additive manufacturing (AM). The selective laser sintering (SLS) technology was used to manufacture 3D‐printed composite components by means of a powder mix of GnPs and PA‐12. The analyzed combination of technology and materials allows to obtain parts with improved thermal, electrical, and tribological properties, while maintaining a low production cost. In total were realized 5 different scenarios, each one with a different wt% of the GnPs reinforcement (2‐4‐6‐8‐10 wt%), and compared the results to the PA‐12 matrix. Experimental tests were performed to study the morphology (profilometry, SEM, wettability), the electrical conductivity under different normal loads (0.1–1 kN), the thermal performance, and the tribological properties of each sample. The results show that the increase of GnPs particles dispersed in the matrix leads to a hydrophobic behavior of the surface. An improvement in electrical conductivity (from 10−11 S/cm of the pure PA‐12 matrix to 10−4 S/cm of the 10 wt% GnPs) and thermal performance (33,6% improvement for the best‐case scenario compared to the bare matrix) was observed. Tribological tests underlined a reduction of 25% in friction coefficient and an improvement of 80% in wear resistance compared to the PA‐12 matrix. 3D printed GnPs/PA‐12 composites does not exhibit any significant geometrical alteration. GnPs enable hydrophobic surfaces with increased contact angles. Electrical conductivity improved from 10−11 S/cm of the unfilled PA‐12 matrix up to 10−4 S/cm, for the 10 wt% GnPs sample. Thermal performance improves up to 33.6% with GnPs reinforcement. 10 wt% GnPs reduces friction by 25% and wear by 81%. [ABSTRACT FROM AUTHOR]

In order to enhance the mechanical properties of lattice structure parts made of thermoplastic polyurethane elastomer (TPU) prepared by selective laser sintering (SLS) technology, this study employed the oxidative self‐polymerization of dopamine (DA) to prepare polydopamine‐modified silicon carbide whiskers (PDA‐SiC) fillers with a core‐shell structure. These fillers were uniformly dispersed in a waterborne polyurethane (WPU) to form a coating solution, which was then used to prepare TPU printed parts with a uniform PDA‐SiC/WPU coating structure through post‐treatment impregnating‐curing processes. The coated TPU parts exhibited tensile strength, elongation at break, and room temperature compressive strength of 8.37 MPa, 610.2%, and 1.062 MPa, respectively, representing improvements of 40.9%, 33.2%, and 353.3% compared to pure TPU parts. This approach effectively enhanced the mechanical performance of SLS‐formed TPU parts, strengthening their application in the field of flexible lattice structure parts. [ABSTRACT FROM AUTHOR]

The current research aims to analyze the shape and structural features of the eggs of the lepidoptera species Melitaea sp. (Lepidoptera, Nympalidae) and develop design solutions through the implementation of a novel strategy of biomimetic design. Scanning electron microscopy (SEM) analysis of the chorion reveals a medial zone that forms an arachnoid grid resembling a ribbed dome with convex longitudinal ribs and concave transverse ring members. A parametric design algorithm was created with the aid of computer-aided design (CAD) software Rhinoceros 3D and Grasshopper3D in order to abstract and emulate the biological model. A series of physical models were manufactured with variations in geometric parameters like the number of ribs and rings, their thickness, and curvature. Selective laser sintering (SLS) technology and Polyamide12 (nylon) material were utilized for the prototyping process. Quasi-static compression testing was carried out in conjunction with finite element analysis (FEA) to investigate the deformation patterns and stress dispersion of the models. The biomimetic ribbed dome appears to significantly dampen the snap-through behavior that is observed in typical solid and lattice domes, decreasing dynamic stresses developed during the response and preventing catastrophic failure of the structure. Increasing the curvature of the ring segments further reduces the snap-through phenomenon and improves the overall strength. However, excessive curvature has a negative effect on the maximum sustained load. Increasing the number and thickness of the transverse rings and the number of the longitudinal ribs also increases the strength of the dome. However, excessive increase in the rib radius leads to more acute snap-through behavior and an earlier failure. The above results were validated using respective finite element analyses. [ABSTRACT FROM AUTHOR]

Background/Objectives: Selective laser sintering (SLS) is one of the most promising 3D printing techniques for pharmaceutical applications as it offers numerous advantages, such as suitability to work with already approved pharmaceutical excipients, the elimination of solvents, and the ability to produce fast-dissolving, porous dosage forms with high drug loading. When the powder mixture is exposed to elevated temperatures during SLS printing, the active ingredients can be converted from the crystalline to the amorphous state, which can be used as a strategy to improve the dissolution rate and bioavailability of poorly soluble drugs. This study investigates the potential application of SLS 3D printing for the fabrication of tablets containing the poorly soluble drug carvedilol with the aim of improving the dissolution rate of the drug by forming an amorphous form through the printing process. Methods: Using SLS 3D printing, eight tablet formulations were produced using two different powder mixtures and four combinations of experimental conditions, followed by physicochemical characterization and dissolution testing. Results: Physicochemical characterization revealed that at least partial amorphization of carvedilol occurred during the printing process. Although variations in process parameters were minimal, higher temperatures in combination with lower laser speeds appeared to facilitate a greater degree of amorphization. Ultimately, the partial conversion to the amorphous form significantly improved the dissolution of carvedilol compared to its pure crystalline form. Conclusions: Obtained results suggest that the SLS 3D printing technique can be effectively used to convert poorly water-soluble drugs to their amorphous state, thereby improving solubility and bioavailability. [ABSTRACT FROM AUTHOR]

Lattice metamaterials have gained considerable attention due to their distinctive topological structures and multifunctional properties. In this work, the effect of topology, loading conditions, and relative density on the effective mechanical properties of various novel lattice architectures is investigated numerically and experimentally. Thirteen strut-based lattices derived from triply periodic minimal surfaces (five lattices) as well as Platonic (three lattices) and Archimedean (five lattices) solids are considered for the first time, and their anisotropic mechanical properties, including uniaxial, shear, and bulk moduli and strengths as well as their total stiffness, buckling strengths, Poisson's ratio, and anisotropy are investigated as a function of a wide range of relative densities (0.1% to 37%). Finite element analysis is employed to capture the full effective behavior of these lattices using periodic boundary conditions. Bifurcation analysis is performed to predict the threshold relative density governing their buckling vs yielding deformation behavior. Selected lattice structures of various relative densities are 3D printed using polymer selective laser sintering additive manufacturing technique and tested under quasi-static uniaxial compression where the experimental and numerical results are compared. The numerical results indicate that the deformation behavior can be altered between stretching and bending dominated mode of deformation as function of loading. Archimedean lattices are shown to outperform a wide range of strut-based lattices. This work opens the doors for more investigations of the multifunctional properties of these novel types of lattices and their engineering applications. Furthermore, the generated comprehensive data are useful in optimizing latticed structures using topology optimization techniques. [ABSTRACT FROM AUTHOR]

Thin-Walled Tubes (TWT) are widely used as crashworthiness elements to absorb and dissipate kinetic energy during collision through plastic deformation. Various design strategies, including nested tubes, triggers, and filling with lattices, are commonly used to enhance the crashworthiness of TWT. Additive Manufacturing (AM) offers unique opportunities to produce complex lattice-filled TWT with higher precision, but challenges persist in the design and fabrication of bi-tubular TWT to enhance crashworthiness. The aim of this study is to propose an approach for hybrid lattice filling in bi-tubular structures. In the preliminary phase, the parametric study was conducted to understand the influence of tube cross-section geometry, thickness, and trigger hole diameter on the crashworthiness of empty TWT using Taguchi's L9 orthogonal array. Empty TWTs were fabricated using Selective Laser Sintering (SLS) with PA12 material and compressed uni-axially at 8 mm/min speed. In the second phase, bi-tubular TWT was filled with three different unit cells such as Cube, Kelvin, and Octet Truss (OT) having 30% relative density. In the lattice filling approach, two different strategies were followed such as uniform and hybrid lattice filling. Designed TWTs were fabricated and tested under uni-axial compression at two different speeds such as 8 mm/min and 8 mm/sec. Based on the results of the preliminary study, it has been observed that cross-section geometry and tube thickness significantly enhance SEA through an increase in the stiffness and number of folding. With the help of the Signal to Noise (S/N) ratio graph, appropriate levels were selected as input for the hybrid lattice-filling approach. The results of the second phase revealed that hybrid lattice filling significantly enhances the deformation modes, energy absorption, and crashworthiness properties of TWTs. Hybrid lattice-filled TWT offers better Specific Energy Absorption (SEA) as 18.32 kJ/kg at 8 mm/sec compression speed, which is 113.9% higher than empty and 42.8% higher than uniform lattice-filled TWT. This work demonstrated that adopting the hybrid lattice-filling approach is one of the potential ways to enhance the crashworthiness of protective equipment such as crash boxes and frames. [ABSTRACT FROM AUTHOR]

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Selective laser sintering (SLS) is a powder bed fusion technology employing polymeric powder as a potential feedstock. It results in the 3D printing of parts layer by layer through the partial melting of powder particles followed by their fusion. Laser is an indispensable part of the SLS system and acts as a heat source and delivers the required energy to the powder bed to achieve sintering. Thus, this study aimed to understand the implications of the laser power ratio (LPR) on the sinterability and quality of sintered printlets. Physical mixtures (PMs) of Kollicoat® IR and novel IR-absorbing dye (1.25% w/w) were subjected to sintering using SLS 3D printer. Resultant 3D printlets were thoroughly investigated regarding physico-technological aspects, including printing yield, dimensional accuracy, average sintered layer thickness, weight variation, breaking force, friability, disintegration time, and dye content. The findings of this physical depiction were used to assess the impact of LPRs on the quality of 3D printlets, leading to the selection of an optimized batch, which was further corroborated using solid state, topographical, and microtomographical investigations. LPR had implications on printing accuracy, densification, and consolidation of printlets, imparting mechanical strength to printlets. It was found that the highest LPR (3.0) assisted in prototyping the printlets with relatively highest dimensional accuracy and mechanical properties due to the optimum energy transfer to the powder bed. Key findings of this study confirmed the feasibility of achieving versatility in SLS-mediated fabrications by varying LPRs to achieve desired personalization and customizations. [ABSTRACT FROM AUTHOR]

The aim of this work is to investigate the sound absorption properties of open-porous polyamide 12 (PA12) structures produced using Selective Laser Sintering (SLS) technology. The examined 3D-printed samples, fabricated with hexagonal prism lattice structures, featured varying thicknesses, cell sizes, and orientations. Additionally, some samples were produced with an outer shell to evaluate its impact on sound absorption. Experiments were conducted using the transfer function method with an acoustic impedance tube in the frequency range of 250 Hz and 6400 Hz. The results showed that the studied geometric factors significantly affected the sound absorption of the PA12 samples. In some cases, the hexagonal prism lattice structures demonstrated relatively high sound absorption properties. Thanks to their properties such as lower weight, recyclability, and resistance to moisture and chemicals, these structures become competitive with commonly used sound-insulating materials, making them promising candidates for sound absorption. Furthermore, numerical simulations using Ansys software confirmed that the sound absorption properties of the open-porous material structures generally increased with higher specific airflow resistance. The findings highlight the advantages of 3D printing technology in producing complex, highly customizable porous structures for noise reduction applications. [ABSTRACT FROM AUTHOR]

ABSTRACT Background Methods Results Conclusions High tibial osteotomy (HTO) is a surgical procedure for treating certain knee conditions. Proper execution of HTO can preserve joint function and delay or avoid the need for total knee replacement. This study compared different 3D printing techniques (fused deposition modeling, selective laser sintering, and direct metal laser sintering) and a navigation system for their suitability in assisting HTO surgeries.Tibial saw‐bones were used as models, and surgical guides and the navigation system were employed during the procedures. Six parameters (planning time, manufacturing time, delivery time, material cost, operation time, and accuracy) were evaluated. One‐way analysis of variance (ANOVA) and t‐test were used for the analysis.The results showed that the metal surgical guides had the highest accuracy (angle differences mean, 2.4°) and operation time (mean 9.75 min), followed by plastic guides, classic guides, and the navigation system. The differences in accuracy were attributed to factors like rigidity, melting point, and errors during incisions.The study recommended metal surgical guides as the best option for assisting HTO due to their accuracy and operation time. And the results have implications for orthopedic surgeons performing HTO surgeries, as they can use this information to improve postoperative outcomes, such as mechanical axis alignment and quality of life for HTO patients. [ABSTRACT FROM AUTHOR]

The paper highlights the realization of 3D-printed parts with complex geometries, such as chess-like pieces, using polyamide 12 (PA12) as polymeric powder via selective laser sintering (SLS). The research activity focuses on the study of the powder printability, the optimization of the printing parameters, and the tomographic evaluation of the printed objects. Morphological analyses were carried out to study the PA12 powder microstructure considering that SLS required specific particle size distribution and shape, able to guarantee a good flowability necessary to take part in a sintering process. DSC and TG analyses were performed to determine the sintering window and the crystallinity degree, and to evaluate the thermal stability of the PA12 powder due to the importance of the powder processability for the SLS process. The novelty lies in the realization of chess-like pieces very challenging to print via SLS due to their different and highly detailed structures, and the in-depth analysis of the dimensional accuracy evaluated by micro-tomography. The 3D-printed samples obtained show high printing quality and dimensional stability. The μ-CT analysis also confirms the key role of the object shape and section changes on the final porosity of the chess-like pieces. [ABSTRACT FROM AUTHOR]

This review paper delves into the manufacturing methods, material properties, and applications of polymer‐based composites in the field of advanced manufacturing, offering a detailed explanation of their production through various additive manufacturing (AM) techniques and their diverse applications across multiple industries. Polymer‐based composite materials have emerged as crucial elements in AM due to their enhanced properties and design versatility, enabling the creation of components with unprecedented performance characteristics. The paper comprehensively covers the major AM methods employed for composite materials, including fused filament fabrication, Digital Light Processing/Stereolithography, Direct Ink Writing, and Selective Laser Sintering. Each of these methods is explored in terms of its mechanism, suitability for different composite materials, and the resulting material properties. The review also provides an insightful analysis of how these AM techniques are revolutionizing industries such as soft robotics, mechanical, electrical, and biomedical fields. The paper concludes by discussing the current challenges in this domain and projecting future trends in the development and application of composite materials in advanced manufacturing. This review aims to offer a comprehensive resource for researchers and practitioners in the field, highlighting the transformative impact of polymer‐based composites in AM and their growing significance across various sectors. Highlights: Comprehensive review and classification of novelties in printing method for polymer based composite material manufacturing.Introduces innovative techniques to create and enhance material properties of composites.Explores interdisciplinary applications in biomedical, electronics, and sensors, demonstrating material versatility.Provides a systematic correlation between manufacturing method, material properties, and applications of novel polymer‐based composites. [ABSTRACT FROM AUTHOR]

Highlights A route for the synthesis and additive manufacturing of a polymer‐silica nanocomposite with polyamide 12 (PA12) polymer as the matrix material and silica nanoparticles as the reinforcing filler, has been presented in this work to enable the reusability of PA12 powder waste. PA12 powder formerly has been used in selective laser sintering to manufacture customized implants and lightweight structural components in the medical, automotive, and aerospace industries. Nano‐sized silica particles with varying dispersibility have been used as a filler with different weight contents (1% and 3%) in PA12 composites. These nanoparticles were coated with polyvinyl alcohol to achieve uniform dispersion. The nanocomposite filaments have been extruded and the final manufactured part has been printed by fused filament fabrication. SEM, EDX, and PSD showed that nanoparticles were homogeneously distributed, and the fabricated structures were crack‐free for adapted processing parameters. DSC, FTIR, and mechanical testing at different processing stages of the material showed enhanced mechanical and thermal properties compared to waste PA12. All manufactured composite structures showed an increase in tensile modulus and tensile strengths up to 30%. This approach can be used to improve the properties of PA12 waste and its further utilization for various applications. Organic solvent—free method for the reinforcement of waste polyamide 12 material. Comprehensive insight into the dispersity of nano‐silica in polymer matrix. Increase of up to 30% tensile strength for 3 wt% nano‐silica loading. [ABSTRACT FROM AUTHOR]

Selective laser sintering (SLS) applications are rapidly growing in various sectors such as automobile, aeronautics, biomedical and custom consumer products. The properties of SLS made parts exhibit high dependence on the settings of process parameters, which can be improved by choosing and adjusting sintering conditions accurately. This paper presents research work for evaluating the effect of process parameters on the tensile properties of the part manufactured on Farsoon SS402P SLS from recycled ageing FS 3300PA which is PA-12 based powder and standard operating parameters using Response Surface Methodology (RSM) design of experiments. Typically, the recommendation from the manufacturer's laser power is 70watt. The research is designed to fabricate the parts by SLS with threepart arrangements i.e. (0-degree XY/Y, 90-degree YZ/Y and 180-degree YZ/Y) by three different value of laser power, which are 67.5watt, 70watt, and 72.5watt with different values of layer thickness i.e. (0.09mm, 0.12mm and 0.15mm). Comparison have been made between the virgin powder and recycled power regarding tensile result. Tensile tests have been performed as per the ASTM D638 standard using recommendations from ISO/ASTM 52921. According to the results, effect of laser power is successfully analyzed by employing tensile strength test. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) have drawn substantial attention on account of their outstanding properties. Additive manufacturing (AM), which has emerged as a successful approach for fabricating metallic materials, allows for the production of complex components based on three-dimensional (3D) computer-aided design (CAD) models. This paper reviews the advancements in the AM of HEAs, encompassing a variety of AM techniques, including selective laser melting (SLM), selective laser sintering (SLS), selective electron beam melting (SEBM), directed energy deposition (DED), binder jetting (BJT), direct ink writing (DIW), and additive friction stir deposition (AFSD). Additionally, the study discusses the powders and wires utilized in AM, the post-processing of AM-processed HEAs, as well as the mechanical and corrosion properties of these alloys. The unique ultra-fine and non-equilibrium microstructures achieved through AM result in superior mechanical properties of HEAs, like improved strength and ductility. However, research regarding certain aspects of HEA AM, such as fatigue properties and creep deformation behavior, is still relatively scarce. Future research should focus on overcoming the existing limitations and exploring the potential of HEAs in various applications. [ABSTRACT FROM AUTHOR]

Ti-6Al-4Nb-4Zr (mass%) was prepared by selective laser melting (SLM) under various conditions, and the microstructure evolution resulting from SLM processing and subsequent heat treatments was investigated. The effects of the unique SLM-induced microstructure on the high-temperature compressive strength and creep properties of the samples were then elucidated. Under rapid cooling conditions, the martensitic structure formed in a scale--like pattern, with a 100µm in size, consistent with the laser scanning pattern. By contrast, under slow cooling conditions, the α/β lamellar structure formed in β grains with a 300µm grain size instead of in a scale-like pattern. The martensitic structure drastically changed to a Widmanstätten structure during heat treatment. The equiaxed α phase also formed at the interface of the scale-like patterns. By contrast, the α/β lamellar structure did not exhibit a change in response to heat treatment. The compressive strength of the SLM samples was governed by the martensite α size and the grain size, both of which depended on the cooling rate. The dominant creep deformation mechanism at 600°C and under a loading stress of 137 MPa was grain boundary sliding. The creep life depended on the grain size. The HIP treatment improved the creep life because it eliminated pores introduced by the SLM process. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) enables fabricating intricate objects with complex geometries previously unattainable through conventional methods. This process encompasses various techniques, including powder bed fusion (PBF), such as selective laser sintering (SLS) and multi-jet fusion (MJF). These techniques involve selectively melting powdered polymer material, predominantly utilizing engineering thermoplastics layer by layer to create solid components. Although their mechanical properties have been extensively characterised, very few works have addressed the influence of additive manufacturing on fracture behaviour. In this context, we present our work demonstrating the presence of anisotropy in fracture behaviour due to the build orientation as well as the PBF methods. To evaluate this anisotropy, the fracture behaviour of polyamide 12 polymer manufactured by SLS and MJF were investigated with experiments and numerical modelling of Mode I compact tension (CT) specimens. Experiments were monitored by digital image correlation (DIC) and infra-red thermography (IRT). Additionally, the fractured surfaces are analysed using scanning electron microscopy. Comparative analyses between SLS and MJF technologies unveiled dissimilar trends in mechanical strength, build-orientation effects, and fracture properties. [ABSTRACT FROM AUTHOR]

The additive manufacturing technique performed via laser powder bed fusion has matured as a technology for manufacturing cemented carbide parts. The parts are built by additive consolidation of thin layers of a WC and Co mixture using a laser, depending on the power and scanning speed, making it possible to create small, complex parts with different geometries. NbC-based cermets, as the main phase, can replace WC-based cemented carbides for some applications. Issues related to the high costs and dependence on imports have made WC and Co powders emerge as critical raw materials. Furthermore, avoiding manufacturing workers' health problems and occupational diseases is a positive advantage of replacing WC with NbC and alternative binder phases. This work used WC and NbC as the main carbides and three binders: 100% Ni, 100% Co, and 50Ni/50Co wt.%. For the flowability and spreadability of the powders of WC- and NbC-based alloy mixtures in the powder bed with high cohesiveness, it was necessary to build a vibrating container with a pneumatic turbine ranging from 460 to 520 Hz. Concurrently, compaction was promoted by a compacting system. The thin deposition layers of the mixtures were applied uniformly and were well distributed in the powder bed to minimize the defects and cracks during the direct sintering of the samples. The parameters of the L-PBF process varied, with laser scanning speeds from 25 to 125 mm.s─1 and laser power from 50 to 125 W. Microstructural aspects and the properties obtained are presented and discussed, seeking to establish the relationships between the L-PBF process variables and compare them with the liquid phase sintering technique. [ABSTRACT FROM AUTHOR]

Background: The fit accuracy of removable partial dentures (RPDs) is essential for the functionality, patient comfort, and durability of RPDs. Traditional fabrication methods, like lost-wax casting, are reliable, but labor intensive, potentially affecting the fit accuracy of RPDs. Advances in digital fabrication techniques offer new avenues to improve RPD precision. This systematic review and meta-analysis will assess the impact of digital fabrication methods on the fit accuracy of RPDs compared to conventional techniques. Objective: To evaluate whether digital fabrication methods, specifically CAD/CAM and additive manufacturing, offer superior fit accuracy for RPD frameworks over conventional methods. Methods: The study protocol was registered with PROSPERO (registration number CRD42024586891). A comprehensive literature search was conducted across PubMed, the Cochrane Library, Scopus, and Ovid MEDLINE databases, covering publications published up to July 2024. The inclusion criteria comprised in vitro studies comparing the fit accuracy of digital versus conventional RPD fabrication techniques, with quantitative outcomes, such as the mean gap size or seating accuracy. The data were extracted and synthesized using a random-effects meta-analysis model. Results: Eleven studies met the inclusion criteria, with seven studies included in the meta-analysis. The mean gap size for digitally fabricated RPDs was 140 µm, compared to 164 µm for conventional methods, with a weighted mean difference (WMD) of 26.29 µm, favoring digital techniques. The subgroup analysis indicated variability in the fit across different digital techniques, with milling showing the best results, although the differences were not statistically significant. Limitations: The analysis included only in vitro studies, limiting the clinical generalizability of the findings. Additionally, heterogeneity in the study design and measurement methods persisted, which could have impacted the overall conclusions. Conclusions: Digital fabrication methods demonstrated a trend toward improved fit accuracy in comparison to conventional techniques, although the differences were modest. Future research should focus on standardizing digital workflows and conducting clinical trials to confirm these findings. [ABSTRACT FROM AUTHOR]

In biomedical applications, various additive manufacturing (AM) techniques such as fused deposition modeling (FDM), inkjet, stereolithography (STL), direct powder extrusion (DPE), and selective laser sintering (SLS), as well as other digitally controlled 3D printing (3DP) techniques, are used. Advances in AM methods have led to the development of tissues, microdevices, artificial organs, personalized prostheses and orthoses, dental and various bone implants, biopharmaceutical applications and drug delivery system (DDS), and patient-specific surgical models, etc. that require multiscale structures, materials and functions. It enables the three-dimensional (3D) design and manufacturing of biomedical products with complex geometries. Additionally, it enables the modeling and 3DP using the biomimetic approach for applications that require lightweight and durable structures as well as biocompatibility. The purpose of this study is to review macro-to-nano multiscale AM technologies, design and modeling status, materials, and applications used for biomedical applications. Additionally, recommendations are given on what needs to be done to overcome the current limitations and challenges of micro/-nano printing in current AM technologies. [ABSTRACT FROM AUTHOR]

Additive Manufacturing (AM) has emerged as an important digital technology in improving production efficiency by analysing possible environmental impacts of the operations. Therefore, this study aims to investigate the impacts of redesigned products for transition to AM on sustainable production processes. In this study, an industrial-scale product was redesigned according to AM principles and manufactured using the Fused Deposition Modelling (FDM) technique. The environmental impacts of the production methods were evaluated in terms of material consumption and carbon dioxide (CO2) emissions using the Life Cycle Assessment (LCA) method. Thus, according to LCA results, the use of a single type of material and production method for the redesigned product, as well as reducing the amount of material used by eliminating the fasteners, resulted in a 60.45% reduction in material consumption and 85.59% reduction in CO2 emissions compared to CM. Although the production time in CM is shorter than FDM, the necessity of a mould design and manufacture by pre-processing resulted in an increase in delivery time. Results show that the material unit costs for both manufacturing methods are very similar. This study provides various implications that create sustainable development in the manufacturing industry for the transition to AM. ABBREVIATIONS: AM, Additive Manufacturing; CAD, Computer-Aided Design; CAE, Computed-Aided Engineering; CM, Conventional Manufacturing; CNC, Computer Numerical Control; CO2, Carbon Dioxide; DFAM, Design for Additive Manufacturing; DIY, Do It Yourself; FDM, Fused Deposition Modelling; LCA, Life Cycle Assessment; LEM, Laser Engraving Machine; PLA, Polylactic Acid; SLA – Stereolithography; SLS, Selective Laser Sintering; 3D – Three Dimensional [ABSTRACT FROM AUTHOR]

Introduction: The electro-actuated shape memory polymer scaffold has gained increasing attentions on the utilization of minimally invasive surgery for bone defect repair, which requires to construct an efficient conductive network to accomplish electrical-to-thermal conversion from conductive fillers to the entire matrix evenly. Objectives: In this study, multiwall carbon nanotube (MWCNT) was convective self-assembled on the ZnO tetrapod (t-ZnO) template, where MWCNT was controlled to disperse uniformly and regulated to contact with each other effectively due to the immersion capillary force during the evaporation loss of the convective self-assembly process, leading to an interwoven layer on the t-ZnO surface. Methods: The prepared t-ZnO@MWCNT assembly was embedded in the poly(L-lactic acid)/thermoplastic polyurethane (PLLA/TPU) scaffold fabricated via selective laser sintering to construct a 3D conductive MWCNT network for improving the electro-actuated shape memory properties. Results: It was observed that the interconnected MWCNT formed a 3D conductive network in the matrix without significant aggregation, which boosted the electrical-to-thermal properties of the scaffold, and the scaffold containing t-ZnO@MWCNT assembly possessed better electro-actuated shape memory properties with shape fixity of 98.0% and shape recovery of 98.8%. Conclusion: The scaffold exhibited improved electro-actuated shape memory properties and mechanical properties and the osteogenic inductivity was promoted with the combined effect of t-ZnO and electrical stimulation.

Depending on the 3D-printing orientation, the anisotropy of the elastic characteristics of the Inconel 625 alloy generated with selective laser sintering from powders is investigated. The impact of the original powder combination and the following heat treatment (post-printing treatment) on the anisotropy of the alloy elastic characteristics is assessed. As demonstrated, the suggested treatments can lessen the anisotropy of the alloy elastic characteristics. Based on knowledge of the elastic constants of the single crystal and x-ray texture features, the results of a theoretical estimation of the elastic and shear moduli, Poisson’s ratio, and their anisotropy in the horizontal and vertical directions of 3D printing are provided. As demonstrated, the obtained theoretical values differ by 6–10% from the corresponding experimental values. The calculated stress–strain state can be more accurately calculated with the use of the estimated elastic characteristics and their anisotropy. The strategy for 3D-printing complicated components from Inconel 625 alloy may be made more effective.

The research objects are gas turbine engines parts, manufactured using an innovative method of additive manufacturing – selective laser sintering. The main problem solved in this work is the low quality of the surface layer and the residual porosity of the parts obtained by this method, which significantly limits their operational characteristics and durability. As a result of the experimental studies, rational operating parameters of diamond smoothing were established. This allowed to significantly improve the surface quality and increase the operational characteristics of parts made of heat-resistant alloys INCONEL 718 and an intermetallic alloy based on titanium aluminide OX45-3ODS. The effectiveness of diamond smoothing is explained by local plastic deformation and compaction of the surface layer of parts under the influence of high contact pressures and temperatures. This leads to a significant reduction in surface roughness, an increase in the surface hardness due to strain hardening and a significant reduction in the size and number of residual pores. A characteristic feature of the obtained results is the ability to control the quality parameters of the surface layer by varying the diamond smoothing operating parameters – smoothing force, feed, radius, and geometry of the smoother's working part. The established regularities of the smoothing operating parameters have an impact on the quality characteristics of the surface. This information can be utilized in the development of highly efficient technological processes for the production and restoration of gas turbine engines, critical components of unmanned aerial vehicles, obtained through selective laser sintering. Implementing the elaborated technological recommendations will permit broadening the range of goods produced by additive manufacturing and enhancing their capacity and dependability during operation under conditions of cyclical loads and extreme temperatures.

Polyesters have garnered significant attention in bone tissue engineering (BTE) due to their tunable degradation rates, biocompatibility, and convenient processing. This review focuses on recent advancements and challenges in the 3D printing of polyester‐based scaffolds for BTE. Various 3D printing techniques, such as fused deposition modeling (FDM), selective laser sintering (SLS), vat photopolymerization (VP), and Wet‐spun additive manufacturing, are explored, emphasizing their ability to construct scaffolds with precise architectural control. The main challenges in 3D printed polyester scaffolds are their limited mechanical properties, lack of inherent bioactivity, and the release of acidic byproducts during biodegradation. Strategies to enhance scaffold performance, such as incorporating bioactive ceramics and growth factors, are discussed, focusing on improving osteoconductivity, osteoinductivity, and mechanical strength. Recent studies on integrating these components into polyester scaffolds and techniques to optimize scaffold porosity and biodegradability are presented. Finally, the review addresses ongoing issues, such as the difficulty of incorporating some biomolecules and bioceramics during 3D printing and improved clinical translation. This comprehensive overview aims to provide insight into the future directions and potential solutions for overcoming the limitations of 3D‐printed polyester‐based scaffolds in BTE. [ABSTRACT FROM AUTHOR]

Background: The purpose of this study was to evaluate the efficacy of selective laser sintering (SLS) against the traditional casting method in fabricating customized Co-Cr dental posts, employing 3D coordinate metrology for analysis. Methods: A 10 mm post space was prepared in a transparent acrylic block using a red ParaPost XP drill (1.25 mm diameter). An impression of this cavity was taken with a 1.143 mm diameter ParaPost impression post and auto-polymerizing acrylic resin. The resin patterns obtained were digitized with a Straumann Cares scanner, generating STL files, which were forwarded to Renishaw for the production of 10 Co-Cr posts through SLS. Simultaneously, the original resin patterns underwent investment and casting in Co-Cr alloy. The dimensional accuracy of the posts produced by both methods was evaluated using the triple scan method. Results: The mean discrepancy was − 0.048 mm when comparing the dimensions of scanned resin posts to those of the conventionally cast posts, and − 0.067 mm between the scanned SLS-produced posts and the original resin patterns. Statistical analysis indicated no significant difference between the two sets of mean values (P = 0.107). Conclusion: SLS technology is a viable alternative to the conventional casting technique for the manufacture of customized Co-Cr posts. Furthermore, SLS offers advantages in terms of cost and time efficiency without compromising the accuracy of the end product. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the influence of pre-heating characteristics on the mechanical properties and forming process of selective laser sintering (SLS) printed PES-HmA samples. An experimental setup with four heating tubes was designed to study the pre-heating temperature distribution on the powder bed. The pre-heating temperature distribution on the powder bed was captured using a thermal imaging camera. A method for evaluating pre-heating temperature distribution based on the average and standard deviation of surface temperature was proposed. The heating tube installation position was optimized using a response surface experiment study based on the temperature distribution evaluation. By optimizing the installation position of the tubes, the temperature distribution on the powder bed tends to become uniform. The effect of pre-heating temperature value and distribution on the mechanical properties of the SLS printed PES-HmA samples was also experimentally investigated. The cross sectional microstructure of the printed samples were examined by scanning electron microscope to analyze the layer formation process at different pre-heating temperature. By increasing the pre-heating temperature from 70°C to 100°C, the material diffusion at the layers interface was improved, which made the tensile strength of sample increased by 376%, and the flexural strength increased by 224%. [ABSTRACT FROM AUTHOR]

The article discusses the evolution of 3D printing in the pumps industry, highlighting its role in creating custom molds, rapid prototyping, and intricate components. Additive manufacturing offers advantages such as faster production times, higher accuracy, and the ability to create complex shapes without additional tooling. While 3D printing is not a one-size-fits-all solution and comes with challenges like upfront costs and limitations for larger parts, it is increasingly becoming a standard part of production lines in the pump sector, with opportunities for further refinement and innovation in the future. [Extracted from the article]

Materials and structures with tunable mechanical properties are essential for numerous applications. However, constructing such structures poses a great challenge since it is normally very complicated to change the properties of a material after its fabrication, particularly in pure force fields. Herein, we propose a multistep and elastically stable 3D mechanical metamaterial having simultaneously tunable effective Young's modulus and auxeticity controlled by the applied compressive strain. Metamaterial samples are fabricated by 3D printing at the centimetric scale, with selective laser sintering, and at the micrometric scale, with two-photon lithography. Experimental results indicate an elementary auxeticity for small compressive strains but superior auxeticity for large strains. Significantly, the effective Young's modulus follows a parallel trend, becoming larger with increasing compressive strain. A theoretical model explains the variations of the elastic constants of the proposed metamaterials as a function of geometry parameters and provides a basic explanation for the appearance of the multistep behavior. Furthermore, simulation results demonstrate that the proposed metamaterial has the potential for designing metamaterials exhibiting tunable phononic band gaps. The design of reusable elastically stable multistep metamaterials, with tunable mechanical performances supporting large compression, is made possible thanks to their delocalized deformation mode. [ABSTRACT FROM AUTHOR]