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In this study, continuous carbon reinforced C f /(Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C–SiC high entropy ceramic matrix composites were additively manufactured through paper laminating (PL), direct slurry writing (DSW), and precursor infiltration and pyrolysis (PIP). (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C high entropy ceramic (HEC) powders were synthesized by pressureless sintering and ball milling. A certain proportion of HEC powder, SiC powder, water, binder, and dispersant were mixed to prepare the HEC-SiC slurry. Meanwhile, BN coating was prepared on the 2D fiber cloth surface by the boric acid-urea method and then the cloth was cut into required shape. Additive manufacturing were conducted subsequently. Firstly, one piece of the as-treated carbon fiber cloth was auto-placed on the workbench by paper laminating (PL). Then, the HEC-SiC slurry was extruded onto the surface of the cloth by direct slurry writing (DSW). PL and DSW process were repeated, and a C f /HEC-SiC preform was obtained after 3 cycles. At last, the preform was densified by precursor infiltration and pyrolysis (PIP) and the final C f /HEC-SiC composite was prepared. The open porosity of the C f /HEC-SiC composites, with the HEC volume fractions of 15, 30 and 45%, were 7.7, 10.6, and 11.3%, respectively. And the density of the C f /HEC-SiC composites, with the HEC volume fractions of 15, 30 and 45%, were 2.9, 2.7 and 2.3 g/cm3, respectively. The mechanical properties of the C f /HEC-SiC composites increased firstly and then decreased with the HEC content increase, reaching the maximum value when the HEC volume fraction was 30%. The mechanical properties of the C f /HEC-SiC composites containing 45, 30 and 15% HEC were as follows: flexural strength (180.4 ± 14 MPa, 183.7 ± 4 MPa, and 173.9 ± 4 MPa), fracture toughness (11.9 ± 0.17 MPa m1/2, 14.6 ± 2.89 MPa m1/2, and 11.3 ± 1.88 MPa m1/2), and tensile strength (71.5 ± 4.9 MPa, 98.4 ± 12.2 MPa, and 73.4 ± 8.5 MPa). From this study, the additive manufacturing of continuous carbon fiber reinforced high entropy ceramic matrix composites was achieved, opening a new insight into the manufacturing of ceramic matrix composites. [ABSTRACT FROM AUTHOR]

Abstract Al 2 O 3 /Cu-O composites were fabricated from the paper-derived alumina matrix infiltrated with a Cu-3.2 wt% O alloy. Paper-derived alumina preforms with an open porosity ranging from ∼ 14 to ∼ 25 vol% were prepared by sintering of alumina-loaded preceramic papers at 1600 °C for 4 h. Pressureless infiltration at 1320 °C for 4 h of the preforms with Cu–O alloy resulted in the nearly dense materials with good mechanical and electrical properties, e.g. fracture toughness up to 6 MPa m0.5, four-point-bending strength up to 342 MPa, Young's modulus up to 281 GPa and electrical conductivity up to 2 MS/m depending on the volume fraction of copper alloy in the composites. The technological capability of this approach was demonstrated using prototypes in various engineering fields fabricated by lamination, corrugating and Laminated Object Manufacturing (LOM) methods. [ABSTRACT FROM AUTHOR]

In this study, additive-manufactured silicon carbide preforms were joined and densified by reaction bonding via liquid silicon infiltration. The silicon carbide preforms were first printed by binder jetting additive manufacturing. To demonstrate concurrent joining and densification, two preforms with carbon or parchment papers at the interface were concurrently joined and infiltrated by liquid silicon. Results showed a robust interface with thicknesses ranging from 150 to 500 µm, depending on the paper type and the number of paper layers. High-energy synchrotron X-ray revealed that β-phase silicon carbide was formed inside the interface. Finally, two additively manufactured samples with complicated channel geometry were successfully joined. Energy dispersive spectroscopy of the interface of the channeled samples showed a consistent and robust joining. This concurrent approach of joining and densification enables efficiency improvement of fabricating silicon carbide parts with complicated geometries and widens geometry freedom for additive manufacturing of silicon carbide. [ABSTRACT FROM AUTHOR]

[Display omitted] • An approach to colorimetric detection of corrosion inhibitors using a portable sensor; • The detection was performed using an Arduino microcontroller photoelectric sensor. • The sensor was able to detect color intensities in the function of the RGB channels; • The colorimetric protocol was based on a reaction of the TBPE and QAs; • As a proof of concept an analysis of a Corton corrosion inhibitor was performed. In this work, we report a complete and portable analytical instrumentation dedicated to the colorimetric analysis of corrosion inhibitors. The construction of the analytical tool was planned based on carousel architecture and it involves a simple combination of a 3D-printed holder containing eight circular zones and an Arduino microcontroller photoelectric sensor. In addition, paper-based analytical devices (PAD) were manufactured in the form of microzones using manual cutting and assembled in the 3D printed holder for performing colorimetric measurements of quaternary amines in wastewater samples from the petroleum industry. A blue dye was used as a model color and the obtained pixels responses through the proposed analytical tool and well-known smartphone-based analysis revealed similar colorimetric intensities, thus clearly demonstrating the high performance of the 3D-printed analytical instrumentation. The target colorimetric reaction occurs via the interaction of ammonium quaternary present in corrosion inhibitors composition with the chromogen 3′, 3″, 5′, 5″ – tetrabromophenolphthalein-ethyl-ester (TBPE) in an acidic medium. Detailed optimization of the colorimetric reaction involving the ammonium quaternary was successfully performed, as well as the evaluation of possible physical–chemical interferences (pH, carbonate levels, and temperature) mostly usual in produced water from petroleum pipelines. Recovery studies of ammonium quaternary in real produced water samples exhibited acceptable performance (88 to 121%). Thus, the obtained results successfully demonstrated that the proposed 3D-printed analytical system associated with PADs offers a huge potential to be used for colorimetric detection of corrosion inhibitors in wastewater samples and it can be used in the point-of-need involving the petroleum industry field. [ABSTRACT FROM AUTHOR]

[Display omitted] • Use of napkin paper for production of low-cost analytical devices is reported. • New stamping method for creation of paraffin hydrophobic barriers is described. • Novel method for colorimetric quantification of ethanol in beverages is presented. • Analytical application for analysis of real samples is successfully demonstrated. • Results showed great concordance when compared to UV–vis spectrophotometry. In this work we report for the first time the use of napkin paper as substrate for production of paper analytical devices (PADs). Napkin paper is a more accessible and cheaper option compared to the most commonly used chromatographic and filter papers. The PADs were easily fabricated by depositing hydrophobic paraffin barriers using a simple stamping contact method. The stamps used here were fabricated by 3D printing. To the best of our knowledge, this is the first report of this stamping approach aiming production of paraffin barriers in PADs. The PADs proposed here were utilized for colorimetric determination of alcohol content in beverages. This method was based on the redox reaction between ethanol and dichromate in acidic medium. As far as we know, this is the first PAD-based method exploring this principle. The image-based method showed a linear range between 0 and 50 % (v/v) ethanol, with a limit of detection of 1.5 %. This concentration range allows the analysis of various alcoholic beverages. The results obtained during the analysis of real samples presented great concordance with the values found by UV–vis spectrophotometry, used for validation (relative error < 5 %). Thus, the new PAD-based colorimetric method reported here shows great potential for applications in areas such as food control and forensics. Moreover, the use of napkin paper for fabrication of PADs appears to be a promising, easier and less expensive option, being specially interesting for places with limited resources. [ABSTRACT FROM AUTHOR]

[Display omitted] • First coupling of BIA systems to electrochemical paper analytical devices (ePADs). • To adapt the ePAD, a new semi-transparent BIA cell was developed using 3D-printing. • This platform was used for amperometric detection of 5-hydroxytryptophan (5-HTP). • First BIA-based method for 5-HTP analysis. • Real samples were analyzed and the results validated with UV–vis spectrophotometry. This work reports, for the first time, the association of electrochemical paper analytical devices (ePADs) with batch injection analysis (BIA) systems. The novel 3D-printed BIA cell utilized here is semi-transparent (3D-printed by SLA/DLP technology), while the three-electrode paper device was fabricated by pencil drawing. This ePAD/3D-BIA platform was employed for the amperometric detection of 5-hydroxytryptophan (5-HTP). To the best of our knowledge, this is the first BIA method for determining this analyte. The parameters of the method were studied and optimized. The ePAD/3D-BIA system presented good repeatability and reproducibility, with relative standard deviations (RSDs) < 5%, besides high analytical frequency (180 injections per hour). In addition, the ePAD showed excellent performance and lifetime, being able to be utilized for up to eight consecutive days. Under the best conditions, amperometric response of 5-HTP provided linearity in the range of 0.165 to 150 µmol L−1, with a limit of detection (LOD) of 50 nmol L−1. As a proof of principle, the ePAD/3D-BIA was used to analyze 5-HTP in commercial food/pharmaceutical samples. The results presented great precision (RSD ≤ 1.5%) and agreement with the values obtained by UV–vis spectrophotometry (95% confidence level). These findings show the potential of the novel system proposed here. The ePAD/3D-BIA proved to be an efficient, fast and reliable platform that can be a useful tool for the analysis of electroactive species. Moreover, the very low cost, practicality and simplicity may offer interesting advantages over conventional BIA systems. [ABSTRACT FROM AUTHOR]

Paper-based electronics with carbon nanomaterials incorporated have several advantages including recyclability, biodegradability, non-toxicity, low cost and ease of fabrication and disposal. Herein, carbon nanoparticles (CNPs) were fabricated by Pulsed Laser Ablation in Liquid (PLAL) using three different liquid mediums, i.e. deionised (DI) water, ethanol and a magnesium-based solution. The as-fabricated nanocolloids were used as conductive inks and deposited on paper substrates. The resulting nanoparticle (NP) coatings were subjected to electrical resistivity tests via 4-point probe. Ultraviolet–Visible spectroscopy (UV–Vis) studies were conducted to determine the presence of nanomaterials. All nanocolloids produced within DI water had three distinct UV–Vis absorbance peaks at 200, 216 and 225 nm while nanocolloids produced in ethanol exhibited more peaks and significantly higher absorbance values in the range from 210 nm to 300 nm. Dynamic Light Scattering and field emission scanning electron microscopy (FESEM) were used to analyse samples for particle size and morphology respectively. The liquid medium in which PLAL was conducted was found to significantly affect the NP mean size, conductivity and surface chemistry of the resulting NPs. DI water produced smaller nanoparticles (NPs) (10–82 nm) than ethanol (60–143 nm) and magnesium-based solution (263–1389 nm) within the process parameters studied herein. The laser scan speed and fluence have a combined effect on the NP mean diameter. The surface chemistry of the NPs produced in the magnesium-based solution was analysed via X-ray photoelectron spectroscopy and it was found that the Mg, Li and Si atoms are adsorbed by the carbon NPs leading to higher conductivity of the coated paper substrates. [Display omitted] • This paper studies the effect of liquid medium on nanoparticle mean size during Pulsed Laser Ablation in Liquid (PLAL). • A complex liquid medium (magnesium-based solution) is used for the first time during PLAL of carbon targets. • The effect of laser scan speed and fluence on the nanoparticle size and conductivity is investigated. [ABSTRACT FROM AUTHOR]

We present a general methodology to evaluate the mass moments of two-dimensional domains and axisymmetric solids made of functionally graded materials. The approach developed in the paper is based on the sequence of two steps. First, the original domain integrals are converted to integrals extended to the relevant boundary by exploiting Gauss theorem. Second, for domains having a polygonal or circular shape, the boundary integrals are evaluated analytically by providing algebraic expressions that depend upon the parameters defining the density distribution, the position vectors of the vertices of the polygonal domain or the initial and ending points of an arbitrary circular sector, respectively. While the first step refers to moments of arbitrary order, the second step is limited to the most useful quantities for engineering applications, i.e. generalised mass, static moment and inertia tensor. The formulas derived in the paper are validated by means of examples retrieved from the specialised literature for which analytical results are available or have been specifically derived by the authors. Finally, in order to ascertain the computational savings entailed by the use of the proposed analytical formulas with respect to numerical techniques, the mass moments of a longitudinal section of a human femure, made of a functionally graded material and characterised by a linear density distribution, have been computed. • Mass moments for functionally graded domains expressed by boundary integrals. • Polynomial, exponential and polynomial quadratic density distributions. • General methodology for computing mass moments of order greater than 2. • Analytical evaluation of mass moments for polygonal or circular domains. • Accuracy and computational efficiency of the analytical formulas. [ABSTRACT FROM AUTHOR]

Topology optimization has seen increased interest with the rise of additive manufacturing (AM) as a fabrication method, because of its ability to exploit the geometric complexity that AM offers. However, AM still imposes some geometric restrictions on the design, most notably on minimum feature size, overhang angles, and enclosed voids. Enclosed voids are problematic because for many AM methods it is impossible to remove supports, unmelted powder or uncured liquid from them. This paper introduces a filter based on a cumulative sum flood fill algorithm to alleviate this issue in a flexible manner. This filter produces a density field where every enclosed void element is rendered solid. It successfully eliminates enclosed voids in both 2D and 3D problems, with low computational cost due to its geometric nature. In addition we demonstrate direct control over the location, amount, and size of powder removal features by varying boundary conditions for the filter, running additional flood fills, and adding morphology operators, respectively. • The cumulative sum flood fill approach is introduced in topology optimization. • The approach works as a filter and successfully eliminates enclosed voids. • Direct control can be achieved over the amount, location, and size of access channels. • Due to its geometric nature it adds little computational effort. [ABSTRACT FROM AUTHOR]

With the growing demand for green technologies, hydrogen energy devices, such as Proton Exchange Membrane (PEM) fuel cells and water electrolysers, have received accelerated developments. However, the materials and manufacturing cost of these technologies are still relatively expensive which impedes their widespread commercialization. Additive Manufacturing (AM), commonly termed 3D Printing (3DP), with its advanced capabilities, could be a potential pathway to solve the fabrication challenges of PEM parts. Herein, in this paper, the research studies on the novel AM fabrication methods of PEM components are thoroughly reviewed and analysed. The key performance properties, such as corrosion and hydrogen embrittlement resistance, of the additively manufactured materials in the PEM working environment are discussed to emphasise their reliability for the PEM systems. Additionally, the major challenges and required future developments of AM technologies to unlock their full potential for PEM fabrication are identified. This paper provides insights from the latest research developments on the significance of advanced manufacturing technologies in developing sustainable energy systems to address the global energy challenges and climate change effects. • The AM technologies relevant to PEM fabrication are reviewed. • Corrosion performance of AM materials in the PEM working environment is presented. • The challenges and prospects of AM for PEM fabrication are discussed. • AM has the potential to revolutionize the fabrication of PEM systems. [ABSTRACT FROM AUTHOR]

The significant disparity in refractive index between silicon nitride (Si 3 N 4) powder and resin poses a formidable challenge in the formulation of stable ceramic slurry with high solid content and low viscosity. This research paper systematically investigates the oxidation pretreatment of Si 3 N 4 powder and the modification process of the silane coupling agent, with a particular focus on their impacts on the rheological and curing properties of the ceramic slurry. Furthermore, the study thoroughly examines the effects of various functional group resin compounds, dispersant types, and dosages on the rheological and curing properties of the ceramic slurry. By optimizing the surface modification process of silicon nitride (Si 3 N 4) and formulating an appropriate composition for the silicon nitride (Si 3 N 4) slurry, this paper successfully prepares a Si 3 N 4 ceramic slurry with outstanding curing performance, low viscosity, and a solid content of 44 vol%. The application of photocuring molding technology enables the production of Si 3 N 4 ceramic components characterized by high precision, excellent surface quality, and intricate geometries. Moreover, this study establishes a comprehensive understanding of the relationship between the refractive index of silicon nitride ceramic slurry and essential parameters, including photocuring process variables and slurry properties. This achievement provides valuable technical guidance for the preparation and printing of silicon nitride ceramic slurry. [ABSTRACT FROM AUTHOR]

Mass production of customized parts using conventional manufacturing technologies is challenging. The increasing use of hybrid approaches is a promising way to address mass customization. Due to the widespread use of the term hybrid in manufacturing technologies, the amount of literature is increasing dramatically. Therefore, this paper aims to provide an overview of the current state of the art on the combination of additive manufacturing (AM) and metal forming. First, the term hybrid is classified, followed by examples of hybrid AM. The focus of this paper is on the combination of either sheet metal forming or bulk metal forming with either powder bed fusion or directed energy deposition. Examples of both sequences - AM before or after forming - are presented and analyzed for their potential use in hybrid parts. From the selected literature, the possibilities of this approach are derived as well as the ongoing need for future research. AM offers great potential for adjusting the microstructure and resulting material properties to improve formability. Furthermore, forming operations need to be adapted to the different material properties found in hybrid parts. [ABSTRACT FROM AUTHOR]

Directed Energy Deposition (DED), a metal additive manufacturing technique, shows promise for future orthopaedic applications, especially in bone plate manufacturing. The need for patient-specific solutions in orthopaedics is growing, driven by the limitations of traditional bone plates made from stainless steel or titanium alloys and the rising incidence of complex fractures. This paper explores the design of orthopaedic bone plates using Generative Design (GD) and Topological Optimization (TO), aimed at eventual production through DED. By focusing on design, the research addresses challenges like stress shielding, caused by the modulus disparity between conventional plate materials and natural bone. Significant findings include mass reductions of 43.7% and 44.2% for GD designs GD1 and GD2, respectively, and a 36% reduction for the TO design TO1, enhancing biomechanical performance with improved strain values. The findings demonstrate GD's effectiveness in generating anatomically congruent implants, showcasing advancements in personalized care and fracture treatment. The integration of GD and DED within the Design for Additive Manufacturing (DfAM) framework offers a promising pathway for future research focused on refining patient-specific designs and manufacturing processes, aligning with the evolving needs of orthopaedic treatments. [ABSTRACT FROM AUTHOR]

The interest in Nitinol (NiTi) as biomedical material is growing thanks to its unique properties, particularly shape memory and superelasticity. Recently, additive manufacturing (AM) has emerged as an alternative to fabricate superelastic NiTi biomedical parts. However, when using AM to fabricate NiTi parts, a proper heat treatment must follow, recommended not only to alleviate the AM-induced residual stresses, but also to develop a suitable microstructure to enhance the material superelasticity. This heat treatment is expected to modify also the NiTi corrosion behavior, which must be evaluated since corrosion may lead to the possible harmful release of nickel ions in the human environment. In this framework, the objective of the paper is to assess the mechanical and corrosion properties of a Ni-rich NiTi fabricated by laser powder bed fusion before and after heat treatment. To this aim, nano-indentation was used to evaluate superelasticity, whereas electro-chemical tests provided the corrosion potential and current density. The results of the analyses show that both the mechanical and corrosion characteristics were related to the peculiar microstructural features induced by the AM and heat treatment steps, nevertheless ageing at 600°C was the best in terms of superelasticity, while aging at 300°C assured the highest corrosion resistance. [ABSTRACT FROM AUTHOR]

This paper describes development of multi-layer deposition of Ti6Al4V added with 5 at% of Cr, 5 at% of Ni, and 2.5 at% of each Cr and Ni by μ-plasma powder arc additive manufacturing process. It presents findings on their microstructure, porosity, evolution of phases, microhardness, tensile strength, ductility, fracture morphology, fracture toughness, and abrasion resistance. Phase evolution found that α/α'-Ti and β-Ti phases are formed in all the alloys, intermetallic phase Cr 2 Ti evolved in Ti6Al4V5Cr and Ti6Al4V2.5Cr2.5Ni alloys whereas intermetallic phase Ti 2 Ni is formed in Ti6Al4V5Ni alloy. Their microstructure revealed that addition of chromium and nickel refined grains of their α-Ti and β-Ti phases. Elemental composition of the evolved phases found that at% of chromium, nickel, and vanadium in β-Ti phase is more than the α-Ti phase of the developed alloys. It enhanced their ultimate tensile and yield strength, and microhardness but reduced ductility. It changed the fracture mode from ductile to a combination of ductile and brittle mode possessing large size dimples, micropores, and cleavage facets. It is due to solid solution strengthening, evolution of intermetallic phases Cr 2 Ti and Ti 2 Ni, and grain refinement of β-Ti and α-Ti phases. Enhanced microhardness and presence of intermetallic phases improved fracture toughness and abrasion resistance of the developed alloys thus imparting them higher resistance to propagation of cracks and abrasive wear. [Display omitted] • Addition of Cr and Ni to Ti6Al4V alloy increased yield and ultimate tensile strength but reduced ductility. • The additional elements increased fracture toughness, microhardness, abrasion resistance. • The additional elements changed fracture mode to ductile and brittle with micropores and cleavage facets. • The additional elements refined grains of α-Ti and β-Ti phases. • β-Ti phase of Ti6Al4VxCryNi alloy has more at% of Cr, Ni and V than their α-Ti phase. [ABSTRACT FROM AUTHOR]

Shape Memory Alloys (SMA) are materials used to design smart structures with intrinsic functional properties and improved efficiency. This is a key aspect of aerospace industry and makes SMA good candidates in this field. One of the most widespread SMA is the equiatomic NiTi alloy which, however, has the strong limitation of poor machinability, so only simple shapes can be obtained. Additive Manufacturing processes allow to overcome this limit and to design complex shapes. Compared to other metallic materials, the optimization of the process for NiTi alloy is complicated because, beside mechanical properties and presence of defects, considerable attention needs to be dedicated to the material functionality. The high temperatures involved in the additive process significantly affect the material properties due to possible evaporation of Ni and formation of precipitates that enable a shift of the phase transformation temperatures. This paper is focused on the optimization of the process parameters of the NiTi alloy printed through the Laser Powder Bed Fusion (L-PBF) to ensure optimal pseudo-elastic behaviour, which is essential for the design of structural dampers. This was accomplished starting from simple structures and then designing a damper that couples the pseudoelasticity of NiTi with load support capacity. The L-PBF is a powder-bed technique that selectively melts layers of micrometric metal powder. A pseudoelastic NiTi powder with 50.8 at. % of Ni content was selected and characterized through scanning electron microscope (SEM) and observations connected to an Energy Dispersive X-ray Spectroscopy (EDX) probe. After that, some cubic samples were manufactured, with the dimension of 3 × 3 × 15 mm3. A set of different laser powers and scanning speeds were used to find the set of process parameters that optimize the functional properties of the printed parts. Near fully dense specimens with density higher than 99.5 % were selected for further investigations. Differential scanning calorimetry (DSC) and mechanical tests were performed on as-built and heat-treated samples. Quasi-static mechanical tests were accomplished in compression mode, at different strains, up to 8 %. It was observed that the residual strain for cyclic loading at 4 % is lower than 1 %, so good recovery of the deformation was shown. Moreover, numerical analyses that mimic the pseudoelastic behaviour in compression tests were implemented. Finally, the best set of parameters was selected on the basis of the material's ability to recover deformations and its loss factor. • Optimization of process parameters for functional behaviour of SMA. • Design of damping structure using pseudoelastic effect of Nitinol. • Internal defects observation of manufactured specimens. • Compression tests on as built and thermal treated specimens with strain up to 8 %. • Numerical simulation of compression tests with experimental correlation. [ABSTRACT FROM AUTHOR]

The main advantages of ceramic materials are their excellent thermal, chemical, and mechanical properties. They also have a much lower density than metals, making them ideal for lightweight construction, which can also be interesting for space components. However, ceramics have not been widely used due to their low ductility and the challenges of mechanical processing using conventional methods like milling and turning. Additionally, integrating different functions into a single component has been limited. The introduction of additive manufacturing (AM) technologies has revolutionized this field. It is now possible to manufacture highly complex ceramic components with unprecedented functionality. By hybridizing different manufacturing technologies and materials, additional functions such as electrical contacts, sensors, and actuators can be directly integrated, leading to improved manufacturing costs and component properties. Three different demonstrator examples are presented in this paper to give a first impression of what will be possible in the field of space applications in the future. These examples are a ceramic igniter, a ceramic reactor for thermal decomposition of H 2 O 2 , and a ceramic aerospike engine. • Additive manufacturing of ceramic components allows geometrical functionalization. • Adding of further materials to AM components allows further functionalization. • Sequential & simultaneous manufacturing available for AM of multi-material component. • Hybridization of AM technologies allows optimization of component's quality and costs. [ABSTRACT FROM AUTHOR]

The National Aeronautics and Space Administration (NASA) has been involved in the development and maturation of metal additive manufacturing (AM) for space applications since the late 2000's. Several efforts have focused on the understanding of AM processes through material characterization and testing, standards development, component fabrication, and infusion into propulsion development and flight applications. NASA matured commonly used aerospace alloys from various alloy families (Nickel, Copper, Stainless and Steel, Aluminum, and Titanium-based) through detailed AM process and heat treatment characterization, in addition to mechanical and thermophysical testing. While these alloys are actively used in many propulsion applications, there is a need for ongoing AM optimized alloys using integrated computational materials engineering (ICME) and process development for high performance applications. The applications targeted are liquid rocket engines; advanced propulsion systems; and in-space propulsion with high heat fluxes, high pressure, and/or that use propellants that can degrade alloys (e.g., hydrogen). This paper highlights the characterization and physical properties of the more common AM alloys using laser powder bed fusion (L-PBF) and laser powder directed energy deposition (LP-DED) processes. Additionally, this paper discusses some of the ongoing novel alloy development and maturation using AM for use in these harsh environments, such as GRCop-42, GRCop-84, NASA HR-1, GRX-810, and C-103. The results from these processes demonstrated that AM could enable rapid development, and that optimized alloys could be developed using ICME, yielding higher performances. These alloys have undergone modeling, fundamental metallurgical evaluations, heat treatment studies, detailed microstructure characterization, and mechanical testing campaigns. This, combined with direct application-specific component fabrication and hot-fire testing, enabled the increase of the Technology Readiness Level (TRL) through high duty-cycle testing. A background and overview of these novel AM-enabled alloys and AM processing developments including metallurgical and mechanical property studies is presented here. The latest advancement in the parallel component development and hot-fire testing and future developments for these alloys is also discussed. • Additive manufacturing (AM) has enabled development of novel alloys for extreme propulsion environments. • NASA has matured alloys including GRCop-42, GRCop-84, NASA HR-1, GRX-810, C-103. • Characterization, material properties, and hot-fire test application data has been made available. [ABSTRACT FROM AUTHOR]

Hairpin technology has recently become the predominant winding technology for the manufacturing of stators used in electric traction motors. In contrast to conventional winding techniques, the manufacturing process chain is based on rectangular wire which is bent into a three-dimensional U-shape – so-called hairpin coils. These hairpin coils have to be individually gripped and assembled to form the stator winding. There can be hundreds of hairpin coils in a single stator, which can also differ in shape. Therefore, gripping and moving the individual hairpin coils is a challenging task in terms of flexibility and cycle time. This paper presents an approach to meet the outlined requirements using additively manufactured vacuum grippers. A concept is investigated in which the vacuum is generated in a conventional vacuum ejector and fed to the vacuum gripper via hose lines. In contrast, the concept of a functionally integrated vacuum gripper manufactured by a new laser-sintering process with automated continuous fibre reinforcement is presented. Based on the laser-sintering process, a lightweight vacuum gripper with an integrated vacuum ejector can be manufactured in a single process step without additional costs for purchased parts. After a review of the state of the art in both hairpin-specific and additively manufactured lightweight grippers, experimental test series are carried out concerning the vacuum quality and the grip strength of the different vacuum gripper designs. Pull-off tests show that high holding forces of several Newtons are possible proving the basic usability of vacuum grippers for hairpins, even though the achievable vacuum quality of the functionally integrated vacuum gripper is lower than that of the conventional ejector. Comparison of the novel approaches with a conventional mechanical hairpin gripper regarding weight, production costs and production time show promising improvements. [ABSTRACT FROM AUTHOR]

In this paper, the electromagnetic wave (EMW) absorption properties of SiCN ceramics with a shellular structure prepared by 3D printing technology (DLP) at different pyrolysis temperatures were investigated. The research shows that polarization loss and multiple reflections are the principal reasons for the improvement in sample absorption performance. The shellular structure is favorable for the multiple reflections and scattering of electromagnetic wave inside the material. The turbostratic carbon, graphitic carbon and SiC generated by pyrolysis are conducive to improving the dielectric loss of the sample, adjusting its impedance matching performance and improving its absorption performance. The RL min of SiCN-1200 reaches − 21.12 dB (3.22 mm), and the effective band width is 4.20 GHz, covering the whole X-band. The excellent EMW absorption performance of DLP-SiCN ceramics, together with additive manufacturing, enable the integration of material, structure and function within a single component. [ABSTRACT FROM AUTHOR]

• To review on development of magnesium and its alloys. • To investigate multiple biomedical applications of magnesium-based materials including orthopedic implants, cardiovascular implants, biodegradable surgical wires, staplers, and their anti-tumor activity. • To explore magnesium alloys functional properties such as biocompatibility, density, mechanical properties, corrosion resistance in biomedical environment, ductility, nontoxicity, host tissue response, and various anti-microbial strategies. • To peruse different surface modification and advanced manufacturing technologies of magnesium and its alloy to improve biomedical properties. • To survey magnesium and its alloy for biomedical applications and future direction. Magnesium (Mg) and its alloys have recently gained increasing attention in the biomedical field as promising biodegradable materials with harmless degradation products. Magnesium-based alloys have a wide range of biomedical applications because of their outstanding biocompatibility and unique mechanical properties. Widespread use of Mg-based biomedical devices eliminates the need for post-healing biomaterial removal surgery and minimizes the negative consequences of the implantation of permanent biomaterials, including stress shielding and undesired metal ion release in the body. This paper provides a literature review on the properties and manufacturing methods of Mg-based alloys for biomedical applications, including orthopedic implants, cardiovascular applications, surgical wires and staplers, and antitumor activities. Each application of Mg-based biomaterials is investigated from a biological perspective, including matching functional properties, biocompatibility, host tissue responses, and anti-microbial strategies, along with potential additive manufacturing technologies for these applications. Finally, an outlook is presented to provide recommendations for Mg-based biomaterials in the future. [Display omitted] [ABSTRACT FROM AUTHOR]

Additive manufacturing processes for the production of large structural components, such as wire arc additive manufacturing (WAAM), offer great manufacturing potential due to their flexibility and design freedom, e.g. for the automotive industry. In order to achieve the desired surface and properties of the surface zone, additive manufacturing is usually followed by mechanical finishing. In this paper, the influence of the process parameters during WAAM and deep rolling (DR) on the residual stresses and the lifetime of AlSi12 components is investigated. Knowledge of the interactions between the process parameters in WAAM and DR as well as their effect on the surface zone properties and the application behavior is elementary. This enables the prediction of the component properties and quality. With the help of the appropriate selection of the process parameters, the residual stress state and the service life can be increased in such a way that components with high fatigue strength can be manufactured. This results in an average increase in service life of up to 17.8 times. [ABSTRACT FROM AUTHOR]

Coherence scanning interferometry (CSI), based on the principle of interference, can achieve sub-nanometer precision for height measurements. On the other hand, focus variation microscopy (FVM), combining the small depth of field of the objective, is a widely used surface topography measurement method suited to surface topography that is mostly optically rough. In this paper, we propose a method to simultaneously obtain the interferometric fringe data and focus variation FVM image stack, from a single vertical scanning process, using a CSI instrument without any hardware modifications. Using a 3D Fourier transform, the FVM signal, looks takes the form of a "bowtie" and the CSI signal resembles two "umbrellas" that are separated in 3D K-space. The signal is recovered using a 3D inverse Fourier transform and the surface topography can be determined by fusing the CSI and FVM signals. Since both signals come from the same instrument and scanning process, there is no need for coordinate registration and data interpolation during the data fusion process. Our method combines the features of CSI and FVM measurement, thereby improving the robustness and data coverage of the measurement. An all-in-focus surface topography map can also be generated using this method. This focusing feature has the potential to significantly improve the defect detection and quality control ability of CSI instruments. • Extracting focus variation data from coherence scanning interferometry without any hardware modifications. • No need for coordinate registration and data interpolation during the data fusion process. • Combining the features of CSI and FVM measurement, thereby improving the robustness and data coverage of the measurement. • All-in-focus surface topography map can be generated using this method for defect detection and quality control. [ABSTRACT FROM AUTHOR]

• The progress made in the application of DED technology to Mg-alloys has been evaluated. • The predominant imperfections, notably inhomogeneous microstructure evolution, and porosity, observed in Mg-alloy components manufactured through DED are discussed. • The preventive measures implemented to counteract the formation of these defects are explored. • The challenges and prospects of DED of Mg-alloys are summarized. Mg-alloys have gained considerable attention in recent years for their outstanding properties such as lightweight, high specific strength, and corrosion resistance, making them attractive for applications in medical, aerospace, automotive, and other transport industries. However, their widespread application is hindered by their low formability at room temperature due to limited slip systems. Cast Mg-alloys have low mechanical properties due to the presence of casting defects such as porosity and anisotropy in addition to the high scrap. While casting methods benefit from established process optimization techniques for these problems, additive manufacturing methods are increasingly replacing casting methods in Mg alloys as they provide more precise control over the microstructure and allow specific grain orientations, potentially enabling easier optimization of anisotropy properties in certain applications. Although metal additive manufacturing (MAM) technology also results in some manufacturing defects such as inhomogeneous microstructural evolution and porosity and additively manufactured Mg alloy parts exhibit lower properties than the wrought parts, they in general exhibit superior properties than the cast counterparts. Thus, MAM is a promising technique to produce Mg alloy parts. Directed energy deposition processes, particularly wire arc directed energy deposition (WA-DED), have emerged as an advantageous additive manufacturing (AM) technique for metallic materials including magnesium alloys, offering advantages such as high deposition rates, improved material efficiency, and reduced production costs compared to subtractive processes. However, the inherent challenges associated with magnesium, such as its high reactivity and susceptibility to oxidation, pose unique hurdles in the application of this technology. This review paper delves into the progress made in the application of DED technology to Mg-alloys, its challenges, and prospects. Furthermore, the predominant imperfections, notably inhomogeneous microstructure evolution and porosity, observed in Mg-alloy components manufactured through DED are discussed. Additionally, the preventive measures implemented to counteract the formation of these defects are explored. [Display omitted] [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) processes with their tool-free production process and low infrastructural requirements, such as the Fused Layer Modeling process, make it possible to decentralize production capacities and thus enable distributed production. Companies and scientists expect these to increase resilience and reduce the ecological footprint. This paper focuses on the site selection of distributed additive production networks. By transforming the location planning in AM into a two-level uncapacitated facility location problem, a developed algorithmic approach based on k-means clustering can identify optimized factory distributions. This paper discusses the role and interdependence of costs, pollution and resilience in the selection process of a factory network planning. It shows the interaction between the factor costs leading to low and pollution as well as resilience leading to highly distributed manufacturing. Furthermore, possible approaches to identify optimal factory distributions, upcoming future changes in environmental politics and major advantages of distributed AM are discussed. This paper will support companies and researcher aiming for distributed resilient production using AM. The findings of this paper and parts of the approach can be used for other production technologies such as distributed production through maker spaces or factories with an equally capable machine park. Through the findings of this paper current production networks such as centralized conventional manufacturing can be compared with distributed AM networks. [ABSTRACT FROM AUTHOR]

Additive Manufacturing (AM) technologies give more and more design freedom to designers and engineers to define and fabricate highly complex functional geometries and material compositions by using advanced Design for AM (DfAM) methods, such as generative design, lattice structure configuration, and bio-inspired design. However, it is still hard for designers to realize a complex design with ensured manufacturability via the use of a single DfAM method, especially for some complex functional lightweight structures. To fully exploit the advantages of AM processes, this paper proposes a new hybrid generative design method, which combines many existing DfAM methods and printing preparation optimization methods. Firstly, functional features are designed and analyzed with the use of AM processing knowledge and numerical simulation. Then, lattice structure configuration is used to achieve a lightweight and qualified part consolidation. In this process, to avoid the cumbersome AM preprocessing stages, support point determination and bio-inspired support generation methods are integrated into the part consolidation design stage. Finally, multiple designed volumes, realized by using different methods, are combined into a complete single structure. To demonstrate the applicability of the proposed method, a design case of a complex functional hydraulic component is presented at the end of the paper. [ABSTRACT FROM AUTHOR]

The advent of new psychoactive substances (NPS) has caused enormous difficulty for legal control since they are rapidly commercialized, and their chemical structures are routinely altered. In this aspect, derivatives phenethylamines, such as 25E-NBOH, have received great attention in the forensic scenario. Hence, we propose portable and cost-effective (U$ 5.00) 3D-printed devices for the electrochemical screening of 25E-NBOH for the first time. The cell and all electrodes were printed using acrylonitrile butadiene styrene filament (insulating material) and conductive filament (graphite embedded in a polylactic acid matrix), respectively, both by the fused deposition modeling (FDM) 3D printing technique. The electrochemical apparatus enables micro-volume analysis (50–2000 μL), especially important for low sample volumes. A mechanistic route for the electrochemical oxidation of 25E-NBOH is proposed based on cyclic voltammetric data, which showed two oxidation processes around +0.75 V and +1.00 V and a redox pair between +0.2 and −0.2 V (vs. graphite ink pseudo-reference). A fast and sensitive square-wave voltammetry method was developed, which exhibited a linear working range from 0.85 to 5.1 μmoL−1, detection limit of 0.2 μmol L−1, and good intra-electrode precision (n = 10, RSD <5.3 %). Inter-electrode measurements (n = 3, RSD <9.8 %) also attested that the electrode production process is reproducible. Interference tests in the presence of other drugs frequently found in blotting paper indicated high selectivity of the electrochemical method for screening of 25E-NBOH. Screening analysis of blotting paper confirmed the presence of 25E-NBOH in the seized samples. Moreover, a recovery percentage close to 100 % was found for a spiked saliva sample, suggesting the method's usefulness for quantitative purposes aimed at information on recent drug use. [Display omitted] • The fully 3D-printed electrochemical device is proposed for on-site forensic analysis. • All electrodes were manufactured using a lab-made graphite-based filament. • The electrochemical system enables analysis with a minimal sample volume (200 μL). • Electrochemical screening of 25E-NBOH in real-world forensic samples. • Selectivity was achieved even in the presence of other drugs found alongside 25E-NBOH. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) food printing is an emerging trend in additive manufacturing and rapid prototyping. Based on a real-world scenario originating from 3D-printed food manufacturing, this paper investigates a single vacation queue with a connected fluid-type inventory. In such an integrated system, customers' orders for personalized products arrive following a Poisson process, and the first-in-first-out principle governs the service discipline at the service facility. Since some raw materials used in food manufacturing are stored in fluid form, the quantity required for each customer is no longer unit-sized. We suppose that each customer consumes an exponential amount of items upon service completion. When the stock becomes empty, the server leaves the system on vacation and hires specialists to adjust and maintain the processing equipment during this time. Adopting the well-known (s , S) control policy, internal production with an exponential lead time is used to replenish the inventory. Under the assumption that customers who arrive during the stock-out period and the remaining vacation time are lost, we derive the explicit product form solution for the system state joint distribution by converting integral equations to equivalent ordinary differential equations. Furthermore, with the help of these joint probability distributions, mathematical formulas are also developed to estimate system performance metrics. Finally, incorporating these metrics into a cost function, an optimal (s , S) inventory policy and its corresponding minimum cost can be numerically determined. • Production fluid-type inventory model originating from 3D-printed food manufacturing is constructed. • Server's vacation mechanism is firstly introduced into production fluid-type inventory model. • The explicit product form solution for the system state joint distribution is derived. • A concise method for solving Kolmogorov forward equation with integral terms is demonstrated. • The optimal (s, S) inventory policy and its corresponding minimum cost rate are numerically studied. [ABSTRACT FROM AUTHOR]

Digital light processing (DLP), derived from stereolithography (SL), is a lithography-based additive manufacturing (AM) process that offers the ability to tailor scaffold shape, size, material, and biometrics of fabricated scaffolds to patient requirements. The additive manufacturing of tricalcium phosphate (TCP) bioceramic scaffolds via DLP is explored in the proceeding research paper. Particularly, the role of exposure intensity and exposure time on resultant scaffold quality and mechanical properties is studied. Increased exposure intensity results in an increased deviation from the designed lattice structure and thus an increase in compressive strength. Scaffolds produced with the highest exposure intensity, resulted in a 27.6 % error increase in mean beam diameter, resulting from an increased scattering effect, penetration depth, and over-curing of peripheral slurry. TCP scaffolds with an exposure time of 3.5 s and exposure intensity of 40 mW/cm2 possessed the highest print accuracy, resulting in the lowest average compressive strength – 82 MPa for the scaffolds of cube structure and 48 MPa for the ones of I-WP structure. Digital light processing (DLP) is an effective additive manufacturing (AM) method applicable for bioceramics. This study focuses on the influence of light exposure intensity on scaffold quality and compressive strength. The increase of exposure intensity can improve the compressive strength with the sacrifice of structure accuracy. The conclusions of this study can provide insights into the relationship of DLP printing parameters and scaffolds quality. [Display omitted] [ABSTRACT FROM AUTHOR]

Owing to the unique technological merits of additive manufacturing (AM), design for AM, particularly eco-design for AM, has been gaining attention in improving the sustainable performance of AM-fabricated (AMed) parts. The main challenge in harvesting potential sustainability benefits is how to capture the impact of design on sustainable performance. Though several existing studies adopted quantitative evaluation on AM sustainability and investigated the relationships between design information and sustainability information of AMed part, the sustainability information is still unavailable in the design phase. This hardly guides eco-design for AM in practice. To support the increasing industrial applications of AM, this paper illustrates related knowledge, that is, material-process-structure-ecoProperty (MPSeP) relationships to connect design and sustainability information in eco-design for AM. An ontology-based method is proposed to model the MPSeP relationships of the AMed part in a structured way. An example of an AMed hydraulic valve body was used to demonstrate the MPSeP modeling process. It is discussed that how the constructed model effectively assists AM designers through providing eco-design recommendation, and enables design software tools to perform sustainability analysis towards eco-design for AM. [ABSTRACT FROM AUTHOR]

The resource consumption of products and production processes, regarding energy and material, is the most important parameter in assessing economic and ecological sustainability. Existing approaches for measuring resource consumption calculate key performance indicators, such as the carbon footprint, from which actions can be derived. The data acquisition, processing, and visualization are usually complex and individually adapted to the products and production machines. This paper presents a method to capture the resource consumption of a product and production machine with low effort and in a targeted manner to calculate the carbon footprint subsequently. The approach's novelty lies in linking any sensor technology with a cross-platform application, integrating existing data sets, and incorporating gamification techniques. Gamifying the process, users engage more with the data, leading to higher awareness and deeper insights. The application offers an intuitive user interface displaying resource consumption by calculating the environmental impact of the production. The live data integration allows for immediate monitoring of the effect of adaptions to the production process, that helps to create a better understanding of contributions to resource consumption. The use of the application is highlighted in a case study of industrial complexity. [ABSTRACT FROM AUTHOR]

The environmental impact of new products and production processes is one of the most important indicators of the current time. Many methods exist to estimate ecological metrics, such as the Product Carbon Footprint (PCF) in the individual product development phases with stand-alone software. However, methods to integrate the PCF in the entire process chain with the possibility to interact in the process are missing. This paper presents a new approach to measuring the ecological impact of an Additive Manufacturing production process, exemplified by the Material Extrusion (MEX) process. The novelty of the approach lies in implementing a single software for machine control, processing, and visualization of sensor signals, parameter variation, and reporting functions to enable comprehensive PCF management. The workflow includes a model-based prediction of the PCF based on the G-code, live monitoring during the production phase, and a subsequent automated evaluation at a central interface. Critical points can be identified, and approaches for optimizing the MEX process can be designed. Uncertainty evaluation of the PCF based on the combination of uncertainty of the sensors and the Life Cycle Assessment is included in the method. The developed prototype software can be used in the design phase for prediction and in the process phase for optimization, enabling seamless PCF management for the MEX process. [ABSTRACT FROM AUTHOR]

Additive manufacturing creates parts by depositing a preform, typically layer by layer. Subtractive manufacturing involves removing material from a preform to create parts. Hybrid machine tools combine both additive and subtractive processes in the same workspace. They can be used to create parts that meet functional tolerance and surface finish requirements, or to create features that are difficult to produce using additive or subtractive processes alone. This paper describes hybrid metal additive/subtractive machine tools. It covers design considerations, sensors and controls, process management, programming and software, and the impact on the design space. It also identifies future research challenges. [ABSTRACT FROM AUTHOR]

Understanding the impact of hydrogen embrittlement (HE) on the mechanical properties of additively manufactured (AM) metals is of utmost importance for industries utilizing these materials, including critical hydrogen transportation and storage applications. This comprehensive review paper explores the effects of HE on AM alloys, emphasizing the crucial role of microstructure and its influence on HE and hydrogen-induced crack initiation (HICI) and propagation processes. Recent studies indicate that the HE in AM metals may deviate from that observed in conventionally manufactured (CM) metals. The unique characteristics of AM processes may introduce additional factors that affect the complex hydrogen-materials interactions and HE. The hydrogen accumulation at phase interfaces and local reaching of the critical hydrogen concentration represents the primary reason for HICI in AM metals. The specific microstructure of AM and interfaces between phases in the microstructure present crucial factors that influence the HE of AM metals. The interface between phases, which serves as a material structure discontinuity and a location for misfit energy within the structure, can play a critical role in the drop of the HE resistance of certain materials (e.g., martensite/austenite interface in stainless steels, ferrite/perlite interface in low carbon steels, α/β interface in titanium alloys, γ ′ / γ ″ interface in nickel-based alloys, etc.). Titanium and nickel alloys demonstrate comparable microstructural features concerning HE due to the laminar phase structure that develops during heat treatment and the secondary phase allotropy in both metals. However, stainless steels, such as SS316 and SS304, follow a distinct mechanism where austenite to martensite transformation predominantly governs hydrogen embrittlement. It is noteworthy that the effect of hydrogen embrittlement in additively manufactured metals seems to be less pronounced compared to CM metals. A comprehensive investigation of HE mechanisms and their interaction with microstructure according to the HELP + HEDE model can provide valuable insights into the susceptibility of AM metals to HE and HICI. This review underscores the need for continued investigation to ensure the reliable performance of AM metal components exposed to hydrogen and HE in various industrial applications. Also, it provides an in-depth understanding of hydrogen embrittlement in AM metals, providing recommendations for the design, development, and safety introduction of new additively manufactured alloys in hydrogen-based energy solutions. Finally, a perspective on future necessary experiments for exploring the influence of porosity in AM metals on HE, hydrogen-induced crack initiation, and other hydrogen damage mechanisms, including its interaction with microstructure, is given. [Display omitted] • Viewing hydrogen embrittlement (HE)'s impact on mechanical properties in additive manufacturing features its key roles. • Emphasizing the complexity of HE in AM alloys, urging ongoing investigations in hydrogen-rich environments. • Examining AM metals reveals varying HE behavior by alloy (e.g., titanium, nickel superalloys, austenitic stainless steel). • Assessing the microstructure's crucial role in quantifying HE in AM metals. • Exploring innovative solutions for HE in AM alloys in hydrogen-rich environments (e.g., aerospace). [ABSTRACT FROM AUTHOR]

The paper offers a comprehensive exploration of 3D printing silicon carbide, covering its advantages over traditional manufacturing, potential applications across industries, environmental considerations, and the market's perspective. This holistic approach provides valuable insights into the expanding applications of silicon carbide ceramics and underscores the significance of this technology in various sectors. While 3D printing of silicon carbide offers many advantages, including precision and customization, it also faces several significant challenges related to material properties, process optimization, post-processing, cost, quality control, and environmental considerations. Addressing these challenges is essential for the widespread adoption and success of silicon carbide 3D printing technology across various industries. [ABSTRACT FROM AUTHOR]

Even though computational design has paved the way for the design of complex forms, construction is still difficult, inefficient, and costly. This paper aims to compile the most recent fabrication techniques for shell structures to create an overview of fabrication methods. This paper reviews existing, recently developed, and previously unexplored techniques for building and fabricating shell structures. The objective of this review is to find trends, patterns, or gaps in the literature that can direct future research. As a result, each fabrication technique is explained and demonstrated with relevant built projects. Moreover, each method's advantages, disadvantages, and limitations are highlighted. These techniques are grouped into four main classes and evaluated. In conclusion, categorizing fabrication techniques reveals the state-of-the-art in fabrication and highlights potential research gaps. Moreover, this research might encourage researchers to explore novel methods and solutions to overcome the current method's limitations. • The state-of-the-art fabrication techniques for shell structures are presented. • A comprehensive, up-to-date literature review of fabrication methods is presented. • The methods of fabrication are classified in an exclusive manner. • The pros and cons of fabrication techniques are discussed. • This review highlights the current gaps in fabrication methods. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) has undergone significant development over the past decades, resulting in vast amounts of data that carry valuable information. Numerous research studies have been conducted to extract insights from AM data and utilize it for optimizing various aspects such as the manufacturing process, supply chain, and real-time monitoring. Data integration into proposed digital twin frameworks and the application of machine learning techniques is expected to play pivotal roles in advancing AM in the future. In this paper, we provide an overview of machine learning and digital twin-assisted AM. On one hand, we discuss the research domain and highlight the machine-learning methods utilized in this field, including material analysis, design optimization, process parameter optimization, defect detection and monitoring, and sustainability. On the other hand, we examine the status of digital twin-assisted AM from the current research status to the technical approach and offer insights into future developments and perspectives in this area. This review paper aims to examine present research and development in the convergence of big data, machine learning, and digital twin-assisted AM. Although there are numerous review papers on machine learning for additive manufacturing and others on digital twins for AM, no existing paper has considered how these concepts are intrinsically connected and interrelated. Our paper is the first to integrate the three concepts big data, machine learning, and digital twins and propose a cohesive framework for how they can work together to improve the efficiency, accuracy, and sustainability of AM processes. By exploring latest advancements and applications within these domains, our objective is to emphasize the potential advantages and future possibilities associated with integration of these technologies in AM. • Explored how additive manufacturing evolution yields big data, leveraging ML and DT to optimize manufacturing. • Discussed the interconnection among big data, machine learning, and digital twins. • Examined ML's role in material analysis, design optimization, process optimization, defect detection, and sustainability. • Reviewed current developments for the application of digital twins to empower additive manufacturing. [ABSTRACT FROM AUTHOR]

Additive manufacturing is a promising and resource-efficient construction method, applying material only where needed. Demand for these processes in construction is growing, but research into their use in timber construction is limited. The 3DWoodWind project explores additive application methods using thin wood veneer strips. Robotic winding processes can be used to develop wood-based hollow parts with minimal material input and optimised structural properties. This paper presents a modular building system of robotically wound column and slab components, including a brief description of the structural design and material system, with a focus on the manufacturing process. It covers in detail robotic fabrication, customised end-effector design, formwork system development, computational design methods, and the integration of a fully automated adhesive application system. A full-scale prototype roof structure demonstrates the manufacturing process and reusability concept in various architectural applications. The paper concludes by discussing the building system's potential and areas for further research. • Additive application methods of wood veneer as a sustainable alternative to synthetic fibres. • Three-dimensional robotic winding processes for material-efficient lightweight components. • Production of a modular column and ceiling system for large-scale applications. • Computational design methods for filament layup and fibre orientation. • Highly automated robotic fabrication technique with customised end-effector design. [ABSTRACT FROM AUTHOR]

Nano and micro-porous structures exhibit intriguing properties for a wide variety of applications, spanning from the biomedical to sensing. However, their fabrication is a challenge in terms of dimensional accuracy, which affects devices' performance and sensitivity. In this paper, we present a route to enhance the dimensional accuracy of fabrication via Stereolithography (SLA) of porous features at the micro-scale. Using a custom benchmark part, deviations in feature dimensions (micro-pores diameters and depths) were measured by confocal microscopy. Sample characterization and experimental observations allowed the identification of inaccuracy sources (i.e., laser spot size and its compensation on path generation), and a compensation method of the nominal laser spot diameter (85|um) was defined. Implementing such a method results in relevant improvements in dimensional accuracy: 9.8% and 11.3% on full-open pores diameter and depth, respectively. Partially open pores accuracy improvements were 15.8% on diameters and 1.5% on depths. Since machine optical equipment can result in deviations in the actual laser spot diameter from the nominal value, the actual laser beam spot diameter was estimated by printing a test part and adopting this information to adjust a calibration procedure. The measurements revealed that the actual laser beam spot size is 93±8um. The proposed method can be extended for the fabrication of any micro-porous structures. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on the advancements and potential of industrial robots in the field of additive manufacturing of thermoplastics. As the manufacturing industry continues to embrace Industry 4.0 and smart manufacturing principles, the integration of robotic systems has gained significant attention due to their flexibility, precision, and automation capabilities. This article explores the utilization of industrial robots in achieving free-form fabrication, particularly focusing on the additive manufacturing process for composite materials. It looks into the hardware setup, software systems configuration, and platform development that combines FDM with robotic arm technologies. It discusses the merits, limitations, and prospective uses of freeform additive manufacturing and the interoperability between traditional additive manufacturing and robotic additive manufacturing. The experimental results show that this integration is feasible and advantageous, with better process flexibility and production capacities when compared to typical FDM systems. [ABSTRACT FROM AUTHOR]

The study discussed in this paper focuses on additive manufacturing (AM) of intricate geometrically structured components of a prosthetic leg. The objective is to optimize the original design to reduce the need for support structures while maximizing stiffness and reducing weight. Making a prosthetic leg lighter can improve the mobility of a person and reduce the energy required to climb stairs, enhancing their quality of life and independence. Traditional manufacturing methods, such as injection molding and computerized numerical control (CNC) machining, have limitations in terms of design flexibility. The study used Selective Laser Melting (SLM) technology with 316L-A stainless steel powder. The optimization process focused on the knee, upper leg, lower leg, hydraulic, and oil support system. The workflow procedure for additive manufacturing was discussed. Overall, the study successfully reduced the weight of the prosthetic leg by 50% from the original model. [ABSTRACT FROM AUTHOR]

This paper examines the current landscape of ontologies for describing additive manufacturing (AM) technologies and services. Through an extensive search, using both a bottom-up and top-down approach, four accessible AM ontologies were identified. These ontologies were then evaluated according to generally accepted principles and guidelines. It was found, that two of the four ontologies could deal as a starting point for a semantic core of a B2B AM services matchmaking platform. To remedy the existing problems of impracticability, underdevelopment, and lacking linkage to other ontologies, we see a gap in regathering of AM data in a FAIR and sustainable way, and deploying a re-engineered version of a candidate ontology. [ABSTRACT FROM AUTHOR]

Laser Powder Directed Energy Deposition (LP-DED) is a promising Additive Manufacturing (AM) technology that offers the opportunity of repairing and revamping damaged or outdated parts and molds. Notwithstanding, it should be considered that the low surface quality of the produced parts makes post-processing operations necessary in order to meet the industrial requirements, and these operations strongly depend on the accuracy of the produced parts. In this paper, firstly an artifact for the LP-DED process, including classical features with and without curvatures, is proposed. Then, the dimensional accuracy and geometrical tolerances of the features are evaluated, limited to AISI 316L stainless steel. The findings of this work showed that the dimensional and geometrical tolerances of the LP-DED process are comparable with those of sand casting. On the other hand, tolerances are lower compared to Laser Beam Powder Bed Fusion (LB-PBF) technologies but are similar to those observed in Electron Beam Powder Bed Fusion (EB-PBF). • A 316L stainless steel artifact is designed. • The IT tolerance grade of the LP-DED process varies between IT15 and IT17, and lower IT value is obtained for larger basic size. • The IT tolerance grade strongly depends on the geometry of the feature. • Considering geometrical tolerances, surface profile error is about 1 mm, angularity error is about 0.3 deg. • And other geometrical tolerances are lower than 0.6 mm. • Higher errors are associated with larger geometries. [ABSTRACT FROM AUTHOR]

In comparison to conventional manufacturing technologies, additive manufacturing (AM) offers great design freedom, the integration of functions into components, new lightweight design concepts and high material efficiency. In aerospace and turbomachinery, this technology is increasingly coming into focus, especially the laser-based powder bed fusion of metals (PBF-LB/M) process. PBF-LB/M is already used for some aerospace components, which are often exposed to high thermal and mechanical loads. Dependent on the component geometry, support structures are required for AM, which then usually have to be removed by machining. One suitable support structure is the use of material with specifically induced porosity. This ensures good heat dissipation and thus homogeneous component properties, high retention forces and short process times in PBF-LB/M. However, the machinability of porous, additively manufactured material has hardly been researched so far. One preliminary investigation of milling porous, additively manufactured Inconel 718, though, showed significantly poorer machinability of the porous material compared to the dense material. To further examine this phenomenon, this paper presents the results of fundamental machinability studies with porous, additively manufactured Inconel 718 in orthogonal cutting. The investigations with tungsten carbide cutting tools on a special fundamental test rig include the analysis of the cutting force, the chip geometry, the chip temperature and the surface quality. The research results provide explanations for the poorer machinability of the porous material and derived approaches for improving the machinability in future studies. [ABSTRACT FROM AUTHOR]

Additive manufacturing facilitates the materialization of complex designs, e.g. bio-inspired non-assembly joints. Despite the advantages of this type of joints, such as single-step manufacturing, their performance under operational conditions remains poorly understood. This paper explores the design, fabrication and wear performance of a hinge-type joint inspired by the camel elbow. The joint was fabricated by metal additive manufacturing and its wear behaviour was numerically and experimentally evaluated. The results show that the bio-inspired design performs better than a cylindrical one in terms of wear distribution. This work helps to better understand the wear performance of non-assembled bio-inspired joints. [ABSTRACT FROM AUTHOR]